Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set

Photocatalytic degradation of antibiotic sulfamethizole by visible light activated perovskite LaZnO3

In this work, the perovskite LaZnO3 was synthesized via sol-gel method and applied for photocatalytic treatment of sulfamethizole (SMZ) antibiotics under visible light activation. SMZ was almost completely degraded (99.2% ± 0.3%) within 4 hr by photocatalyst LaZnO3 at the optimal dosage of 1.1 g/L, with a mineralization proportion of 58.7% ± 0.4%. The efficient performance of LaZnO3 can be attributed to its wide-range light absorption and the appropriate energy band edge levels, which facilitate the formation of active agents such as ·O2-, h+, and ·OH. The integration of RP-HPLC/Q-TOF-MS and DFT-based computational techniques revealed three degradation pathways of SMZ, which were initiated by the deamination reaction at the aniline ring, the breakdown of the sulfonamide moieties, and a process known as Smile-type rearrangement and SO2 intrusion. Corresponding toxicity of SMZ and the intermediates were analyzed by quantitative structure activity relationship (QSAR), indicating the effectiveness of LaZnO3-based photocatalysis in preventing secondary pollution of the intermediates to the ecosystem during the degradation process. The visible-light-activated photocatalyst LaZnO3 exhibited efficient performance in the occurrence of inorganic anions and maintained high durability across multiple recycling tests, making it a promising candidate for practical antibiotic treatment.

Construction of Au quantum dots/nitrogen-defect-enriched graphite carbon nitride heterostructure via photo-deposition towards enhanced nitric oxide photooxidation

The challenge of mitigating pollution stemming from industrial exhaust emissions is a pressing issue in both academia and industry. This study presents the successful synthesis of nitrogen-defect-enriched graphite carbon nitride (g-C3N4) using a two-step calcination technique. Furthermore, a g-C3N4-Au heterostructure was fabricated through the photo-deposited Au quantum dots (QDs). When subjected to visible light irradiation, this heterostructure exhibited robust nitric oxide (NO) photooxidation activity and stability. With its fluffy, porous structure and large surface area, the nitrogen-defect-enriched g-C3N4 provides more active sites for photooxidation processes. The ability of g-C3N4 to absorb visible light is enhanced by the local surface plasmon resonance (LSPR) effect of Au QDs. Additionally, the lifetime of photogenerated charge carriers is extended by the presence of N defects and Au, which effectively prevent photogenerated electron-hole pairs from recombining during the photooxidation process. Moreover, the oxidation pathway of NO was analyzed through In-situ Fourier transform infrared (FT-IR) spectroscopy and Density Functional Theory (DFT) calculation. Computational findings revealed that the introduction of Au QDs decreases the activation energy of the oxidation reaction, thereby facilitating its occurrence while diminishing the formation of intermediate products. As a result, NO is predominantly converted to nitrate (NO3-). This work unveils a novel approach to constructing semiconductor-cocatalyst heterostructures and elucidates their role in NO photooxidation.

Covalent organic frameworks derived Single-Atom cobalt catalysts for boosting oxygen reduction reaction in rechargeable Zn-Air batteries

The design and development of high-performance and long-life Pt-free catalysts for the oxygen reduction reaction (ORR) is of great important with respect to metal-air batteries and fuel cells. Herein, a new low-cost covalent organic frameworks (COFs)-derived CoNC single-atoms catalyst (SAC) is fabricated and compared with the engineered nanoparticle (NP) counterpart for ORR activity. The ORR performance of the SAC catalyst (CoSA@NC) surpasses the NP counterpart (CoNP-NC) under the same operation condition. CoSA@NC also achieves improved long-term durability and better methanol tolerance compared with the Pt/C. The zinc-air battery assembled by the CoSA@NC cathode delivers a higher power density and energy density than that of commercial Pt/C catalyst. Molecular dynamics (MD) is performed to explain the spontaneous evolution from clusters to single-atom metal configuration and density functional theory (DFT) calculations find that CoSA@NC possesses lower d-band center, resulting in weaker interaction between the surface and the O-containing intermediates. Consequently, the reductive desorption of OH*, the rate-determine step, is further accelerated.

Construction and catalysis role of a kinetic promoter based on lithium-insertion technology and proton exchange strategy for lithium-sulfur batteries

The high theoretical energy density and specific capacity of lithium-sulfur (Li-S) batteries have garnered considerable attention in the prospective market. However, ongoing research on Li-S batteries appears to have encountered a bottleneck, with unresolved key technical challenges such as the significant shuttle effect and sluggish reaction kinetics. This investigation explores the catalytic efficacy of three catalysts for Li-S batteries and elucidates the correlation between their structure and catalytic impacts. The results suggest that the combined utilization of lithium-insertion technology and a proton exchange approach for δ-MnO2 can optimize its electronic structure, resulting in an optimal catalyst (H/Li inserted δ-MnO2, denoted as HLM) for the sulfur reduction reaction. The replacement of Mn sites in δ-MnO2 with Li atoms can enhance the structural stability of the catalyst, while the introduction of H atoms between transition metal layers contributes to the satisfactory catalytic performance of HLM. Theoretical calculations demonstrate that the bond length of Li2S4 adsorbed by the HLM molecule is elongated, thereby facilitating the dissociation process of Li2S4 and enhancing the reaction kinetics in Li-S batteries. Consequently, the Li-S battery utilizing HLM as a catalyst achieves a high areal specific capacity of 4.2 mAh cm-2 with a sulfur loading of 4.1 mg cm-2 and a low electrolyte/sulfur (E/S) ratio of 8 μL mg-1. This study introduces a methodology for designing effective catalysts that could significantly advance practical developments in Li-S battery technology.

Coordinated d-p hybridized hcp@fcc NiRu alloy doped by interstitial atoms for boosting urea-assisted simulated seawater electrolysis at industrial current densities

The production of hydrogen through seawater electrolysis has recently garnered increasing concern. However, hydrogen evolution reaction (HER) by alkaline seawater electrocatalysis is severely impeded by the slow H2O adsorption and H* binding kinetics at industrial current densities. Herein, a face-centered cubic/hexagonal close packed (fcc/hcp) NiRu alloy heterojunction was fabricated on Ni foam (N doped NiRu-inf/NF) by a low-temperature nitrogen plasma activation. Simultaneously, nitrogen atoms are introduced into the alloy to facilitate d-p hybridization. When N doped NiRu-inf/NF is integrated into a dual-electrode cell for urea-assisted seawater electrolysis, it achieves 100 mA cm-2 with an ultra-low voltage of 1.36 V and excellent stability. Density functional theory (DFT) verifies that the robust d-p hybridization among Ni, Ru and N exhibits more energy level matching for H2O molecule adsorption at the Ru sites, while simultaneously reducing the interaction between H* and Ni sites in N-doped NiRu-inf.

Interfacial engineering layered bimetallic oxyhydroxides for efficient oxygen evolution reaction

Transition metal-based oxyhydroxides (MOOH) have garnered significant attention as promising catalyst for the Oxygen Evolution Reaction (OER). However, the direct synthesis of MOOH poses challenges due to the instability of trivalent cobalt and nickel salts, attrivuted to their high oxidation states. In this study, theoretical computations predicted that Co(OH)2 nanosheets are exclusively formed on carbon structures, owing to the stronger binding energy between CoOOH and CC compared to Co(OH)2. Furthermore, the presence of FeOOH interface reduces the binding energy between CoOOH and carbon structure. Experiment evidence confirms that CoOOH can be directly synthesized through controlled epitaxial growth on an FeOOH interface using a hydrothermal method. Moreover, the in-situ doping of iron leads to the formation of high-quality Fe0.35Co0.65OOH with exceptional OER performance, displaying a low overpotential of 240 mV at 10 mA cm-2 and a small Tafel slope of 43 mV dec-1. Density functional theory (DFT) calculations uncover the substantial enhancement of oxygen-containing species adsorption abilities by Fe0.35Co0.65OOH, resulting in improved OER activity. This work presents a promising strategy for the efficient preparation of layered cobalt oxyhydroxides, enabling efficient energy conversion and storage.

Biologically templated formation of Cobalt-Phosphide-Graphene hybrids with charge redistribution for efficient hydrogen evolution

Developing highly efficient and sustainable hydrogen evolution reaction (HER) electrocatalysts is important for the practical application of emerging energy technologies. The spherical structure and phosphorus-rich properties of Chlorella can facilitate the construction of comparable transition metal phosphide electrocatalysts. Here, a microorganism template strategy is proposed to construct a cobalt-phosphide-graphene hybrid. Chlorella can absorb metal ions, and the generated rough spherical nanoparticles are uniformly distributed around the reduced graphene oxide nanosheets. This designed catalyst has comparable HER performance in acidic electrolytes and needs an overpotential of only 153 mV at a current density of 10 mA cm-2. The experimental and density functional theory results imply that the charge redistribution between Co2P and pyrrole-N is the key factor in enhancing the HER activity. The induced electron aggregation at the N and P sites can serve as a key active site for absorbing the adsorbed hydrogen atom intermediate to accelerate the HER process, contributing to the active sites of Co2P- and pyrrole-N-doped carbon with 0 eV hydrogen adsorption free energy. This work provides a broad idea for synthesizing advanced catalysts by a biological template approach, facilitating the innovative integration of biology and emerging electrochemical energy technologies.

Strong interactions through the highly polar "Early-Late" metal-metal bonds enable single-atom catalysts good durability and superior bifunctional ORR/OER activity

Simultaneously enhancing the durability and catalytic performance of metal-nitrogen-carbon (M-Nx-C) single-atom catalysts is critical to boost oxygen electrocatalysis for energy conversion and storage, yet it remains a grand challenge. Herein, through the combination of early and late metals, we proposed to enhance the stability and tune the catalytic activity of M-Nx-C SACs in oxygen electrocatalysis by their strong interaction with the M2'C-type MXene substrate. Our density functional theory (DFT) computations revealed that the strong interaction between "early-late" metal-metal bonds significantly improves thermal and electrochemical stability. Due to considerable charge transfer and shift of the d-band center, the electronic properties of these SACs can be extensively modified, thereby optimizing their adsorption strength with oxygenated intermediates and achieving eight promising bifunctional catalysts for ORR/OER with low overpotentials. More importantly, the constant-potential analysis demonstrated the excellent bifunctional activity of SACs supported on MXene substrate across a broad pH range, especially in strongly alkaline media with record-low overpotentials. Further machine learning analysis shows that the d-band center, the charge of the active site, and the work function of the formed heterojunctions are critical to revealing the ORR/OER activity origin. Our results underscore the vast potential of strong interactions between different metal species in enhancing the durability and catalytic performance of SACs.

Interface engineering enabled by sodium dodecyl sulfonate surfactant for stable Zn metal batteries

Aqueous zinc-ion batteries are emerging as powerful candidates for large-scale energy storage, due to their inherent high safety and high theoretical capacity. However, the inevitable hydrogen evolution and side effects of the deposition process limit their lifespan, which requires rational engineering of the interface between anode and aqueous electrolyte. In this paper, an anionic surfactant as electrolyte additive, sodium dodecyl sulfonate (SDS), is introduced to deliver highly reversible zinc metal batteries. Unlike traditional surfactants, the solvation structure is not affected by SDS, which tends to adsorb on the (002) crystal plane of Zn with the purpose of effectively limiting the water molecules adsorption. Attributed to the natural hydrophobic part of SDS, a dynamic electrostatic shielding layer and a unique hydrophobic interface are constructed on the anode. Assisted by the above merits, the adverse surface corrosion, hydrogen evolution and dendrite growth are significantly inhibited without the sacrifice in the deposition kinetics of Zn ions. As a result, the Zn||Zn symmetric batteries demonstrate an increased cycle life of 2000 h (1 mA cm-2, 1 mA h cm-2) with the presence of SDS additive. Such strategy provides a new avenue for the developing advanced electrolytes to be applied in aqueous energy storage systems.

Novel amorphous FeOOH-modified Co9S8 nanosheets with enhanced catalytic activity in oxygen evolution reaction

Efficient oxygen evolution reaction (OER) is vital for water electrolysis and advanced hydrogen energy production. However, the sluggish kinetics of this reaction require significant overpotentials, leading to high energy consumption. Therefore, developing OER electrocatalysts with exceptional performance and long-term durability is crucial for enhancing the energy efficiency and cost-effectiveness of the hydrogen production process. In this research, novel FeOOH/Co9S8 catalysts were prepared through a two-step hydrothermal reaction followed by one-step electrodeposition on nickel foam for an alkaline OER. The as-obtained catalysts possessed abundant non-homogeneous interfaces between FeOOH and Co9S8 nanosheets, conducive to optimized coordination environments of Fe and Co sites by redistributing interfacial charges. This synergy strengthened the chemisorption of oxygenated intermediates, leading to accelerated reaction kinetics, abundant active sites, and enhanced OER performance. The optimized electrocatalyst FeOOH/Co9S8-15 achieved a current density of 10 mA cm-2 at an overpotential of 248 mV and good stability for over 140 h. This study presents a novel approach for producing compelling and durable alkaline dielectric OER electrocatalysts, which will be helpful in the future manufacturing of advanced energy devices.

Semimetallic state transition in Two-Dimensional carbon nitride covalent networks and enhanced electrocatalytic activity for nitrate to ammonia conversion

Single-atom catalysts (SACs), due to their maximum atomic utilization rate, show tremendous potential for application in the electrocatalytic synthesis of ammonia from nitrate. Yet, the development of superior supports that preserve the high selectivity, activity, and stability of SACs remains an imperative challenge. In this work, based on first-principles calculations and tight-binding (TB) model analysis, a new two-dimensional (2D) carbon nitride monolayer, C7N6, is proposed. The C7N6 structure exhibits a strong covalent network, with dynamical, thermal, and mechanical stability. Surprisingly, the structural transition from C9N4 to C7N6 corresponds to a semimetallic state transition. Further symmetry analysis unveils that the Dirac states in C7N6 are protected by space-time inversion symmetry, and the physical origin of the Dirac cone was confirmed using the TB model. Additionally, a non-zero Z2 invariant and significant topological edge states demonstrate its topologically nontrivial nature. Considering the excellent structural and topological properties of C7N6, a three-step screening strategy is designed to identify eligible SACs for electrochemical nitrate reduction reaction (NO3RR), and Ti@C7N6 is identified as possessing the best activity, with the last proton-electron coupling step *NH2→*NH3 being the potential-determining step (PDS), for which the limiting potential is 0.48 V. Moreover, a free energy diagram shows that the *NOH reaction pathway is energetically preferred on Ti@C7N6, and ab initio molecular dynamics (AIMD) calculations at 500 K confirm its good thermal stability. Our study not only provides excellent CN-based support material but also offers theoretical guidance for constructing highly active and selective SACs for nitrate reduction.

Pb nanospheres encapsulated in metal-organic frameworks-derived porous carbon as anode for high-performance sodium-ion batteries

Alloying-type anode materials are considered promising candidates for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their application is limited by the severe capacity decay stemming from dramatic volume changes during Na+ insertion/extraction processes. Here, Pb nanospheres encapsulated in a carbon skeleton (Pb@C) were successfully synthesized via a facile metal-organic frameworks (MOFs)-derived method and used as anodes for SIBs. The nanosized Pb particles are uniformly incorporated into the porous carbon framework, effectively mitigating volume changes and enhancing Na+ ion transport during discharging/charging. Benefiting from this unique architecture, a reversible capacity of 334.2 mAh g-1 at 2 A g-1 is achieved after 6000 cycles corresponding to an impressive 88.2 % capacity retention and a minimal capacity loss of 0.00748 % per cycle. Furthermore, a high-performance full sodium-ion battery of Pb@C//NVPF was constructed, demonstrating a high energy density of 291 Wh kg-1 and power density of 175 W kg-1. This facile MOFs-derived method offers insights into the design of high-capacity alloy-type anode materials using Pb sources, opening up new possibilities for innovative approaches to Pb recycling and pollution prevention.

Advancing electrochemical nitrogen reduction: Efficacy of two-dimensional SiP layered structures with single-atom transition metal catalysts

Researchers are interested in single-atom catalysts with atomically scattered metals relishing the enhanced electrocatalytic activity for nitrogen reduction and 100 % metal atom utilization. In this paper, we investigated 18 transition metals (TM) spanning 3d to 5d series as efficient nitrogen reduction reaction (NRR) catalysts on defective 2D SiPV layered structures through first-principles calculation. A systematic screening identified Mo@SiPV, Nb@SiPV, Ta@SiPV and W@SiPV as superior, demonstrating enhanced ammonia synthesis with significantly lower limiting potentials (-0.25, -0.45, -0.49 and -0.15 V, respectively), compared to the benchmark -0.87 eV for the defective SiP. In addition, the descriptor ΔG*N was introduced to establish the relationship between the different NRR intermediates, and the volcano plot of the limiting potentials were determined for their potential-determining steps (PDS). Remarkably, the limiting voltage of the NRR possesses a good linear relationship with the active center TM atom Ɛd, which is a reliable descriptor for predicting the limiting voltage. Furthermore, we verified the stability (using Ab Initio Molecular Dynamics - AIMD) and high selectivity (UL(NRR)-UL(HER) > -0.5 V) of these four catalysts in vacuum and solvent environments. This study systematically demonstrates the strong catalytic potential of 2D TM@SiPV(TM = Mo, Nb, Ta, W) single-atom catalysts for nitrogen reduction electrocatalysis.

Theoretical calculations and experimental verification of carbon dioxide reduction electrocatalyzed by metalloporphyrin

Metal-functionalized porphyrin-like graphene structures are promising electrocatalysts for carbon dioxide reduction reaction (CO2RR) as their metal centers can modulate activity. Yet, the role of metal center of metalloporphyrins (MTPPs) in CO2 reaction activity is still lacking deep understanding. Here, CO2RR mechanism on MTPPs with five different metal centers (M = Fe, Co, Cu, Zn and Ni) are examined by first-principles calculations. The *COOH formation is the rate determined step on the five MTPP structures, and the CoTPP exhibits the best CO2RR activity while ZnTPP and NiTPP are the worst, which is also verified by our experiment. The CO2RR activity is controlled by adsorption states of intermediates (*CO, *COOH), i.e., chemisorption (e.g., on CoTPP) and physisorption (on ZnTPP and NiTPP) of intermediates will lead to good and poor activity, respectively. The deeper the d-band center of the porphyrin ring complexed metal atom, the weaker bonding of MTPP with CO and COOH. Theoretical calculations and experimental results indicate that MTPPs with Co and Fe centers lead to a reduction in the energy barriers for the two uphill reaction steps in the electrocatalytic CO2 reduction process, thereby enhancing CO2 reduction electrocatalytic activity. Faradaic efficiency of CO is correlated with the reaction energy barrier of the first proton-coupled electron reduction process, displaying a strong linear correlation. This work provides a fundamental understanding of MTPPs used as electrocatalysts for CO2RR.

Upconversion luminescence through dynamically regulating the depletion of Ho3+: 5I6 level for speed sensing

In this work, a strategy for dynamically adjusting the upconversion luminescence (UCL) color of NaGdF4:Yb3+/Ho3+/Ce3+/Sc3+ is reported based on a phosphor wheel. It has been demonstrated that the rotation-dependent UCL mainly originated from the regulation of depletion mode for the Ho3+: 5I6 level. Due to the dominant linear decay, a high-pure red UCL is observed under the steady-state excitation. However, as the proportion of the steady-state excitation decreases, the green-red emission intensity ratio gradually increases, followed by the color conversion from red to green. An approximate physical model is proposed to understand the dependence of IG/IR on rotation speed. We not only report a UCL material that shows potential application in velocity sensing but also provide new insights into wheel-based dynamic UCL regulation.

Near-unity quantum yield and long-term emission stability in halide perovskite nanocrystal glass composite

Metal halide perovskites are promising optoelectronic materials due to their outstanding luminescent properties. However, the instability of perovskites has long been the bottleneck to their practical applications. Here Cs4PbBr6 nanocrystals based glass composite (Cs4PbBr6 NCs@glass) are successfully prepared, which displays green emission color (520 nm), narrow bandwidth (23 nm) and a near-unity photoluminescence quantum yield (PLQY). The H2O molecules permeating in the lattice of Cs4PbBr6 were found to be a crucial role in the subband energy emission. The Cs4PbBr6 NCs@glass has excellent emission stability; maintains 93 % of initial PL intensity after ultraviolet light irradiation for over 5000 h. In addition, by adjusting the halogen content, we have achieved tunable emission color from blue (450 nm) to green (520 nm) and red (670 nm) on Cs4PbX6 NCs@glass (X = Cl, Br, I), which covers up to 127 % of the National Television Systems Board (NTSC) standard system. Our finding indicates the commercial applications of perovskite materials in lighting and display.

Enhanced conversion of CO2 into C2H4 on single atom Cu-anchored graphitic carbon nitride: Synergistic diatomic active sites interaction

Single atom metal-nitrogen-carbon materials have emerged as remarkably potent catalysts, demonstrating unprecedented potential for the photo-driven reduction of CO2. Herein, a unique Cu@g-C3N5 catalyst obtained by cooperation of single atom Cu and nitrogen-rich g-C3N5 is proposed. The particular CuN diatomic active sites (DAS) in Cu@g-C3N5 contribute to the formation of highly stable CuOCN adsorption, a key configuration for CO2 activation and CC coupling. The synergistic diatomic active sites interaction is found responsible for the efficient photoreduction of CO2 to C2H4 which has been demonstrated in our Gibbs free energy calculation and COHP analysis. The CO2 activation mechanism was studied, the charge density difference and DOS analysis show that the low oxidation state Cu atom significantly affects the electronic structure of g-C3N5 and then enhance the catalytic activity of CO2 hydrogenation.

Facet-dependent activation of oxalic acid over hematite nanocrystals under the irradiation of visible light for efficient degradation of pollutants

Naturally occurring hematite has been widely studied in the Fenton-like system for water pollutant remediation due to its abundance and non-toxicity. However, its inadequate catalytic activity results in difficulty in effectively degrading pollutants in the catalytic degradation system that it constitutes. Thus, we constructed a photochemical system composed of hematite with {001} facet of high activity facet and low-cost and non-toxic oxalic acid (OA) for the removal of various types of pollutants. The removal rate for the degradation of metronidazole, tetracycline hydrochloride, Rhodamine B, and hexavalent chromium by hematite nanoplate with the exposed {001} facet activating OA under visible light irradiation was 4.75, 2.25, 2.33, and 2.74 times than that by the exposed {110} facet, respectively. Density functional theory (DFT) calculation proved that the OA molecule was more easily adsorbed on the {001} facet of hematite than that on the {110} facet, which would favor the formation of the more Fe(III)-OA complex and reactive species. In addition, the reactive site of metronidazole for the attraction of radicals was identified on the basis of the DFT calculation on the molecular occupied orbitals, and the possible degradation pathway for metronidazole included carbon chain fracture, hydroxyethyl-cleavage, denitrogenation, and hydroxylation. Thus, this finding may offer a valuable direction in designing an efficient iron-based catalyst based on facet engineering for the improved activity of Fenton-like systems such as OA activation.

Boosted charge transfer in a naturally formed Ca(Al2Si2O8)/Fe2O3 heterojunction for piezocatalytical formation of H2O2 and solidification of U(VI)

Energy and environmental issues make the generation of H2O2 and the separation of U(VI) from water very important topics. In this work, we disclosed a low-cost, high-efficiency method for separating U(VI) from water based on the naturally formed catalyst (red volcanic stone powders, RVSP) of Ca(Al2Si2O8)/Fe2O3 heterojunction through a piezocatalytic pathway induced by ultrasonication. The charges were found to be elevatedly separated due to the formation of the heterojunction. It is found that under ultrasonication, charges were effectively separated and then reacted with water to form H2O2 with a high yield of 196.7 μmol·g-1 in 4 h, which further solidifies U(VI) to form a solid of UO2O2. The removal rate of U(VI) in water reached 96 % (50 ppm) within 150 min. Furthermore, the results calculated by VASP show that the cyclic variation of the conduction bands under a cyclic force field facilitates the charge separation, and thus may promote piezocatalysis. Most importantly, the application study in real seawater indicates that U(VI) piezocatalysis based on natural minerals has great potential. This work presents a comprehensive investigation of U(VI) piezocatalysis by Ca(Al2Si2O8)/Fe2O3 and provides a new idea for piezocatalytic extraction of uranium.

Designing asymmetrical TMN4 sites via phosphorus or sulfur dual coordination as high-performance electrocatalysts for oxygen evolution reaction

The development ofhighly efficient oxygen evolution reaction (OER) catalysts based on more cost-effective and earth-abundant elements is of great significance and still faces a huge challenge. In this work, a series of transition metal (TM)embedding a newly-defined monolayer carbon nitride phase is theoretically profiled and constructed as a catalytic platform for OER studies. Typically, a four-step screening strategy was proposed to rapidly identified high performance candidates and the coordination structure and catalytic performance relationship was thoroughly analyzed. Moreover, the eliminating criterion was established to condenses valid range based on the Gibbs free energy of OH*. Our results reveal that the as-constructed 2FeCN/P exhibits superior activity toward OER with an ultralow overpotential of 0.25 V, at the same time, the established 3FeCN/S configuration performed well as abifunctional OER/ORR electrocatalysis with extremely low overpotential ηOER/ηORR of 0.26/0.48 V. Overall, this work provides an effective framework for screening advanced OER catalysts, which can also be extended to other complex multistep catalytic reactions.

Potential-dependent activities in interpreting the reaction mechanism of dual-metal atom catalysts for Li-CO2 batteries

CO2 electrochemistry has been considered as a promising cathode reaction for energy storage due to its high theoretical energy density, high electrochemical potential, and ability to fix CO2. However, the low efficiency and poor reversibility of Li-CO2 evolution significantly impede the applications of Li-CO2 batteries. Herein, first-principles calculations were employed to investigate the 21 M1M2N4C dual-atom catalysts and explore the catalytic mechanism for the Li-CO2 evolution reaction. Among these dual-atom catalysts, the MoMoN4C shows the highest adsorption interaction with CO2 due to its high d-center and d-p orbital coupling. The effects of dual-atom sites on the catalytic activities and selectivities were investigated by searching the possible reaction pathways toward the battery-discharging processes in the ether electrolyte with the help of implicit constant electrode potential simulations. The compared results show that the Li-CO2 discharging process was limited by the rate-determining reactions involving *Li + CO2 → *LiCO2 and *LiC2O4@ + Li+ + e- → *CO + Li2CO3, and these processes on graphene are relatively sluggish due to the low onset potential range of -2 to -2.36 V vs. SHE. By contrast, The optimized onset potentials of -1.15 to -1.31 V vs. SHE were obtained at the MoMoN4C active site. Furthermore, the MoMoN4C active site shows a lower energy barrier for the decomposition of *Li2CO3 than the pure graphene, which reveals the MoMoN4C active site with excellent CO2 activation ability can reduce the polarization of the discharging reactions and energy barrier for the CO bond cleavage. This work provides deep insight into the Li-CO2 evolution mechanisms and guides the design of advanced dual-atom catalysts for highly reversible Li-CO2 batteries.

Trigger a multi-electron reaction by tailoring electronic structure of VO2 toward more efficient aqueous zinc metal batteries

VO2 (B) is recognized as a promising cathode material for aqueous zinc metal batteries (AZMBs) owing to its remarkable specific capacity and its unique, expansive tunnel structure, which facilitates the reversible insertion and extraction of Zn2+. Nonetheless, challenges such as the inherent instability of the VO2 structure, poor ion/electron transport and a limited capacity due to the low redox potential of the V3+/V4+ couple have hindered its wider application. In this study, we present a strategy to replace vanadium ions by doping Al3+ in VO2. This approach activates the multi-electron reaction (V4+/V5+), to increase the specific capacity and improve the structural stability by forming robust V5+O and Al3+O bonds. It also induces a local electric field by altering the local electron arrangement, which significantly accelerates the ion/electron transport process. As a result, Al-doped VO2 exhibits superior specific capacity, improved cycling stability, and accelerated electronic transport kinetics compared to undoped VO2. The beneficial effects of heterogeneous atomic doping observed here may provide valuable insights into the improvement electrode materials in metal-ion battery systems other than those based on Zn.

Machine-learning descriptor search on the density of states profile of bimetallic alloy systems and comparison with the d-band center theory

In this study, the electronic density of states (DOSs) calculated with density functional theory (DFT) were analyzed by the machine-learning techniques. More than 400 pure metal and bimetallic alloy systems were calculated with DFT, and obtained the surface DOSs and the CH3 adsorption energy (Ead). By fitting the Gaussian functions to the DOS, multiple descriptors, such as the Gaussian peak positions, heights, and widths were extracted. Several regression methods, such as the least absolute shrinkage of selection operator (LASSO), random-forest, gradient-boosting, and extra-tree were used to find the relationship between these descriptors and the Ead. The results show that the energy position of the peaks in the d-projected DOS is the most important descriptor, in agreement with the previously known d-band center theory. It was also shown that the peak position in d-projected DOS improves the regression model in addition to the d-band center, since it reduces the regression error.

Highly efficient Mn2+, Mg2+, and NH4+ recovery from electrolytic manganese residue via leaching, solvent extraction, coprecipitation, and atmospheric oxidation

Electrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, exhibits substantial leaching toxicity owing to its elevated levels of soluble Mn2+ and NH4+. The leaching and recovery of valuable metal ions and NH4+ from EMR are key to the hazard-free treatment and resource utilization of EMR. In this study, two-stage countercurrent leaching with water was used to leach Mn2+, Mg2+, and NH4+ from EMR. Subsequently, two-stage countercurrent extraction was conducted using α-hydroxy-2-ethylhexyl phosphinic acid (α-H-2-EHA) as an extractant to enrich Mn2+, and Mg2+, and NH4+ were recovered via coprecipitation. Based on the calculations for a single leaching-extraction process, the recoveries of Mn2+, Mg2+, and NH4+ ions exceeded 80%, 99%, and 90%, respectively. In addition, high-purity Mn3O4 with an Mn content of 71.61% and struvite were produced. This process represents a win-win strategy that facilitates the hazard-free treatment of EMR while simultaneously recovering valuable Mn2+, Mg2+, and NH4+ resources from waste. Thus, this study provides a novel approach to the hazard-free and resourceful management of solid waste. ENVIRONMENTAL IMPLICATION: Electrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, poses significant environmental risks due to its soluble heavy metals and ammonia nitrogen content. Efforts have been made to address this issue, but there has been no mature industrial application due to cost or processing capacity constraints. In this work, solvent extraction was first used to enrich Mn2+ from EMR leachate, and a novel α‑hydroxy‑2‑ethylhexyl phosphinic acid was used as extractant. High purity Mn3O4 and struvite was synthesized through this process. The win‑win strategy offers a novel approach for the hazard‑free and resourceful utilization of solid waste.

Silica-supported ionic liquid for efficient gaseous arsenic oxide removal through hydrogen bonding

The emission of highly-toxic gaseous As2O3 (As2O3 (g)) from nonferrous metal smelting poses environmental concerns. In this study, we prepared an adsorbent (SMIL-X) by loading an ionic liquid (IL) ([HOEtMI]NTf2) into MCM-41 through an impregnation-evaporation process and then applied it to adsorb As2O3 (g). SMIL-20% exhibited an As2O3 (g) adsorption capacity of 35.48 mg/g at 400 °C, which was 490% times higher than that of neat MCM-41. Characterization of SMIL-X indicated that the IL was mainly supported on MCM-41 through O-H…O bonds formed between the hydroxyl groups (-OH) and the silanol groups (Si-OH) and the O-H…F bonds formed between the C-F groups and the Si-OH groups. The hydrogen bonds significantly contributed to the adsorption of As2O3 (g), with -NH and -OH groups forming hydrogen bonds with As-O species (i.e., N-H…O and O-H…O). This showed superior performance to traditional adsorbents that rely on van der Waals forces and chemisorption. Moreover, after exposure to high concentrations of SO2, the adsorption capacities remained at 76% of their initial values, demonstrating some sulfur resistance. This study presents an excellent adsorbent for the purification of As2O3 (g) and shows promising application potential for treating flue gas emitted by nonferrous metal smelting processes.

DFT and AIMD insights into heterogeneous dissociation of 2-chlorothiophenol on CuO(111) surface: Impact of H2O and OH

Copper oxides are vital catalysts in facilitating the formation of polychlorinated thianthrenes/dibenzothiophenes (PCTA/DTs) through heterogeneous reactions in high-temperature industrial processes. Chlorothiophenols (CTPs) are the most crucial precursors for PCTA/DT formation. The initial step in this process is the metal-catalyzed production of chlorothiophenoxy radicals (CTPRs) from CTPs via dissociation reactions. This work combines density functional theory (DFT) calculations with ab initio molecular dynamics (AIMD) simulations to explore the formation mechanism of the adsorbed 2-CTPR from 2-CTP, with the assistance of CuO(111). Our study demonstrates that flat adsorption configurations of 2-CTP on the CuO(111) surface are more stable than vertical configurations. The CuO(111) surface acts as a strong catalyst, facilitating the dissociation of 2-CTP into the adsorbed 2-CTPR. Surface oxygen vacancies enhance the adsorption of 2-CTP on the CuO(111) surface, while moderately suppressing the dissociation of 2-CTP. More importantly, water molecules and surface hydroxyl groups actively promote the dissociation of 2-CTP. Specifically, water directly participates in the reaction through "water bridge", enabling a barrier-free process. This research provides molecular-level insights into the heterogeneous generation of dioxins with the catalysis of metal oxides in fly ash from static and dynamic aspects, providing novel approaches for reducing dioxin emissions and establishing dioxin control strategies.

Construction of heterogeneous interfaces for water activation and dissociation to synergistically boost overall water splitting

Construction of heterogeneous interfaces with dual active components to synergistically promote both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an effective strategy for facilitating electrochemical water splitting, but the appropriate active component regulation via simple synthesis procedures is still challenging. Herein, the Co and Co2Mo3O8 active components are screened to construct effective heterogeneous interfaces and successfully integrated on Ni foam by thermal reduction of cobalt molybdate precursor. And this bifunctional electrode (Co/Co2Mo3O8/NF) required overpotentials of only 164 and 360 mV to drive the 100 mA cm-2 for HER and OER in alkaline media, respectively. Theoretical calculations showed that the electron transfer occurred from Co to Co2Mo3O8 at the interface, then the formed interfacial cobalt atoms with deficient electron were beneficial for water activation, and reduced energy barrier of water dissociation under the synergistic effect of Co2Mo3O8. Notably, the alkaline electrolyzer based on symmetric Co/Co2Mo3O8/NF electrodes generated 100 mA cm-2 at a voltage of only 1.75 V, surpassing commercially available precious-metal Pt/RuO2-based catalysts.

Dual-functional ionic liquids additive enables dendrite-free Zn anode with ultra-long cycle life over one year

Zn anodes suffer from the formation of uncontrolled dendrites aggravated by the uneven electric field and the insulating by-product accumulation in aqueous zinc-ion batteries (AZIBs). Here, an effective strategy implemented by 1-butyl-3-methylimidazolium hydrogen sulfate (BMIHSO4) additive is proposed to synergistically tune the crystallographic orientation of zinc deposition and suppress the formation of zinc hydroxide sulfate for enhancing the reversibility on Zn anode surface. As a competing cation, BMI+ is proved to preferably adsorb on Zn-electrode compared with H2O molecules, which shields the "tip effect" and inhibits the Zn-deposition agglomerations to inducing the horizontal growth along Zn (002) crystallographic texture. Simultaneously, the protonated BMIHSO4 additives could remove the detrimental OH- in real-time to fundamentally eliminate the accumulation of 6Zn(OH)2·ZnSO4·4H2O and Zn4SO4(OH)6·H2O on Zn anode surface. Consequently, Zn anode exhibits an ultra-long cycling stability of one year (8762 h) at 0.2 mA cm-2/0.2 mAh cm-2, 3600 h at 2 mA cm-2/2 mAh cm-2 with a high plating cumulative capacity of 3.6 Ah cm-2, and a high average Coulombic efficiency of 99.6 % throughout 1000 cycles. This work of regulating Zn deposition texture combined with eliminating notorious by-products could offer a desirable way for stabilizing the Zn-anode/electrolyte interface in AZIBs.

Tailoring hypervalent Nickel induced by oxygen vacancy toward enhanced oxygen evolution reaction performance in self-supporting NiFe-(oxy)hydroxides electrodes

NiFe-(oxy)hydroxides are the most active transition metal oxide electrocatalysts for oxygen evolution reaction (OER) under the alkaline media. Herein, we controllably manipulated oxygen vacancy (VO)-tunable NiFe-(oxy) hydroxides that their OER performances possessed a volcano-type relationship with VO concentration, positively-correlated with Ni3+/Ni2+ ratio. Theoretical simulations further unearthed the enhanced activation and dissociation of H2O by the inserting of VO. As a result, the optimal sample featuring the Ni3+/Ni2+ ratio of 30.3 % and VO of 23.8 % exhibited the overpotential of 243 mV at the current density of 100 mA cm-2, simultaneously lasting 120 h durability without any attenuation, exceding the most reported NiFe-(oxy)hydroxides. This work offers an innovative view to understand the OER performance using hypervalent Ni ratio induced by VO defects.

Simulation study on functional group-modified Ni-MOF-74 for CH4/N2 adsorption separation

This study employs grand canonical Monte Carlo (GCMC) simulations to investigate the impact of functional group modifications (CH3, OH, NH2, and OLi) on the adsorption performance of CH4/N2 on Ni-MOF-74. The results revealed that functional group modifications significantly increased the adsorption capacity of Ni-MOF-74 for both CH4 and N2. The packed methyl groups in CH3-Ni-MOF-74 create an environment conducive to CH4, leading to the highest CH4 adsorption capacity. The electrostatic potential distribution indicates that the strong electron-donating effect introduced by the alkali metal Li results in the highest electrostatic potential gradient in Li-O-Ni-MOF-74, leading to the strongest adsorption of N2, this is unfavorable for CH4/N2 separation. At 1500 kPa the selectivity order of adsorbents for mixed gases was as follows: CH3-Ni-MOF-74 > NH2-Ni-MOF-74 > OH-Ni-MOF-74 > Ni-MOF-74 > Li-O-Ni-MOF-74. This study highlights that CH3-Ni-MOF-74 possesses optimal CH4 selectivity and adsorption performance. Given the current lack of research on functionalized MOF-74 for the separation of CH4 and N2, the findings of this study will serve as a theoretical guide and provide references for the applications of CH4 adsorption and CH4/N2 separation.

Insight into the effective electrocatalytic sulfide removal from aqueous solutions using surface oxidized stainless-steel anode and its desulfurization mechanism

The electrochemical oxidation of hydrogen sulfide (H2S) has shown its potential for the real application of H2S emission control in wastewater treatment. In this study, a surface corrosion treatment of stainless steel (SS) was optimized by regulate Ni content in the oxide film on the SS AISI 304 surface for sulfide removal. The X-ray photoelectron spectroscopy and linear sweeping voltammetry results indicated a higher Ni content in the oxide film of surface-oxidized stainless steel (SOSS) attributed to a higher sulfide removal potential. Sulfide removal experiment results showed that SS-150 (with 150 s anodic pretreatment) anodes achieved the highest Ni content of 69% with the best sulfide removal efficiency, i.e., 97% within 48 h, which increased by 20% compared to the untreated SS. This study also demonstrated a strategy for in situ removal of deposited sulfur on the anodes by cathodic treatment at -0.38 V vs. RHE to alleviate the common issue of sulfur passivation. Density functional theory (DFT) calculation revealed that NiOOH was the major active species in SS-150 oxide film for a faster sulfide removal rate. The study developed a SS surface modification process for Ni content regulation that contributed to better sulfide removal efficiency.

Heterojunction of MXenes and MN4-graphene: Machine learning to accelerate the design of bifunctional oxygen electrocatalysts

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for the development of excellent bifunctional electrocatalysts, which are key functions in clean energy production. The emphasis of this study lies in the rapid design and investigation of 153 MN4-graphene (Gra)/ MXene (M2NO) electrocatalysts for ORR/OER catalytic activity using machine learning (ML) and density functional theory (DFT). The DFT results indicated that CoN4-Gra/Ti2NO had both good ORR (0.37 V) and OER (0.30 V) overpotentials, while TiN4-Gra/M2NO and MN4-Gra/Cr2NO had high overpotentials. Our research further indicated orbital spin polarization and d-band centers far from the Fermi energy level, affecting the adsorption energy of oxygen-containing intermediates and thus reducing the catalytic activity. The ML results showed that the gradient boosting regression (GBR) model successfully predicted the overpotentials of the monofunctional catalysts RhN4-Gra/Ti2NO (ORR, 0.39 V) and RuN4-Gra/W2NO (OER, 0.45 V) as well as the overpotentials of the bifunctional catalyst RuN4-Gra/W2NO (ORR, 0.39 V; OER, 0.45 V). The symbolic regression (SR) algorithm was used to construct the overpotential descriptors without environmental variable features to accelerate the catalyst screening and shorten the trial-and-error costs from the source, providing a reliable theoretical basis for the experimental synthesis of MXene heterostructures.

Nitroxyl radical triggered the construction of a molecular protective layer for achieving durable Zn metal anodes

The issues of dendrite growth, hydrogen evolution reaction, and zinc anode corrosion have significantly hindered the widespread implementation of aqueous zinc-ion batteries (AZIBs). Herein, trace amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) additive is introduced into AZIBs to protect the zinc metal anode. Trace amounts of the TEMPO additive with nitroxyl radical can provide fast Zn2+ transport and anode protection ability by forming an adsorbed molecular layer via Zn-O bond. This interface not only provides strong interfacial compatibility and promotes dynamic transport of Zn2+, but also induces deposition of Zn2+ along Zn (002) plane. Additionally, the molecular protective layer significantly inhibits hydrogen evolution reaction (HER) and corrosion. The Zn anodes achieve high Coulombic efficiency of up to 99.75 % and long-term plating/stripping of more than 1400 h at 1 mA cm-2 and 0.5 mAh cm-2. The Zn//Zn symmetric cell can operate continuously for 2500 h at a current density of 1 mA cm-2 and 1 mAh cm-2, and it can still last for nearly 1400 h even when the current density is increased to 5 mA cm-2. Furthermore, the Zn//V2O5 full cell using TEMPO/ZnSO4 electrolyte effectively maintains a maximum capacity retention rate of 53.4 % even after 1500 cycles at 5 A/g. This innovative strategy introduces trace additive with free radicals into the electrolyte, which may help to achieve large-scale, ultra-long-life, and low-cost AZIBs.

Co4+ in porous ZIF-67-derives intercalating-bridging adsorption of 2-reaction sites for simultaneous 2-electron transfer toward sensitive detection of uric acid

Metal-organic frameworks (MOFs) have been used to detect uric acid (UA), but still very challenging to achieve a low detection limit due to the low inferior conductivity of MOFs. Herein, three different N-doped ZIF-67-derived carbons were synthesized for the first time by one-step co-pyrolysis of 2-methylimidazole with cobalt nitrate (CN), cobalt acetate (CA) or cobalt chloride (CC) toward UA sensing. Afterwards, the cobalt nitrate-derived Co particle (Co/CN) supported by N-doped ZIF-67-derived carbon displays extremely low detection limit and high sensitivity for UA, outperformed all reported MOFs-based UA sensors. More interestingly, it was discovered that the high valence Co4+ within the Co/CN sample produced in high-acidic environment can intercalate in the frame for a bridge adsorption between two reaction sites, which boosted simultaneous 2-electron transfer, while Co3+ only allows an end-adsorption structure for one-electron transfer being the rate determining step. Furthermore, the bridge adsorption mode of UA on Co4+ -based catalyst was also verified by theoretical DFT calculations and XPS experiment. This work holds great promise for a selective and sensitive UA sensor for practical bioscience and clinic diagnostic applications while shedding lights in fundamental research for innovative designs and developments of high-sensitive electrochemical sensors.

Resolution of the reciprocity between radical species from precursor and closed pore formation in hard carbon for sodium storage

Hard carbon (HC) has emerged as a highly promising anode material for sodium ion batteries, drawing tremendous interest in producing this material with low-cost and easily accessible precursors. The determination of the crucial parameters of precursors influencing the formation of key structures, such as closed pores, in the HC is of paramount importance. Considering the potential role of free radicals in the structural evolution of the precursors, we, for the first time, delve into the impact of radical species on the development of closed pores by electron paramagnetic resonance spectroscopy, with petroleum asphalt as the model system. Our findings reveal that carbon centred radicals, with the g value close to that of the free electron (2.0023), exhibit a propensity to form long-range, well-ordered graphitic structures with lower sodium storage capacity. Conversely, the deliberately incorporated oxygen radicals with the g value over 2.005 require a higher energy for ordering the graphitic structures, leading to the creation of closed pores. As a result, the optimal sample showcases a four-fold increase in plateau capacity for sodium ion storage due to the pore filling process. Our research underscores the pivotal role of employing electron paramagnetic resonance spectroscopy studying the critical structural evolution of functional carbon materials.

NaSn2F5 nanocluster composed of nanoparticles with matched lattices induced by dislocations: Accelerated sodium-ion transport via in situ oxidation in solid-state sodium metal battery

Na metal batteries using inorganic solid-state electrolytes (SSEs) have attracted extensive attention due to their superior safety and high energy density. However, their development is plagued by the unclear structural/volumetric evolution of SSEs and the corresponding Na+ migration mechanisms. In this work, NaSn2F5 (NSF) clusters are composed of nanoparticles (NPs) with matched lattices induced by dislocations, which can mitigate the volume swelling/shrinkage of the NPs. NSF behaves like a single ion conductor with a high Na+ transference number (tNa+) of 0.79. Specially, the ionic conductivity (σ) of NSF is increased from 7.64 × 10-6 to 5.42 × 10-5 S cm-1 after partial irreversible oxidation of Sn2+ (0.118 Å) → Sn4+ (0.069 Å) with the shrunk ionic radius during the charge process, giving more spaces for Na+ migration. Furthermore, a poly(acrylonitrile)-NaSn2F5-NaPF6 composite polymer electrolyte (NSF CPE) was fabricated with a σ of 4.13 × 10-4 S cm-1 and a tNa+ of 0.60. The NSF CPE-based symmetric cell can operate over 3000 h due to the couplings between the different components in NSF CPE, which is beneficial for ion transfer and the construction of stable solid electrolyte interface. And the quasi-solid-state Na|NSF CPE|Na3V2(PO4)3 full cell displays excellent electrochemical performance.

Rational design of covalent organic frameworks/NaTaO3 S-scheme heterostructure for enhanced photocatalytic hydrogen evolution

As a typical perovskite material, NaTaO3 has been regarded as a potential catalyst for photocatalytic hydrogen evolution (PHE) process, due to its excellent photoelectric property and superior chemical stability. However, the photocatalytic activity of pure NaTaO3 was largely restricted by its poor visible-light absorption ability and rapid recombination of photogenerated charge carriers. Therefore, a covalently bonded TpBpy covalent organic framework (COF)/NaTaO3 (TpBpy/NaTaO3) heterostructure was designed and synthesized by the post modification strategy with (3-aminopropyl) triethoxysilane (APTES) and the in situ solvothermal process. Benefiting from the enhanced built-in electric field by the interfacial covalent bonds and the formation of S-scheme heterostructure between TpBpy and NaTaO3, which were proved by the Ar+-cluster depth profile and X-ray photoelectron spectroscopy (XPS), as well as density functional theory (DFT) calculation results, both the charge transfer efficiency and the PHE performance of the TpBpy/NaTaO3 composites were significantly improved. Additionally, the composites exhibited an excellent absorption performance in the visible region, which was also beneficial for the photocatalytic process. As expected, the optimal TpBpy/20%NaTaO3 composite achieved a remarkable hydrogen evolution rate of 17.3 mmol·g-1·h-1 (10 mg of catalyst) under simulated sunlight irradiation, which was about 173 and 2.4 times higher than that of pure NaTaO3 and TpBpy, respectively. This work provided a novel strategy for constructing highly effective and stable semiconductor/COFs heterostructures with strong interfacial interaction for photocatalytic hydrogen evolution.

Effective nitrogen doping of TiO2 polymorphs at mild temperatures for visible-light-responsive hydrogen evolution

Herein, a mild-temperature nitrogen doping route with the urea-derived gaseous species as the active doping agent is proposed to realize visible-light-responsive photocatalytic hydrogen evolution both for the anatase and rutile TiO2. DFT simulations reveal that the cyanic acid (HOCN), derived from the decomposition of urea, plays a curial role in the effective doping of nitrogen in TiO2 at mild temperatures. Photocatalytic performance demonstrates that both the anatase and rutile TiO2 doped at mild temperatures exhibit the highest hydrogen evolution rates, although the ones prepared at high temperatures possess higher absorbance in the visible range. Steady-state and transient surface photovoltage characterizations of these doped TiO2 polymorphs prepared at different temperatures reveal that harsh conditions (high temperature reaction) typically result in the formation of intrinsic defects that are detrimental to the transport of the low-energy visible-light-induced electrons, while the mild-temperature nitrogen-doping could flatten the pristine upward band bending without triggering the formation of Ti3+, thus achieving enhanced visible-light-responsive hydrogen evolution rates. We anticipate that our findings will provide inspiring information for shrinking the gap between the visible-light-absorbance and the visible-light-responsiveness in the band engineering of wide-bandgap metal-oxide photocatalysts.

Revealing the Influence of Electron Migration Inside Polymer Electrolyte on Li+ Transport and Interphase Reconfiguration for Li Metal Batteries

The development of highly producible and interfacial compatible in situ polymerized electrolytes for solid-state lithium metal batteries (SSLMBs) have been plagued by insufficient transport kinetics and uncontrollable dendrite propagation. Herein, we seek to explore a rationally designed nanofiber architecture to balance all the criteria of SSLMBs, in which La0.6Sr0.4CoO3-δ (LSC) enriched with high valence-state Co species and oxygen vacancies is developed as electronically conductive nanofillers embedded within ZnO/Zn3N2-functionalized polyimide (Zn-PI) nanofiber framework for the first time, to establish Li+ transport highways for poly vinylene carbonate (PVC) electrolyte and eliminate nonuniform Li deposits. Revealed by characterization and theoretical calculation under electric field, the positive-negative electrical dipole layer in LSC derived from electron migration between Co and O atoms aids in accelerating Li+ diffusion kinetics through densified electric field around filler particle, featuring a remarkable ionic conductivity of 1.50 mS cm-1 at 25 °C and a high Li+ transference number of 0.91 without the risk of electron leakage. Integrating with the preferential sacrifice of ZnO/Zn3N2 on PI nanofiber upon immediate detection of dendritic Li, which takes part in reconfiguring hierarchical SEI chemistry dominated by LixNy/Li-Zn alloy inner layer and LiF outer layer, SSLMBs are further endowed with prolonged cycling lifespan and exceptional rate capability.

Nuclear quantum effects in phase transition between Ice VII and Ice X

The theoretical modeling of high-pressure ice remains challenging owing to the complexity in accurately reflecting its properties attributable to nuclear quantum effects. To explore the nuclear quantum effects of the phase transition between Ice VII and Ice X, we introduce an approach based on ab initio path-integral molecular dynamics. The results indicate that quantum effects facilitate the phase transition, with the observed isotope effects consistent with the experimental outcomes. We demonstrate that quantum effects manifest differently across ice phases: In Ice VII, quantum effects reduce the pressure through the centralization of protons. In contrast, in Ice X, quantum effects increase the pressure owing to the increased kinetic energy of zero-point vibration.

The Impact of Electron Donating and Withdrawing Groups on Electrochemical Hydrogenolysis and Hydrogenation of Carbonyl Compounds

The hydrogenolysis or hydrodeoxygenation of a carbonyl group, where the C═O group is converted to a CH2 group, is of significant interest in a variety of fields. A challenge in electrochemically achieving hydrogenolysis of a carbonyl group with high selectivity is that electrochemical hydrogenation of a carbonyl group, which converts the C═O group to an alcohol group (CH-OH), is demonstrated not to be the initial step of hydrogenolysis. Instead, hydrogenation and hydrogenolysis occur in parallel, and they are competing reactions. This means that although both hydrogenolysis and hydrogenation require adding H atoms to the carbonyl group, they involve different intermediates formed on the electrode surface. Thus, revealing the difference in intermediates, transition states, and kinetic barriers for hydrogenolysis and hydrogenation pathways is the key to understanding and controlling hydrogenolysis/hydrogenation selectivity of carbonyl compounds. In this study, we aimed to identify features of reactant molecules that can affect their hydrogenolysis/hydrogenation selectivity on a Zn electrode that was previously shown to promote hydrogenolysis over hydrogenation. In particular, we examined the electrochemical reduction of para-substituted benzaldehyde compounds with substituent groups having different electron donating/withdrawing abilities. Our results show a strikingly systematic impact of the substituent group where a stronger electron-donating group promotes hydrogenolysis and a stronger electron-withdrawing group promotes hydrogenation. These experimental results are presented with computational results explaining the substituent effects on the thermodynamics and kinetics of electrochemical hydrogenolysis and hydrogenation pathways, which also provide critically needed information and insights into the transition states involved with these pathways.

First-principles study on structural stabilities, mechanical properties, and biaxial strain-induced superconductivity in Janus MoWC monolayer

The unique attributes of hydrophilicity, expansive surface groups, remarkable flexibility, and superior conductivity converge in MXene, a pioneering 2D material. Owing to MXene's exceptional properties, diverse strategies have been explored to enhance its characteristics. Janus MXene and stress-strain response considerations represent the primary avenues of interest today. In this study, we investigated the Janus MXene structure under biaxial stress using first-principles calculations. The most stable configuration of Janus MoWC MXene identified in our analysis exhibits an atomic arrangement known as the hexagonal (2H) phase. Subsequently, we examined the mechanical and electronic properties of 2H-MoWC when subjected to biaxial strain. Our findings indicate that the 2H phase of Janus MoWC MXene demonstrates superior strength compared to the tetragonal (1T) phase. Analysis of the ELF of the 2H-MoWC structure unveiled that the robust C-C bond within the material is the underlying factor enabling the 2H phase to withstand a maximum of 9% tensile strain. Furthermore, we demonstrate that 2H-MoWC is a superconductor with the superconducting temperature (Tc) of 1.6 K, and the superconductivity of 2H phase can be enhanced by biaxial strain with the Tc reaching 7 K. This study offers comprehensive insights into the properties of Janus MoWC monolayer under biaxial stress, positioning it as a promising candidate for 2D straintronic applications.

Hybridization State Transition under Working Conditions: Activity Origin of Single-Atom Catalysts

Single-atom catalysts (SACs) have been widely investigated and have emerged as a transformative approach in electrocatalysis. Despite their clear structure, the origin of their exceptional activity remains elusive. Herein, we elucidate a common phenomenon of the hybridization state transition of metal centers, which is responsible for the activity origin across various SACs for different reactions. Focusing on N-doped carbon-supported Ni SAC (NiN4 SAC) for CO2 reduction reaction (CO2RR), our comprehensive computations successfully clarify the hybridization state transition under working conditions and its relation with the activity. This transition, triggered by the reaction intermediates and applied potential, converts the Ni center from the inert dsp2 hybridization state to the active d2sp3 hybridization state. Importantly, the calculated activity and selectivity of the CO2RR over the d2sp3-hybridized Ni center are consistent with the experimental results, offering strong support for the proposed hypothesis. This work suggests a universal principle of electronic structure evolution in SACs that could revolutionize catalyst design, which also introduces a new paradigm for manipulating electronic states to enhance catalytic performance, with implications for various reactions and catalyst platforms.

Competing Charge Transfer and Screening Effects in Two-Dimensional Ferroelectric Capacitors

Two-dimensional (2D) ferroelectrics promise ultrathin flexible nanoelectronics, typically utilizing a metal-ferroelectric-metal sandwich structure. Electrodes can either contribute free carriers to screen the depolarization field, enhancing nanoscale ferroelectricity, or induce charge doping, disrupting the long-range crystalline order. We explore electrodes' dual roles in 2D ferroelectric capacitors, supported by first-principles calculations covering a range of electrode work functions. Our results reveal volcano-type relationships between ferroelectric-electrode binding affinity and work function, which are further unified by a quadratic scaling between the binding energy and the transferred interfacial charge. At the monolayer limit, charge transfer dictates the ferroelectric stability and switching properties. This general characteristic is confirmed in various 2D ferroelectrics including α-In2Se3, CuInP2S6, and SnTe. As the ferroelectric layer's thickness increases, the capacitor stability evolves from a charge-transfer-dominated state to a screening-dominated state. The delicate interplay between these two effects has important implications for 2D ferroelectric capacitor applications.

Spectrum-Dependent Image Convolutional Processing via a Two-Dimensional Polarization-Sensitive Photodetector

Currently, the improvement in the processing capacity of traditional processors considerably lags behind the demands of real-time image processing caused by the advancement of photodetectors and the widespread deployment of high-definition image sensors. Therefore, achieving real-time image processing at the sensor level has become a prominent research domain in the field of photodetector technology. This goal underscores the need for photodetectors with enhanced multifunctional integration capabilities than can perform real-time computations using optical or electrical signals. In this study, we employ an innovative p-type semiconductor GaTe0.5Se0.5 to construct a polarization-sensitive wide-spectral photodetector. Leveraging the wide-spectral photoresponse, we realize three-band imaging within a wavelength range of 390-810 nm. Furthermore, real-time image convolutional processing is enabled by configuring appropriate convolution kernels based on the polarization-sensitive photocurrents. The innovative design of the polarization-sensitive wide-spectral GaTe0.5Se0.5-based photodetector represents a notable contribution to the domain of real-time image perception and processing.

Ultrastrong Coupling between Polar Distortion and Optical Properties in Ferroelectric MoBr2O2

Tuning the properties of materials by using external stimuli is crucial for developing versatile smart materials. Strong coupling among the order parameters within a single-phase material constitutes a potent foundation for achieving precise property control. However, cross-coupling is fairly weak in most single materials. Leveraging first-principles calculations, we demonstrate a layered mixed anion compound MoBr2O2 that exhibits electric-field switchable spontaneous polarization and ultrastrong coupling between polar distortion and electronic structures as well as optical properties. It offers feasible avenues of achieving tunable Rashba spin-splitting, electrochromism, thermochromism, photochromism, and nonlinear optics by applying an external electric field to a single domain sample and heating, as well as intense light illumination. Additionally, it exhibits an exceptionally large photostrictive effect. These findings not only showcase the feasibility of achieving multiple order parameter coupling within a single material but also pave the way for comprehensive applications based on property control, such as energy harvesting, information processing, and ultrafast control.

Constructing Tunable Electrides on Monolayer Transition Metal Dichalcogenides

Electrides have emerged as promising materials with exotic properties due to the presence of localized electrons detached from all atoms. Despite the continuous discovery of many new electrides, most of them are based on atypical compositions, and their applications require an inert surface structure to passivate reactive excess electrons. Here, we demonstrate a different route to attain tunable electrides. We first report that monolayer transition metal dichalcogenides (TMDCs) exhibit weak electride characteristics, which is the remainder of the electride feature of the transition metal sublattice. By introducing chalcogen vacancies, the enhanced electride characteristics are comparable to those of known electrides. Since the precise tailoring of the chalcogen vacancy concentration has been achieved experimentally, we proposed that TMDCs can be used to build electrides with controllable intensities. Furthermore, we demonstrate that the electride states at the chalcogen vacancy of monolayer TMDCs will play an important role in catalyzing hydrogen evolution reactions.

Synthesis and symmetry of perovskite oxynitride CaW(O,N)3

Perovskite oxynitrides, in addition to being promising electrocatalysts and photoabsorbers, present an interesting case study in crystal symmetry. Full or partial ordering of the O and N anions affects global symmetry and influences material performance and functionality; however, anion ordering is challenging to detect experimentally. In this work, we synthesize a novel perovskite oxynitride CaW(O,N)3 and characterize its crystal structure using both X-ray and neutron diffraction. Through co-refinement of the diffraction patterns with a range of literature and theory-derived model structures, we demonstrate that CaW(O,N)3 adopts an orthorhombic Pnma average structure and exhibits octahedral distortion with evidence for preferred anion site occupancy. However, through comparison with a large, low-symmetry unit cell, we identify the presence of disorder that is not fully accounted for by the high-symmetry model. We compare CaW(O,N)3 with SrW(O,N)3 to demonstrate the broader presence of such disorder and identify contrasting features in the electronic structures. This work signifies an updated perspective on the inherent crystal symmetry present in perovskite oxynitrides.

Coupling High Hardness and Zn Affinity in Amorphous-Crystalline Diamond for Stable Zn Metal Anodes

The highly reversible plating/stripping of Zn is plagued by dendrite growth and side reactions on metallic Zn anodes, retarding the commercial application of aqueous Zn-ion batteries. Herein, a distinctive nano dual-phase diamond (NDPD) comprised of an amorphous-crystalline heterostructure is developed to regulate Zn deposition and mechanically block dendrite growth. The rich amorphous-crystalline heterointerfaces in the NDPD endow modified Zn anodes with enhanced Zn affinity and result in homogeneous nucleation. In addition, the unparalleled hardness of the NDPD effectively overcomes the high growth stress of dendrites and mechanically impedes their proliferation. Moreover, the hydrophobic surfaces of the NDPD facilitate the desolvation of hydrate Zn2+ and prevent water-mediated side reactions. Consequently, the Zn@NDPD presents an ultrastable lifespan exceeding 3200 h at 5 mA cm-2 and 1 mAh cm-2. The practical application potential of Zn@NDPD is further demonstrated in full cells. This work exhibits the great significance of a chemical-mechanical synergistic anode modification strategy in constructing high-performance aqueous Zn-ion batteries.

The past 10 years of molecular ferroelectrics: structures, design, and properties

Ferroelectricity, which has diverse important applications such as memory elements, capacitors, and sensors, was first discovered in a molecular compound, Rochelle salt, in 1920 by Valasek. Owing to their superiorities of lightweight, biocompatibility, structural tunability, mechanical flexibility, etc., the past decade has witnessed the renaissance of molecular ferroelectrics as promising complementary materials to commercial inorganic ferroelectrics. Thus, on the 100th anniversary of ferroelectricity, it is an opportune time to look into the future, specifically into how to push the boundaries of material design in molecular ferroelectric systems and finally overcome the hurdles to their commercialization. Herein, we present a comprehensive and accessible review of the appealing development of molecular ferroelectrics over the past 10 years, with an emphasis on their structural diversity, chemical design, exceptional properties, and potential applications. We believe that it will inspire intense, combined research efforts to enrich the family of high-performance molecular ferroelectrics and attract widespread interest from physicists and chemists to better understand the structure-function relationships governing improved applied functional device engineering.