Theoretical surface science and catalysis—calculations and concepts

Construction of Ni2P/WS2/CoWO4@C multi-heterojunction electrocatalysis derived from heterometallic clusters for superior overall water splitting

The reasonable design of an economical and robust bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is both essential but challenging. Herein, we synthesized a multi-interfacial Ni2P/WS2/CoWO4@C hybrid electrocatalyst devived from the heterometallic clusters [Co24(TC4A)6(WO4)8Cl6][HPW12O40], in which Ni2P was incorporated into WS2/CoWO4@C nanosheets via interfacial interactions by in situ phosphorization processes. Theoretical calculations revealed that moderate electron transfer from CoWO4 and Ni2P to WS2 induced by the multi-heterojunction significantly regulate the binding energies of the reactive intermediates, thus enhacing its intrinsic activity. Under alkaline medium, the overpotential of the optimized Ni2P/WS2/CoWO4@C electrocatalyst for OER and HER is only 206 mV and 90 mV at 10 mA cm-2, respectively, with extraordinary stability more than 100 h, and the potential of overall water splitting is only 1.46 V. This work motivates further research and presents a reliable design route for other heterojunction engineered cost-effective bifuctional electrocatalysts.

Inverted Trends of the Brønsted-Evans-Polanyi Relation in N2 Dissociation Originated from a Bonding-Dependent Adsorption Mechanism

The search for efficient Haber-Bosch catalysts toward ammonia production under mild conditions is never-ending, which is greatly limited by the Brønsted-Evans-Polanyi (BEP) relationship. Great efforts have been put into optimizing the BEP relations and achieving the Sabatier optimum, which requires a balance between the dissociation and hydrogenation of nitrogen. However, challenges in this field inspire us to believe that completely breaking the linear BEP relations is indeed the final target although out of sight in such a holy grail reaction. Here, based on the first-principles calculations, we discover inverted trends of BEP relation of N2 dissociation to approach the kinetic optimum of ammonia synthesis on Fe-based single-atom alloys. It is found that the adsorption characteristic of N-N transition states follows the 10-electron count rule, while that of the final states mimics the d-band model, which accounts for the inversion. Crystal orbital Hamiltonian populations (COHP) and Bader charge analysis further corroborate that a bonding-dependent adsorption mechanism lies at the root of the inverted trends of the BEP relation. Our finding not only paves the way for the milder Haber-Bosch process but also promotes explorations of breaking the linear BEP relations of the critical steps in various chemical reactions.

Hemilabile Coordination in Single-Atom Catalyst: A Strategy To Overcome the Limitation of the Scaling Relationship

Traditional catalyst optimization, based on the Sabatier principle, encounters performance limits due to the scaling relationship between binding energies for a series of adsorbates. This restriction prevents independent optimization of the reactant activation and product desorption. Single-atom catalysts (SACs) offer a unique advantage, with their ability to dynamically adjust the metal-support coordination environment. This flexibility allows us to apply hemilability, a concept from homogeneous catalysis, to modulate catalytic activity. Hemilability, which involves the reversible opening and closing of the coordination site, enables SACs to dynamically alter their electronic structure, effectively decoupling the competing requirements of activation and desorption. In this Perspective, we highlight how SACs, with hemilabile metal-support coordination, represent a promising strategy to bypass the limitations imposed by the scaling relationship. We also discuss the experimental challenges and future opportunities for directly observing and controlling these dynamic processes in SACs, thus presenting a powerful way for developing more efficient catalytic systems.

Role of Water in Green Carbon Science

Within the context of green chemistry, the concept of green carbon science emphasizes carbon balance and recycling to address the challenge of achieving carbon neutrality. The fundamental processes in this field are oxidation and reduction, which often involve simple molecules such as CO2, CO, CH4, CHx, and H2O. Water plays a critical role in nearly all oxidation-reduction processes, and thus, it is a central focus of research in green carbon science. Water can act as a direct source of dihydrogen in reduction reactions or participate in oxidation reactions, frequently involving O-O coupling to produce hydrogen peroxide or dioxygen. At the atomic level, this coupling involves the statistically unfavorable proximity of two atoms, requiring optimization through a catalytic process influenced by two types of factors, as described by the authors. Extrinsic factors are related to geometrical and electronic criteria associated with the catalytic metal, involving its d-orbitals (or bands in the case of zerovalent metals and electrodes). Intrinsic factors are related to the coupling of oxygen atoms via their p-orbitals. At the mesoscopic or microscopic scale, the reaction medium typically consists of mixtures of lipophilic and hydrophilic phases with water, which may exist under supercritical conditions or as suspensions of microdroplets. These reactions predominantly occur at phase interfaces. A comprehensive understanding of the phenomena across these scales could facilitate improvements and even lead to the development of novel conversion processes.

Advancing CO2 Conversion with Cu-LDHs: A Review of Computational and Experimental Studies

Layered Double Hydroxides (LDHs) are versatile materials with tuneable properties. They show promising electro- and photo-catalytic activity in the activation and conversion of CO2. Their unique properties make LDHs pivotal materials in emerging sustainable strategies for mitigating the effect of CO2 emissions. However, the intricate structure-property relationship inherent to LDHs challenges their rational design. In this review, we provide a comprehensive overview of both experimental and computational studies about LDHs for photo- and electro-catalytic conversion of CO2, mainly focusing on Cu-based systems due to their superior performance in producing C2 products. We present a background framework, describing the essentials computational and experimental tools, designed to support both experimentalists and theoreticians in the development of tailored LDH materials for efficient and sustainable CO2 valorisation. Finally, we discuss future potential advancements, emphasizing the importance of new synergistic experimental-computational studies.

The Roles of Surface Hydrogen and Hydroxyl in Alkaline Hydrogen Oxidation on Ni-Based Electrocatalysts

One important target for anion exchange membrane fuel cells (AEMFCs) is to enable the application of anode non-precious metal hydrogen oxidation reaction (HOR) catalyst. Nickel presents a promising candidate for alkaline HOR; yet, its practical application is hampered by the intrinsically sluggish activity and poor stability. Herein, a series of Ni-based metals (Ni5Mo, Ni25Co, Ni14W and Ni) are electrodeposited as model catalysts to systematically explore the alkaline HOR by considering the role of adsorbed hydroxyl (OHad). Spectroscopic studies together with density functional theory calculations shed light on the beneficial effect of transition metal M (M=Mo, Co, W) alloying/doping on HOR by introducing the charge transfer from M to Ni and down shifting Ni 3d band center. The HOR specific activities on Ni-based catalysts reveal a volcano-type relationship with the hydrogen binding energy (HBE). The strongly adsorbed OHad is proven to induce deactivation for Ni active sites, and the deactivation potential is OHad binding energy (OHBE) dependent. This study adds new insight into the HOR mechanism and stability of Ni-based electrocatalysts, providing a new avenue for the rational design of highly efficient and robust alkaline HOR catalysts.

Ultrafast Carbothermal Shock Synthesis of Intermetallic Silicides with Anion-Cation Double Active Sites for Efficient Hydrogen Evolution

The exploration and elucidation of the active site of catalysts is crucial for advancing the comprehension of the catalytic mechanism and propelling the development of exceptional catalysts. Herein, it is unveiled that anionic Si and cationic Pt in platinum silicide (PtSi) intermetallic compounds, obtained by ultrafast Joule heating (PtSi JH), simultaneously function as dual active sites for the hydrogen evolution reaction (HER). Density functional theory calculations reveal that, when both Pt and Si simultaneously serve as the active sites, the Gibbs free energy of hydrogen adsorption is 0.70 eV, significantly lower than that of either Pt (1.14 eV) or Si (0.90 eV) alone. Furthermore, both Pt-H and Si-H species are monitored by in situ Raman during the HER process. Consequently, PtSi JH exhibits ultralow overpotentials of 14, 30, and 51 mV at current densities of 10, 50, and 100 mA cm-2, respectively, outperorming commercial Pt/C and Si powder. More importantly, the Joule heating method represents a versatile approach for synthesizing a range of metal silicides including RhSi, RuSix, and Pd2Si. Therefore, this work opens a new avenue for the identification of genuine active sites and explores promising metal silicide for HER electrocatalysis and beyond.

Trimodal Hierarchical Porous Carbon Nanoplates with Edge Curvature for Faster Mass Transfer and Enhanced Oxygen Reduction

Although hierarchical porous carbon materials have been widely used for electrocatalysis, the role of curvature in carbon nanostructures during electrochemical reactions remains poorly understood due to a lack of experimental models featuring clearly defined curved geometries and periodic structures. In this study, we fabricate hierarchical porous cobalt- and nitrogen-containing carbon nanoplates with trimodal porosity (macro-, meso-, and micropores) and continuous, homogeneous curved edges (Co/N-CNP-CURV) using a polystyrene-directed templating approach. The Co/N-CNP-CURV catalyst exhibits excellent catalytic activity and stability for the alkaline oxygen reduction reaction, with a half-wave potential of 0.82 V and a minimal potential shift of 8 mV after 5000 cycles. The enhanced electrocatalytic activity is attributed to synergistic combinations of the trimodal porosity, abundant Co-Nx active sites, a high density of curved edges, and graphitic carbon encapsulated with cobalt nanoparticles. Density functional theory calculations reveal that the presence of curvature in Co/N-CNP-CURV is beneficial for enhancing the charge transfer from the catalyst to O2, lowering the adsorption energy of O2, and reducing the activation free energy barrier for the rate-determining step (*O2 + (H+ + e-) → *OOH). The study provides compelling experimental evidence supporting the critical role of the curvature effect in enhancing the electrocatalytic performance of nanoporous metal-containing carbon materials.

Heterostructured Electrocatalysts: from Fundamental Microkinetic Model to Electron Configuration and Interfacial Reactive Microenvironment

Electrocatalysts can efficiently convert earth-abundant simple molecules into high-value-added products. In this context, heterostructures, which are largely determined by the interface, have emerged as a pivotal architecture for enhancing the activity of electrocatalysts. In this review, the atomistic understanding of heterostructured electrocatalysts is considered, focusing on the reaction kinetic rate and electron configuration, gained from both empirical studies and theoretical models. We start from the fundamentals of the microkinetic model, adsorption energy theory, and electric double layer model. The importance of heterostructures to accelerate electrochemical processes via modulating electron configuration and interfacial reactive microenvironment is highlighted, by considering rectification, space charge region, built-in electric field, synergistic interactions, lattice strain, and geometric effect. We conclude this review by summarizing the challenges and perspectives in the field of heterostructured electrocatalysts, such as the determination of transition state energy, their dynamic evolution, refinement of the theoretical approaches, and the use of machine learning.

Design a Functional Graphene with Decoration of Dual Transition Metal Dopants for Hydrogen Evolution Electrocatalysis

Since hydrogen is a promising alternative to fossil fuels due to its high energy density and environmental friendliness, water electrolysis for hydrogen production has received widespread attentions wherein the development of active and stable catalytic materials is a key research direction. This article designs a dual transition metal doped functional graphene for hydrogen evolution reaction via density functional theory calculations. Among varied combinations, 16 candidates are screened out that are expected to be stable as reflected by the criterion of formation energy Ef<0 and active due to its free energy of hydrogen adsorption ▵GH within the window of ±0.3 eV. Considering its feasibility in structural modification and electronic adjustment due to the strong dd orbital couplings, the homogeneous dual-atom moiety delivers improved performance toward hydrogen evolution in comparison with the single-atom counterpart. Owing to the good resistance of electrochemical dissolution, the work figures out the potential combinations of Cu2C3N3, Rh2C6, Rh2C3N3 and Rh2N6 endowed with the ▵GH values of -0.03, 0.12, -0.21, and 0.06 eV, respectively, being comparable to the benchmark Pt materials. Therefore, this study provides a new direction for the experimental synthesis of highly active carbon-based electrocatalysts and highlights the well-tuning ability posed by the dual-atom interaction.

Microkinetic Modelling of Electrochemical Oxygen Evolution Reaction on Ir(111)@N-Graphene Surface

We have explored the thermodynamics and microkinetic aspects of oxygen evolution catalysis on low loading of Ir(111) on nitrogen-doped graphene at constant potential. The electronic modification induced by N-doping is the reason for the reduced overpotential of OER. The N-induced defect in the charge density is observed with increasing charge-depleted region around the Ir atoms. The lattice contraction shifts the d-band center away from the Fermi level, which increases the barrier for OH* and O* formation on Ir(111) supported on NGr (Ir(111)@NGr). Thus, highly endothermic O* formation reduces the OOH* formation, which is the potential determining step. For comparison, all electronic and binding energy calculations were also performed against Ir NP supported on Gr (Ir(111)@Gr). The stepwise potential-dependent activation barrier (G a ${{G}_{a}}$ ) was obtained using the charge extrapolation method. The third step remains the RDS in all ranges of water oxidation potentials. The potential dependentG a ${{G}_{a}}$ is further applied to the Eyring rate equation to obtain the current density (j O E R ${{j}_{OER}}$ ) and correlation betweenj O E R ${{j}_{OER}}$ and pH dependence, i. e., OH- concentration. The microkineticj O E R ${{j}_{OER}}$ progression leads to a Tafel slope value of 30 mV dec-1 at pH=14.0, requiringη k i n e t i c = 0 . 33 V ${{\eta }_{kinetic}=0.33\ V}$ .

Colloidal High Entropy Alloy Nanoparticles: Synthetic Strategies and Electrocatalytic Properties

High entropy alloy (HEA) nanoparticles (NPs) have attracted much attention recently due to their unprecedented chemical properties. As such, HEA NPs have been used as materials with superior activity toward electrocatalytic applications. Specifically, solid solutions that form randomly mixed single-phased structures have received the most focus in the early stages of HEA NP development for their entropic-driven design and multifunctionality. Advances to non-colloidal and colloidal synthetic methods have allowed for the fabrication of solid solution HEA NPs with varying compositions and complexity to be applied to many practical applications such as fuel cells, energy storage and agriculture. In this review, the current colloidal methods and catalytic mechanisms for solid solution HEA NP synthesis are investigated from the physical chemistry perspective. A comprehensive discussion on the theory, techniques, and electrocatalytic applications of colloidal syntheses for successful solid solution HEA NP formation is presented. Finally, promising perspectives for the continued development of physical insights into structure-property relationships towards improved HEA NP synthesis and application are discussed.

Tuning of Zr content in TiMn2 based multinary alloys by powder metallurgy to fabricate superior hydrogen storage properties

TiMn2 based multinary alloys make full use of the high abundance of rare earth resources in attractive applications of hydrogen storage but suffer from mediocre hydrogen ab/desorption kinetics and lack the in-depth mechanism analysis of hydrogenation/dehydrogenation behavior. Herein, on the basis of current research on compositional modulation, we utilize the low-cost powder metallurgy method to prepare Ti0.9+xZr0.1-xMn1.4Cr0.4V0.2 (x = -0.05, 0, 0.05) hydrogen storage alloy powders, which effectively reduces the preparation cost. What's more, the fractional substitution of Zr for Ti boosts the hydrogenation by introducing defects and modulating the d-band center. The synthesized Ti0.85Zr0.15Mn1.4Cr0.4V0.2 hydrogen storage sample manifests exceptional hydrogen kinetics (almost no incubation) and hydrogen storage capacity (1.73 wt%). The intrinsic reaction mechanism of Zr substitution is elucidated from the viewpoint of microstructure and strain engineering, combined with density functional theory (DFT) analysis. This study provides valuable insights into the design and application of high-performance TiMn2 based multinary hydrogen storage alloys.

Controlling electrocatalytic nitrate reduction efficiency by utilizing dπ-pπ interactions in parallel stacking molecular systems

Electrochemical reduction of nitrate to ammonia using electrocatalysts is a promising alternative strategy for both wastewater treatment and production of green ammonia. Numerous tactics have been developed to increase the electrocatalyst's NO3RR activity. Herein, we report a unique molecular alignment-dependent NO3RR performance using α-CuPc and β-CuPc nanostructures as effective electrocatalysts for the ambient synthesis of ammonia. The well-aligned β-CuPc demonstrated an impressive ammonia yield rate of 62 703 μg h-1 mgcat -1 and a Faradaic efficiency of 96%. In contrast, the less well-aligned α-CuPc exhibited a yield rate of 36 889 μg h-1 mgcat -1 and a Faradaic efficiency of 61% at -1.1 V vs. RHE under the same conditions. Scanning tunneling microscopy/spectroscopy (STM/S) confirms that the well-aligned β-CuPc exhibits superior transport properties due to optimal interaction of the Cu atom with the nitrogen atom of parallel molecules (dπ-pπ) in its one-dimensional nanostructure, which is clearly reflected in the electrocatalytic performance. Furthermore, theoretical research reveals that the NO3RR is the predominant process on the β-CuPc catalyst in comparison to the hydrogen evolution reaction, which is verified by gas chromatography, with β-CuPc exhibiting weaker binding of the *NO intermediate at the copper site and a lower overpotential, hence facilitating the NO3RR relative to α-CuPc.

Theoretical understanding and prediction of metal-doped CeO2 catalysts for ammonia dissociation

Ammonia plays a critical role in energy and environmental catalysis, particularly in ammonia dissociation reactions. Understanding the adsorption and dissociation of ammonia-related species on catalysts is essential for the development of new chemical reactions and high-performance catalysts. However, establishing the relationship between catalyst properties and the adsorption of dissociated species remains challenging, particularly for metal oxide catalysts. This study employs density functional theory calculations to investigate the adsorption properties of ammonia and dissociated intermediate species on metal-doped CeO2. Through a feature correlation heat map, certain descriptors, such as single atom formation energy, gaseous atom formation heat, valence band maximum, and work function, were determined to exhibit a strong linear relationship with the adsorption properties of NHx species. As deduced from the density of states properties and orbital theory, it is also found that the energy difference between the lowest unoccupied orbital of the metal and the highest occupied orbital of ammonia, has a good relationship with the adsorption energy of NH3.

Operando-informed precatalyst programming towards reliable high-current-density electrolysis

Electrocatalysts support crucial industrial processes and emerging decarbonization technologies, but their design is hindered by structural and compositional changes during operation, especially at application-relevant current densities. Here we use operando X-ray spectroscopy and modelling to track, and eventually direct, the reconstruction of iron sulfides and oxides for the oxygen evolution reaction. We show that inappropriate activation protocols lead to uncontrollable Fe oxidation and irreversible catalyst degradation, compromising stability and reliability and precluding predictive design. Based on these, we develop activation programming strategies that, considering the thermodynamics and kinetics of surface reconstruction, offer control over precatalyst oxidation. This enables reliable predictions and the design of active and stable electrocatalysts. In a NixFe1-xS2 model system, this leads to a threefold improvement in durability after programmed activation, with a cell degradation rate of 0.12 mV h-1 over 550 h (standard operation: 0.29 mV h-1, constrained to 200 h), in an anion exchange membrane water electrolyser operating at 1 A cm-2. This work bridges predictive modelling and experimental design, improving the electrocatalyst reliability for industrial water electrolysis and beyond at high current densities.

Oxygen evolution reaction on NiFe-LDH/(Ni,Fe)OOH: theoretical insights into the effects of electronic structure and spin-state evolution

NiFe-layered double hydroxides (NiFe-LDH) have emerged as promising oxygen evolution reaction (OER) catalysts in alkaline medium, but their commercial applications are limited due to the decrease in their activity as the electrolyte becomes less alkaline. Thus, a comprehensive understanding of the OER mechanism of NiFe-LDH in alkaline medium is desirable for the rational design of new catalysts with improved performances. Especially, their spin-related factors have rarely been systematically investigated during the OER (diamagnetic H2O → paramagnetic O2). Herein, we simulated the OER performance of NiFe-LDH and (Ni,Fe)OOH as NiFe-LDH underwent surface-reconstruction and formed (Ni,Fe)OOH under alkaline conditions. Results demonstrated an enhanced OER performance on (Ni,Fe)OOH, and the Fe active site of NiFe-LDH on losing 3H (namely, NiFe(OH)2 - 3H) showed the lowest overpotential for OER because the d-orbital electron of the Fe atom shifted up to the Fermi level. Notably, the electronic interaction between Fe and OOH induced a change in the spin state of Fe, which further decreased the overpotential for the OER. Thus, the overpotential of the Fe site on NiFe(OH)2 - 3H decreased from 0.55 eV to 0.46 eV. The density of states (DOS) analysis revealed that the spin flip of Fe promoted the formation of bonding states between Fe and OOH, endowing the catalyst with a better OER performance. Our findings can help pave the way for the development of high-performance OER catalysts at the spintronic level.

Structure, stability and electronic properties of two-dimensional monolayer noble metals with triangular lattices: Cu, Ag, and Au

First-principles calculations were performed to investigate the structure, stability, and electronic properties of two-dimensional noble metal monolayers, including Cu, Ag, and Au, inspired by the recent synthesis of a two-dimensional gold monolayer. All 2D noble metals exhibit great stability with almost standard equilateral triangular lattice structures. These monolayers can survive 10 ps MD annealing simulations under 300 K. Phonon spectra do not exhibit negative frequencies. The independent elastic constants, Young's modulus, and Poisson's ratio were obtained, indicating that these monolayers are mechanically stable and slightly anisotropic. Additionally, the results of band structures and density of states (DOS) calculations reveal typical metallic electronic properties. The dumbbell-like Fermi surfaces suggest anisotropic electron transport properties. These findings highlight the immense application potential of 2D noble metal monolayers in diverse fields.

Laser Ultrafast Confined Alloying of Sub-5 nm RuM (M = Cu, Rh, and Pd) Particles on Carbon Nanotubes for Hydrogen Evolution Reaction

Thermodynamic immiscibility is a challenge for intermetallic alloying of sub-5 nm Ru-based alloys, which are excellent electrochemical catalysts for water splitting. In this study, nanosecond laser ultrafast confined alloying (LUCA) is proposed to break the immiscible-to-miscible transition limit in the synthesis of carbon nanotubes (CNTs) supported sub-5 nm bimetallic RuM (M = Cu, Rh, and Pd) alloy nanoparticles (NPs). The alloying of non-noble metal Cu with varying atomic ratios of RuCu alloys is appealing owing to the low price of Cu and cost-effective synthesis for large-scale practical applications. Benefiting from the synergistic alloying effect and resultant H/OH binding energy alteration, the Ru95Cu5/CNTs catalysts display excellent electrocatalytic alkaline hydrogen evolution reaction (HER) activity with an overpotential of 17 mV and Tafel slope of 28.4 mV dec-1 at 10 mA cm-2, and high robustness over long-term 5000 cyclic voltammetry cycles. The performance is much better than LUCA-synthesized CNTs-supported Ru86Rh14, Ru89Pd11, Ru, and Cu NPs catalysts, commercial benchmark 20% Pt/C, and other mainstream Ru-based catalysts including wet chemistry-synthesized RuRh particles (overpotential of 25 mV, Tafel slope of 47.5 mVdec-1) and RuCu/CNTs (overpotential of 39 mV) synthesized using the flash Joule heating method, indicating the great potential of LUCA for screening new classes of HER catalysts.

Recent Advances of Electrocatalysts and Electrodes for Direct Formic Acid Fuel Cells: from Nano to Meter Scale Challenges

Direct formic acid fuel cells are promising energy devices with advantages of low working temperature and high safety in fuel storage and transport. They have been expected to be a future power source for portable electronic devices. The technology has been developed rapidly to overcome the high cost and low power performance that hinder its practical application, which mainly originated from the slow reaction kinetics of the formic acid oxidation and complex mass transfer within the fuel cell electrodes. Here, we provide a comprehensive review of the progress around this technology, in particular for addressing multiscale challenges from catalytic mechanism understanding at the atomic scale, to catalyst design at the nanoscale, electrode structure at the micro scale and design at the millimeter scale, and finally to device fabrication at the meter scale. The gap between the highly active electrocatalysts and the poor electrode performance in practical devices is highlighted. Finally, perspectives and opportunities are proposed to potentially bridge this gap for further development of this technology.

Pd1Ni2 Trimer Sites Drive Efficient and Durable Hydrogen Oxidation in Alkaline Media

Anion-exchange membrane fuel cell (AEMFC) is a cost-effective hydrogen-to-electricity conversion technology under a zero-emission scenario. However, the sluggish kinetics of the anodic hydrogen oxidation reaction (HOR) impedes the commercial implementation of AEMFCs. Here, we develop a Pd single-atom-embedded Ni3N catalyst (Pd1/Ni3N) with unconventional Pd1Ni2 trimer sites to drive efficient and durable HOR in alkaline media. Integrating theoretical and experimental analyses, we demonstrate that dual Pd1Ni2 sites achieve a "*H on Pd1Ni2-HV + *OH on Pd1Ni2-HN" adsorption mode, effectively weakening the overstrong *H and *OH adsorptions on pristine Ni3N. Owing to the unique coordination mode and atomically dispersed catalytic sites, the resulting Pd1/Ni3N catalyst delivers a high intrinsic and mass activity together with excellent antioxidation capability and CO tolerance. Specifically, the HOR mass activity of Pd1/Ni3N reaches 7.54 A mgPd-1 at the overpotential of 50 mV. The AEMFC employing Pd1/Ni3N as the anode catalyst displays a high power density of 31.7 W mgPd-1 with an ultralow anode precious metal loading of only 0.023 mgPd cm-2. This study provides guidance for the design of high-performance alkaline HOR catalytic sites at the atomic level.

Exploring the Conformational Space of a Sulfonyl-Based Ionic Liquid on Platinum-Based Mono and Bimetallic Surfaces

Understanding the arrangement of ionic liquids at the interface and their interactions with the surface is crucial for enhancing selectivity in heterogeneous reactions for practical applications. In this study, we investigate the nature of the adsorption and structural orientations of a sulfonyl-based ionic liquid on platinum-based mono- and bimetallic (111) surfaces employing replica exchange molecular dynamics and first-principles density functional theory calculations. More than 30 confirmations of the ionic liquid are identified on both monometallic and bimetallic surfaces. In addition to adsorption energies, factors such as dynamics of ionic liquids, molecule-surface distances, and charge transfer analyses are found to be important indicators for understanding adsorption phenomena. The sulfonyl anion exhibits contrasting behavior on the two surfaces, showing a preference for chemisorption on the monometallic surface, while the pyrrolidinium cation is physisorbed on both metal surfaces. Both metal surfaces are negatively charged primarily because of charge transfer from the sulfonyl anion. The analysis of the orientational preference reveals a nearly flat orientation of the cation on the monometallic surface, while a tilted orientation is observed on the bimetallic surface.

An Interstitial Boron Inserted Metastable Hexagonal Rh Nanocrystal for Efficient Hydrogen Oxidation Electrocatalysis

Constructing metastable phase structure plays an important role in changing the physicochemical properties and improving the catalytic performance of nanocrystals. Unfortunately, the synthesis of metastable phase metallic nanocrystals is highly challenging, mainly due to the thermodynamically unstable ground-state. Here, we report a synthesis of unconventional metastable hexagonal rhodium nanocrystal (Bint-Rhhcp/C) via interstitial boron insertion. The insertion of boron atoms into the interstitial sites of cubic Rh lattice not only induces the atomic arrangements from face-centered cubic (fcc) to hexagonal close-packed (hcp), but also stabilizes the metastable hexagonal Rh structure. Benefiting from the phase transition and interstitial boron doping, the Bint-Rhhcp/C catalyst exhibits remarkable catalytic performance toward hydrogen oxidation reaction (HOR) under alkaline media, with a mass activity of 1.413 mA μgPGM -1. Experimental measurements including in situ surface-enhanced infrared absorption spectroscopy (SEIRAS) and density functional theory (DFT) calculations indicate that the strengthened adsorption of hydroxyl species on the electrode surface of Bint-Rhhcp/C is responsible for the reconstruction of interfacial water structure and increased water proportions in the gap region in the electric double layers. As a result, the increased water connectivity and hydrogen bond network facilitate high-efficiency hydrogen transfer across the interface, thereby boost the alkaline HOR performance.

Tuning the d-Band Center of Nickel Bimetallic Compounds for Glycerol Chemisorption: A Density Functional Study

The modification of catalytic activity through the use of metallic promoters is a key strategy for optimizing performance, as electronic factors play a crucial role in regulating catalytic behavior. This study explores the electronic factors behind the adsorption of glycerol (Gly) on bimetallic nickel-based compounds (Ni3X) using density functional theory (DFT) calculations; incorporating Mn, Fe, Co, Cu, and Zn as promoters effectively tunes the d-band center of these systems, directly influencing their magnetic, adsorption, and catalytic properties. A good correlation between the calculated glycerol adsorption energy and the d-band filling of the studied bimetallic surfaces was identified. Interestingly, this correlation can be rationalized using the celebrated Newns-Anderson model based on the calculated d-band fillings and centers of the systems under study. Additionally, the adsorption energies and relative stability of other electro-oxidation intermediates toward dihydroxyacetone (DHA) were calculated. Notably, the Ni3Co and Ni3Cu systems exhibit an optimal balance between glycerol adsorption and DHA desorption, making them promising candidates for glycerol electro-oxidation. These theoretical insights address fundamental aspects of developing glycerol valorization processes and advancing alcohol electro-oxidation technologies in fuel cells with noble-metal-free catalysts.

Advanced electrocatalysts for fuel cells: Evolution of active sites and synergistic properties of catalysts and carrier materials

Proton exchange-membrane fuel cell (PEMFC) is a clean and efficient type of energy storage device. However, the sluggish reaction rate of the cathode oxygen reduction reaction (ORR) has been a significant problem in its development. This review reports the recent progress of advanced electrocatalysts focusing on the interface/surface electronic structure and exploring the synergistic relationship of precious-based and non-precious metal-based catalysts and support materials. The support materials contain non-metal (C/N/Si, etc.) and metal-based structures, which have demonstrated a crucial role in the synergistic enhancement of electrocatalytic properties, especially for high-temperature fuel cell systems. To improve the strong interaction, some exciting synergistic strategies by doping and coating heterogeneous elements or connecting polymeric ligands containing carbon and nitrogen were also shown herein. Besides the typical role of the crystal surface, phase structure, lattice strain, etc., the evolution of structure-performance relations was also highlighted in real-time tests. The advanced in situ characterization techniques were also reviewed to emphasize the accurate structure-performance relations. Finally, the challenge and prospect for developing the ORR electrocatalysts were concluded for commercial applications in low- and high-temperature fuel cell systems.

Transforming Plastics to Single Atom Catalysts for Peroxymonosulfate Activation: Axial Chloride Coordination Intensified Electron Transfer Pathway

Transforming plastics into single-atom catalysts is a promising strategy for upcycling waste plastics into value-added functional materials. Herein, a graphene-based single-atom catalyst with atomically dispersed FeN4Cl sites (Fe─N/Cl─C) is produced from high-density polyethylene wastes via one-pot catalytic pyrolysis. The Fe─N/Cl─C catalyst exhibited much higher turnover frequency and surface area normalized activity (Kac) compared with the Fe─N─C catalyst without axial Cl modulation. Both experiments and density functional theory (DFT) computations demonstrated that the axial incorporation of chloride fine-tuned the coordination environment of FeN4 sites and enhanced peroxymonosulfate (PMS) activation because of improved conductivity and modulated spin state. In situ, Raman, and infrared spectroscopic techniques revealed that PMS is activated by the Fe─N/Cl─C catalyst through an electron transfer process. The formation of a key PMS* intermediate at the Fe site effectively elevated the redox capacity of the catalyst surface to realize a fast degradation of diverse pollutants. The non-radical oxidation manner secures high selectivity toward target pollutants and high chemical utilization efficiency. A continuous operation in a column reactor also demonstrated the high efficiency and stability of the (Fe─N/Cl─C + PMS) system for practical water treatment.

Surface Structure Effects on H and O Adsorption on Gold, Nickel and Platinum Nanoparticles

Using quantum chemical modelling, in this work, we considered the structure effects determining the adsorption of H and O atoms on (111), (100), (110) and (211) surfaces of gold, nickel and platinum nanoparticles. Surface deformation enhanced the adatom bonding to active sites with a large coordination number on flat (111) and (100) surfaces, while no distinct tendency was observed on kinked (110) and (211) surfaces. The effect of the neighboring atoms depends on the coupling matrix element Vad2. For metals with a considerable matrix element, the adsorption energy decreases with the rise in coordination number, and vice versa.

Meso/Microporous Single-Atom Catalysts Featuring Curved Fe-N4 Sites Boost the Oxygen Reduction Reaction Activity

Zeolitic-imidazolate frameworks (ZIFs) are among the most efficient precursors for the synthesis of atomically dispersed Fe-N/C materials, which are promising catalysts for enhancing the performance of Zn-air batteries (ZABs) and proton exchange fuel cells (PEMFCs). However, existing ZIF-derived Fe-N/C electrocatalysts mostly consist of microporous materials, leading to insufficient mass transport and inadequate battery/cell performance. In this study, we synthesize an atomically dispersed meso/microporous Fe-N/C material with curved Fe-N4 active sites, denoted as FeSA-N/TC, through the pyrolysis of hemin-modified ZIF films on ZnO nanorods, obtained from the self-assembly reaction between Zn2+ from ZnO hydrolysis and 2-methylimidazole. Density functional theory calculations demonstrate that the curved Fe-N4 active sites can weaken the intermediate adsorptions, resulting in lower free energy barriers and enhanced performance during oxygen reduction reaction (ORR). Specifically, FeSA-N/TC exhibits exceptional ORR performance with half-wave potentials of 0.925 V in alkaline media and 0.825 V in acidic media. When used as the cathodic catalyst in PEMFCs and ZABs, FeSA-N/TC achieves high peak power densities (H2-O2 PEMFC: 1100 mW cm-2; H2-Air PEMFC: 715 mW cm-2; liquid-state ZAB: 228 mW cm-2; solid-state ZAB: 112 mW cm-2), demonstrating its feasibility and efficiency in practical applications.

A roadmap from the bond strength to the grain-boundary energies and macro strength of metals

Correlating the bond strength with the macro strength of metals is crucial for understanding mechanical properties and designing multi-principal-element alloys (MPEAs). Motivated by the role of grain boundaries in the strength of metals, we introduce a predictive model to determine the grain-boundary energies and strength of metals from the cohesive energy and atomic radius. This scheme originates from the d-band characteristics and broken-bond spirit of tight-binding models, and demonstrates that the repulsive/attractive effects play different roles in the variation of bond strength for different metals. Importantly, our framework not only applies to both pure metals and MPEAs, but also unravels the distinction of the bond strength caused by elemental compositions, lattice structures, high-entropy, and amorphous effects. These findings build a physical picture across bond strength, grain-boundary energies and strength of metals by using easily accessible material properties and provide a robust method for the design of high-strength alloys.

High-Throughput Screening Approach for Catalytic Applications through Regulation of Adsorption Energies via Work Function

Adsorption energy is critical in catalysis, energy storage, and sensing. Optimal adsorption energy on a catalytic substrate is essential as extreme adsorption energy can reduce the reaction efficiency. Building on our previous research on the influence of work function on adsorption energy (Phys. Chem. Chem. Phys. 2024, 26, 3525-3530), we examined a range of two-dimensional semiconductor materials, including black phosphorene, boron nitride, and MoS2, as supporting substrates for the construction of silicene-semiconductor heterojunctions. Furthermore, we analyzed how work function changes impact adsorption energy during O2 adsorption and developed a theoretical model to explain this relationship. The model was validated by demonstrating the regulation of the catalytic reaction barrier in the oxygen reduction reaction and was applied to N2 adsorption via high-throughput screening. Our findings demonstrate that the work function modulates the adsorption energy in van der Waals heterojunctions, enhancing catalytic efficiency. This approach aligns with the Sabatier principle and offers a pathway for optimizing catalysts.

Electrodegradation of nitrogenous pollutants in sewage: from reaction fundamentals to energy valorization applications

The excessive accumulation of nitrogen pollutants (mainly nitrate, nitrite, ammonia nitrogen, hydrazine, and urea) in water bodies seriously disrupts the natural nitrogen cycle and poses a significant threat to human life and health. Electrolysis is considered a promising method to degrade these nitrogenous pollutants in sewage, with the advantages of high efficiency, wide generality, easy operability, retrievability, and environmental friendliness. For particular energy devices, including metal-nitrate batteries, direct fuel cells, and hybrid water electrolyzers, the realization of energy valorization from sewage purification processes (e.g., valuable chemical generation, electricity output, and hydrogen production) becomes feasible. Despite the progress in the research on pollutant electrodegradation, the development of electrocatalysts with high activity, stability, and selectivity for pollutant removal, coupled with corresponding energy devices, remains a challenge. This review comprehensively provides advanced insights into the electrodegradation processes of nitrogenous pollutants and relevant energy valorization strategies, focusing on the reaction mechanisms, activity descriptors, electrocatalyst design, and actuated electrodes and operation parameters of tailored energy conversion devices. A feasibility analysis of electrodegradation on real wastewater samples from the perspective of pollutant concentration, pollutant accumulation, and electrolyte effects is provided. Challenges and prospects for the future development of electrodegradation systems are also discussed in detail to bridge the gap between experimental trials and commercial applications.

Material Engineering Strategies for Efficient Hydrogen Evolution Reaction Catalysts

Water electrolysis, a key enabler of hydrogen energy production, presents significant potential as a strategy for achieving net-zero emissions. However, the widespread deployment of water electrolysis is currently limited by the high-cost and scarce noble metal electrocatalysts in hydrogen evolution reaction (HER). Given this challenge, design and synthesis of cost-effective and high-performance alternative catalysts have become a research focus, which necessitates insightful understandings of HER fundamentals and material engineering strategies. Distinct from typical reviews that concentrate only on the summary of recent catalyst materials, this review article shifts focus to material engineering strategies for developing efficient HER catalysts. In-depth analysis of key material design approaches for HER catalysts, such as doping, vacancy defect creation, phase engineering, and metal-support engineering, are illustrated along with typical research cases. A special emphasis is placed on designing noble metal-free catalysts with a brief discussion on recent advancements in electrocatalytic water-splitting technology. The article also delves into important descriptors, reliable evaluation parameters and characterization techniques, aiming to link the fundamental mechanisms of HER with its catalytic performance. In conclusion, it explores future trends in HER catalysts by integrating theoretical, experimental and industrial perspectives, while acknowledging the challenges that remain.

High-throughput screening of bifunctional catalysts for oxygen evolution/reduction reaction at the subnanometer regime

The development of low-cost, stable, and highly efficient electrocatalysts for the bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for advancing future renewable technologies. In this study, we systematically investigated the OER and ORR performance of subnano clusters across the 3d, 4d, and 5d transition metal (TM) series of varying sizes using first-principles calculations. The fluxional identity of these clusters in the subnanometer regime is reflected in their non-monotonic catalytic activity. We established a size-dependent scaling relationship between OER/ORR intermediates, leading to a reshaping of the activity volcano plot at the subnanometer scale. Our detailed mechanistic investigation revealed a shift in the apex of the activity volcano from the Pt(111) and IrO2 surfaces to the Au11 clusters for both OER and ORR. Late transition metal subnano clusters, specifically Au11, emerged as the best bifunctional electrocatalyst, demonstrating significantly lower overpotential values. Furthermore, we categorized our catalysts into three clusters and employed the Random Forest Regression method to evaluate the impact of non-ab initio electronic features on OER and ORR activities. Interestingly, d-band filling emerged as the primary contributor to the bifunctional activity of the subnano clusters. This work not only provides a comprehensive view of OER and ORR activities but also presents a new pathway for designing and discovering highly efficient bifunctional catalysts.

Cooperative Use of N-Heterocyclic Carbenes and Thiols on a Silver Surface: A Synergetic Approach to Surface Modification

Surface modification through the formation of a self-assembled monolayer (SAM) can effectively engineer the physicochemical properties of the surface/material. However, the precise design of multifunctional SAMs at the molecular level is still a major challenge. Here, we jointly use N-heterocyclic carbenes (NHCs) and thiols to form multifunctional hetero-SAM systems that demonstrate excellent chemical stability, electrical conductivity, and, in silico, catalytic activity. This synergistic effect is facilitated by the high surface mobility and electron-rich nature of NHCs, combined with the strong binding strength of thiols. Scanning tunneling microscopy, electrical conductivity, and scanning electron microscope measurements, as well as density functional theory calculations, were employed to explore the synergistic interactions in the supramolecular SAMs. The van der Waals integration of ballbot-type NHCs and thiols enables the SAMs to exhibit both superior surface anticorrosion properties (attributing to the shift in the d-band center) and low surface resistance originating from the band alignment. Moreover, we find that the deposition sequence of flat-lying NHCs and thiols results in SAMs with different configurations, which can further tune the mechanistic pathway in silico in the acetylene hydrogenation process. Our results provide essential molecular insights into the local electronic control of the new SAM/metal interface and the high stability of the emergent multifunctionality (NHC/thiol)-SAMs forming self-assembled lamellae structures in the nanometer regime.

Machine-Learning-Assisted Screening of Nanocluster Electrocatalysts: Mapping and Reshaping the Activity Volcano for the Oxygen Reduction Reaction

In computational heterogeneous catalysis, Sabatier's principle-based activity volcano plots provide an intuitive guide to catalyst design but impose a fundamental constraint on the maximum achievable catalytic performance. Recently, subnano clusters have emerged as an exciting platform, offering high noble metal utilization and superior performance for various reactions compared to extended surfaces, reflecting a complex structure-activity relationship in the non-scalable regime. However, understanding their non-monotonic catalytic activity, attributed to the large configurational space and their fluxional identity, poses a formidable challenge. Here, we present a machine learning (ML) framework that captures the non-monotonic trends in oxygen reduction reaction (ORR) activity at the subnanometer scale, attributed to their dynamic fluxional characteristics. We demonstrate a size-dependent shifting and reshaping of the ORR activity volcano, with Au replacing Pt at the peak. Leveraging only upon the non-ab initio geometric and electronic properties, our trained ML model accurately captures the site-specific adsorption energies of intermediates at the subnanometer regime. To account for the inconsistent trend in activity, we analyzed the correlation between electronic and geometric properties. Our findings reveal that the d-filling and coupling matrix of the neighboring metal atom significantly influences the intermediate adsorption on the local chemical environment compared to the d-band center. Following this analysis, we utilized ML to map the catalyst distribution in the activity volcano and identified the five best sub-nano electrocatalysts, demonstrating overpotential values lower than or comparable to the Pt(111) surface for the ORR. This study provides intuitive guidelines for the rational designing of highly efficient electrocatalysts for fuel cell applications while modifying the activity volcano plots for electrocatalysts at the subnanometer regime.

Molybdenum Carbide Catalyst Enables Efficient Conversion of Chlorinated Volatile Organic Waste into Syngas through Catalytic Steam Reforming

Catalytic steam reforming offers a groundbreaking approach for converting industrial chlorinated volatile organic compound (CVOC) waste into valuable syngas (H2 and CO) and recovering HCl. However, the lack of C-Cl bond activation ability in traditional transition metal catalysts results in their insufficient reforming activity toward CVOCs. Herein, a novel molybdenum carbide (β-Mo2C) catalyst is developed and loaded onto a γ-Al2O3 support synthesized through a self-assembly method. The γ-Al2O3 support provides abundant unsaturated coordinated Al3+ ions, which effectively anchor and disperse β-Mo2C nanoparticles. In the catalytic steam reforming reaction at 600 °C, the β-Mo2C/γ-Al2O3 catalyst achieves a conversion efficiency higher than 95% and syngas yields of 82.4-92.3% for various typical industrial CVOCs. The mechanistic research reveals that the coordination between C and Mo atoms in β-Mo2C leads to a slightly electron-deficient state of the Mo sites, accompanied by a high density of unoccupied 4d orbitals. These characteristics are highly advantageous for the adsorption and dechlorination of CVOC molecules. The produced nonchlorinated intermediates can subsequently be oxidized to CO and H2 by hydroxyl radicals on adjacent Mo sites.

Coupling High-Entropy Core with Rh Shell for Efficient pH-Universal Hydrogen Evolution

Constructing high-entropy alloys (HEAs) with core-shell (CS) nanostructure is efficient for enhancing catalytic activity. However, it is extremely challenging to incorporate the CS structure with HEAs. Herein, PtCoNiMoRh@Rh CS nanoparticles (PtCoNiMoRh@Rh) with ∼5.7 nm for pH-universal hydrogen evolution reaction (HER) are reported for the first time. The PtCoNiMoRh@Rh just require 9.1, 24.9, and 17.1 mV to achieve -10 mA cm-2 in acid, neutral, and alkaline electrolyte, and the corresponding mass activity are 5.8, 2.79, and 91.8 times higher than that of Rh/C. Comparing to PtCoNiMoRh nanoparticles, the PtCoNiMoRh@Rh exhibit excellent HER activity attributed to the decrease of Rh 4d especially 4d5/2 unoccupied state induced by the multi-active sites in HEA, as well as the synergistic effect in Rh shell and HEA core. Theorical calculation exhibits that Rh-dyz, dx2, and dxz orbitals experience a negative shift with shell thickness increasing. The HEAs with CS structure would facilitate the rational design of high-performance HEAs catalysts.

Crystal-Phase- and B-Content-Dependent Electrochemical Behavior of Pd─B Nanocrystals toward Oxygen Reduction Reaction

The manipulation of crystal phases in metal-nonmetal interstitial alloy nanostructures has attracted considerable attention due to the formation of unique electronic structures and surface atomic arrangements, resulting in unprecedented catalytic performances. However, achieving simultaneous control over crystal phase and nonmetal elements in metal-nonmetal interstitial alloy nanostructures has remained a formidable challenge. Here, a novel synthesis approach is presented for Pd─B interstitial alloy nanocrystals (NCs) that allows investigation of the crystal-phase- and B-content-dependent catalytic performance. Through comparison of the oxygen reduction reaction (ORR) properties of Pd─BX interstitial alloy NCs with different crystal phases and B contents, achieved by precise control of reaction temperature and time, the influences of crystal phase and B contents in the Pd─BX interstitial alloy NCs on ORR are precisely investigated. The hexagonal closed packed (hcp) PdB0.5 NCs exhibit superior catalytic activity, with mass activities reaching 2.58 A mg-1, surpassing Pd/C by 10.3 times, attributed to synergistic effects by the hcp crystal phase and relatively high B contents. This study not only provides a novel approach to fabricate interstitial alloy nanostructures with unconventional crystal phases and finely controlled nonmetal elements but also elucidates the importance of crystal phase and nonmetal element content in optimizing electrocatalytic efficiency.

Fine-Tuning the d-Band Center Position of Zinc to Increase the Anti-Tumor Activity of Single-Atom Nanozymes

The exceptional biocompatibility of Zn-based single-atom nanozymes (SAzymes) has led to extensive research in their application for disease diagnosis and treatment. However, the fully occupied 3d10 electron configuration has seriously hampered the enzymatic-like activity of Zn-based SAzymes. Herein, a B-doped Zn-based SAzymes is fabricated by carbonizing zeolite-like Zn-based boron imidazolate framework at different temperatures (Zn-SAs@BNCx, x = 800, 900, 1000, and 1100 °C). The formed B─N bond yielded a local electric field, which changes the position of the d-band center and improved the oxidation state of Zn by facilitating the electron transfer from Zn to N to B. These changes enhanced the adsorption and activation of H2O2 and O2 by Zn-SAs@BNC1000, increasing the nanozymes' multi-enzyme catalytic activity. B doping led to 24.81-, 32.37-, and 13.98-fold increase in the peroxidase-, oxidase- and catalase-like, respectively, catalytic efficiency (Kcat/Km) of Zn-SAs@BNC1000 when compared with no B doping. In addition, Zn-SAs@BNC1000 showed excellent ability to kill tumor cells both in vitro and in vivo. This study demonstrates that the modulation of the electron configuration of Zn is an effective strategy to develop efficient anti-tumor approaches by boosting the enzymatic activity of Zn-based SAzymes.

DFT study on the mechanism of methanol dehydrogenation over RuxPy surfaces

Methanol dehydrogenation (MD) is highly valuable in hydrogen energy production, and the introduction of nonmetals has received much attention to improve the activity and stability of the MD catalysts, but the understanding of the role of non-metallic elements in catalyzing the MD reaction is rather limited. Density functional theory (DFT) is employed to investigate the mechanism of methanol dehydrogenation on RuxPy surfaces. In this work, the P element is introduced into the Ru-based catalyst to obtain dispersed Ru sites and RuxPy (x/y = 2 : 1, 1 : 1, and 1 : 2) catalysts are designed. CH3OH adsorption, electronic structure of the catalyst, energy barriers for carbon accumulation reactions, and the mechanism of methanol decomposition are systematically calculated. The results of the effective reaction barrier (Eeffa) reveal that the order of the activity of the MD reaction is RuP(112) > Ru(0001) > Ru2P(210) > RuP2(110). The most preferable pathway on RuP(112) is pathway 1 (CH3OH* → CH3O* → CH2O* → CHO* → CO*). After the introduction of P, the weakened CO adsorption enhanced the resistance of catalysts to CO poisoning, and the activation energy of the carbon accumulation reaction increased, indicating that the anti-coking ability of the catalysts is improved. This theoretical study contributes to the design and modulation of highly active and stable metal catalysts for MD reactions.

Selective and durable H2O2 electrosynthesis catalyst in acid by selenization induced straining and phasing

Developing efficient electrocatalysts for acidic electrosynthesis of hydrogen peroxide (H2O2) holds considerable significance, while the selectivity and stability of most materials are compromised under acidic conditions. Herein, we demonstrate that constructing amorphous platinum-selenium (Pt-Se) shells on crystalline Pt cores can manipulate the oxygen reduction reaction (ORR) pathway to efficiently catalyze the electrosynthesis of H2O2 in acids. The Se2‒Pt nanoparticles, with optimized shell thickness, exhibit over 95% selectivity for H2O2 production, while suppressing its decomposition. In flow cell reactor, Se2‒Pt nanoparticles maintain current density of 250 mA cm-2 for 400 h, yielding a H2O2 concentration of 113.2 g L-1 with productivity of 4160.3 mmol gcat-1 h-1 for effective organic dye degradation. The constructed amorphous Pt-Se shell leads to desirable O2 adsorption mode for increased selectivity and induces strain for optimized OOH* binding, accelerating the reaction kinetics. This selenization approach is generalizable to other noble metals for tuning 2e‒ ORR pathway.

Enhancement of single-atom catalytic activity by the synergistic effect of interlayer charge transfer and magnetic coupling in an electride-based heterostructure

2D material-based single-atom catalysts have rapidly emerged and flourished in recent years due to their exceptional atomic utilization efficiency, adjustable catalytic activity, and remarkably high selectivity. The interface matching mechanism of 2D materials, influenced by van der Waals (vdW) interactions, presents a novel opportunity for constructing a heterostructure, further augmenting catalytic efficiency. In this work, the mechanism of performance regulation of magnetic transition-metal decorated MoS2 single-atom catalysis by importing a Gd2C electride substrate is investigated using first-principles calculations. The localization of d orbitals in transition-metals is weakened by adding a Gd2C substrate, thereby modulating the catalytic performance. Our findings demonstrate that the formation of an electron layer at the interface of the heterostructure by electride Gd2C induces a modification in the chemical environment of the MoS2 surface. The electron layer enhances the electron transfer during catalysis. Additionally, for the catalyst containing magnetic atoms, Gd2C can also achieve catalytic performance adjustment due to the magnetic coupling, similar to the effect of external magnetic fields. This study offers a novel concept and a pathway for enhancing the performance of single-atom catalysts through the construction of a heterostructure, capitalizing on the distinctive electron layer of an electride and its inherent high magnetic moments.

Selenium Adsorption on the (111), (100), (110) and (211) surfaces of Face-Centered-Cubic Metals: Density Functional Calculations of the Potential Energy Surfaces

In this study, we expand the computational investigation of selenium, which has previously been limited to metals such as Cu, Fe, Pd, Au, and Pt. Utilizing density functional theory calculations, we explore the adsorption and diffusion of selenium at a low-coverage regime of 0.25 ML on a broader range of metal surfaces, including Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au. Our results reveal that selenium exhibits a distinct preference for three-fold or four-fold high-coordination sites on most studied surfaces. We further analyze the minimum energy diffusion pathways, demonstrating that the energy barrier for selenium's surface diffusion varies significantly based on the orientation and nature of the metal surfaces. Specifically, on (100) surfaces, selenium exhibits the highest diffusion energy, ranging from 0.60 eV in Au(100) to 1.12 eV in Pd(100). The diffusion behavior on (110) and (211) surfaces is also elaborated, emphasizing the unique trends observed compared to previously studied elements like sulfur. Importantly, this study is a new reference for future computational analyses, filling existing gaps by providing comprehensive data on selenium adsorption on various face-centered cubic metal surfaces not previously reported.

Tailored interface engineering of Co3Fe7/Fe3C heterojunctions for enhancing oxygen reduction reaction in zinc-air batteries

The rational construction of highly active and robust non-precious metal oxygen reduction electrocatalysts is a vital factor to facilitate commercial applications of Zn-air batteries. In this study, a precise and stable heterostructure, comprised of a coupling of Co3Fe7 and Fe3C, was constructed through an interface engineering-induced strategy. The coordination polymerization of the resin with the bimetallic components was meticulously regulated to control the interfacial characteristics of the heterostructure. The synergistic interfacial effects of the heterostructure successfully facilitated electron coupling and rapid charge transfer. Consequently, the optimized CST-FeCo displayed superb oxygen reduction catalytic activity with a positive half-wave potential of 0.855 V vs. RHE. Furthermore, the CST-FeCo air electrode of the liquid zinc-air battery revealed a large specific capacity of 805.6 mAh gZn-1, corresponding to a remarkable peak power density of 162.7 mW cm-2, and a long charge/discharge cycle stability of 220 h, surpassing that of the commercial Pt/C catalyst.

Single Atom Ag Bonding Between PF3T Nanocluster and TiO2 Leads the Ultra-Stable Visible-Light-Driven Photocatalytic H2 Production

Atomic Ag cluster bonding is employed to reinforce the interface between PF3T nano-cluster and TiO2 nanoparticle. With an optimized Ag loading (Ag/TiO2 = 0.5 wt%), the Ag atoms will uniformly disperse on TiO2 thus generating a high density of intermediate states in the band gap to form the electron channel between the terthiophene group of PF3T and the TiO2 in the hybrid composite (denoted as T@Ag05-P). The former expands the photon absorption band width and the latter facilitates the core-hole splitting by injecting the photon excited electron (from the excitons in PF3T) into the conduction band (CB) of TiO2. These characteristics enable the high efficiency of H2 production to 16 580 µmol h-1 g-1 and photocatalysis stability without degradation under visible light exposure for 96 h. Compared to that of hybrid material without Ag bonding (TiO2@PF3T), the H2 production yield and stability are improved by 4.1 and 18.2-fold which shows the best performance among existing materials in similar component combination and interfacial reinforcement. The unique bonding method offers a new prospect to accelerate the development of photocatalytic hydrogen production technologies.

Kinetic Insights into Methanol Synthesis from CO2 Hydrogenation at Atmospheric Pressure over Intermetallic Pd2Ga Catalyst

This study presents a single-site microkinetic model for methanol synthesis by CO2 hydrogenation over intermetallic Pd2Ga/SiO2. A reaction path analysis (RPA) combining theoretical results and realistic catalyst surface reaction data is established to elucidate the reaction mechanism and kinetic models of CO2 hydrogenation to methanol and CO. The RPA leads to the derivation of rate expressions for both reactions without presumptions about the most abundant reactive intermediate (MARI) and rate-determining step (rds). The formation of H2COOH* is found to be the rds (step 19) for methanol synthesis via the formate pathway, with CO2 and H-atoms adsorbed on intermetallic sites as the MARIs. The derived kinetic model is corroborated with experimental data acquired under different reaction conditions, using a lab-scale fixed-bed reactor and Pd2Ga/SiO2 nanoparticles prepared by incipient wetness impregnation. The excellent agreement between the experimental data and the kinetic model (R 2 = 0.99) substantiates the proposed mechanism with an activation energy of 61.52 kJ mol-1 for methanol synthesis. The reported catalyst exhibits high selectivity to methanol (96%) at 1 bar, 150 °C, and H2/CO2 ratio of 3:1. These findings provide critical insights to optimize catalysts and processes targeting CO2 hydrogenation at atmospheric pressure and low temperatures for on-demand energy production.

Ultra-Rapid Electrocatalytic H2O2 Fabrication over Mono-Species and High-Density Polypyrrolic-N Sites

Electrocatalytic hydrogen peroxide (H2O2) production via two-electron oxygen reduction reaction (2e--ORR) features energy-saving and eco-friendly characteristics, making it a promising alternative to the anthraquinone oxidation process. However, the common existence of numerous 2e--ORR-inactive sites/species on electrocatalysts tends to catalyze side reactions, especially under low potentials, which compromises energy efficiency and limits H2O2 yield. Addressing this, a high surface density of mono-species pyrrolic nitrogen configurations is formed over a polypyrrole@carbon nanotube composite. Thermodynamic and kinetic calculation and experimental investigation collaboratively confirm that these densely distributed and highly selective active sites effectively promote high-rate 2e--ORR electrocatalysis and inhibit side reactions over a wide potential range. Consequently, an ultra-high and stable H2O2 yield of up to 67.9/51.2 mol g-1 h-1 has been achieved on this material at a current density of 200/120 mA cm-1, corresponding Faradaic efficiency of 72.8/91.5%. A maximum H2O2 concentration of 13.47 g L-1 can be accumulated at a current density of 80 mA cm-1 with satisfactory stability. The strategy of surface active site densification thus provides a promising and universal avenue toward designing highly active and efficient electrocatalysts for 2e--ORR as well as a series of other similar electrochemical processes.

Halogen Tailoring of Platinum Electrocatalyst with High CO Tolerance for Methanol Oxidation Reaction

The catalytic activity of platinum for CO oxidation depends on the interaction of electron donation and back-donation at the platinum center. Here we demonstrate that the platinum bromine nanoparticles with electron-rich properties on bromine bonded with sp-C in graphdiyne (PtBr NPs/Br-GDY), which is formed by bromine ligand and constitutes an electrocatalyst with a high CO-resistant for methanol oxidation reaction (MOR). The catalyst showed peak mass activity for MOR as high as 10.4 A mgPt -1, which is 20.8 times higher than the 20 % Pt/C. The catalyst also showed robust long-term stability with slight current density decay after 100 hours at 35 mA cm-2. Structural characterization, experimental, and theoretical studies show that the electron donation from bromine makes the surface of platinum catalysts highly electron-rich, and can strengthen the adsorption of CO as well as enhance π back-donation of Pt to weaken the C-O bond to facilitate CO electrooxidation and enhance catalytic performance during MOR. The results highlight the importance of electron-rich structure among active sites in Pt-halogen catalysts and provide detailed insights into the new mechanism of CO electrooxidation to overcome CO poisoning at the Pt center on an orbital level.

Highly Dispersed Pd-CeOx Nanoparticles in Zeolite Nanosheets for Efficient CO2-Mediated Hydrogen Storage and Release

Formic acid (FA) dehydrogenation and CO2 hydrogenation to FA/formate represent promising methodologies for the efficient and clean storage and release of hydrogen, forming a CO2-neutral energy cycle. Here, we report the synthesis of highly dispersed and stable bimetallic Pd-based nanoparticles, immobilized on self-pillared silicalite-1 (SP-S-1) zeolite nanosheets using an incipient wetness co-impregnation technique. Owing to the highly accessible active sites, effective mass transfer, exceptional hydrophilicity, and the synergistic effect of the bimetallic species, the optimized PdCe0.2/SP-S-1 catalyst demonstrated unparalleled catalytic performance in both FA dehydrogenation and CO2 hydrogenation to formate. Remarkably, it achieved a hydrogen generation rate of 5974 molH2 molPd -1 h-1 and a formate production rate of 536 molformate molPd -1 h-1 at 50 °C, surpassing most previously reported heterogeneous catalysts under similar conditions. Density functional theory calculations reveal that the interfacial effect between Pd and cerium oxide clusters substantially reduces the activation barriers for both reactions, thereby increasing the catalytic performance. Our research not only showcases a compelling application of zeolite nanosheet-supported bimetallic nanocatalysts in CO2-mediated hydrogen storage and release but also contributes valuable insights towards the development of safe, efficient, and sustainable hydrogen technologies.

Design of Multifunctional Electrocatalysts for ORR/OER/HER/HOR: Janus Makes Difference

Multifunctional electrocatalysts for hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) have broad application prospects; However, realization of such kinds of materials remain difficulties because it requires the materials to have not only unique electronic properties, but multiple active centers to deal with different reactions. Here, employing density functional theory (DFT) computations, it is demonstrated that by decorating the Janus-type 2D transition metal dichalcogenide (TMD) of TaSSe with the single atoms, the materials can achieve multifunctionality to catalyze the ORR/OER/HER/HOR. Out of sixteen catalytic systems, Pt-VS (i.e., Pt atom embedded in the sulfur vacancy), Pd-VSe, and Pt-VSe@TaSSe are promising multifunctional catalysts with superior stability. Among them, the Pt-VS@TaSSe catalyst exhibits the highest activity with theoretical overpotentials ηORR = 0.40 V, ηOER = 0.39 V, and ηHER/HOR = 0.07 V, respectively, better than the traditional Pt (111), IrO2 (110). The interplays between the catalyst and the reaction intermediate over the course of the reaction are then systematically investigated. Generally, this study presents a viable approach for the design and development of advanced multifunctional electrocatalysts. It enriches the application of Janus, a new 2D material, in electrochemical energy storage and conversion technology.