Improving the Performance of Pd for Formic Acid Dehydrogenation by Introducing Barium Titanate

Formic acid, a safe and widely available organic compound, produces hydrogen under mild conditions, with the existence of Pd-based catalysts. Efficiently generating hydrogen via formic acid decomposition (FAD) is restricted by the cleavage of the C-H bond in adsorbed HCOO* and strong adsorption of hydrogen on the Pd surface. Herein, tetragonal-phase barium titanate (TBT) was in situ grown on reduced graphene oxide (rGO) to support Pd (Pd/TBT/rGO) for FAD. The internal electric field exists around TBT owing to its spontaneous polarization capacity. The physical characterizations illustrate that the introduction of barium titanate affects the catalytic performance of the catalyst by decreasing the particle size of Pd nanoparticles (NPs) and forming electron-rich Pd. The as-synthesized Pd/TBT/rGO exhibited excellent catalytic activity and hydrogen selectivity for FAD with a high initial turnover frequency up to 3019.72 h-1 at 333 K. The reason for this enhancement is not only the small-size Pd NPs but also the internal electric field from TBT, which promotes the desorption of adsorbed hydrogen on the Pd surface. Additionally, the electron-rich Pd is favorable to the cleavage of the C-H bond in HCOO*. This work will improve the understanding of the characterization of barium titanate and provide a new design strategy for the FAD catalyst.

Dual Function of Naphthalenediimide Supramolecular Photocatalyst with Giant Internal Electric Field for Efficient Hydrogen and Oxygen Evolution

Organic supramolecular photocatalysts have garnered widespread attention due to their adjustable structure and exceptional photocatalytic activity. Herein, a novel bis-dicarboxyphenyl-substituent naphthalenediimide self-assembly supramolecular photocatalyst (SA-NDI-BCOOH) with efficient dual-functional photocatalytic performance is successfully constructed. The large molecular dipole moment and short-range ordered stacking structure of SA-NDI-BCOOH synergistically create a giant internal electric field (IEF), resulting in a remarkable 6.7-fold increase in its charge separation efficiency. Additionally, the tetracarboxylic structure of SA-NDI-BCOOH greatly enhances its hydrophilicity. Thus, SA-NDI-BCOOH demonstrates efficient dual-functional activity for photocatalytic hydrogen and oxygen evolution, with rates of 372.8 and 3.8 µmol h-1 , respectively. Meanwhile, a notable apparent quantum efficiency of 10.86% at 400 nm for hydrogen evolution is achieved, prominently surpassing many reported supramolecular photocatalysts. More importantly, with the help of dual co-catalysts, it exhibits photocatalytic overall water splitting activity with H2 and O2 evolution rates of 3.2 and 1.6 µmol h-1 . Briefly, this work sheds light on enhancing the IEF by controlling the molecular polarity and stacking structure to dramatically improve the photocatalytic performance of supramolecular materials.

Enhanced Photocatalytic Properties of All-Organic IDT-COOH/O-CN S-Scheme Heterojunctions Through π-π Interaction and Internal Electric Field

Herein, we present a distinct methodology for the in situ electrostatic assembly method for synthesizing a conjugated (IDT-COOH)/oxygen-doped g-C3N4 (O-CN) S-scheme heterojunction. The electron delocalization effect due to π-π interactions between O-CN and self-assembled IDT-COOH favors interfacial charge separation. The self-assembled IDT-COOH/O-CN exhibits a broadened visible absorption to generate more charge carriers. The internal electric field between the IDT-COOH and the O-CN interface provides a directional charge-transfer channel to increase the utilization of photoinduced charge carriers. Moreover, the active species (•O2-, h+, and 1O2) produced by IDT-COOH/O-CN under visible light play important roles in photocatalytic disinfection. The optimum 40% IDT-COOH/O-CN can kill 7-log of methicillin-resistant Staphylococcus aureus (MRSA) cells in 2 h and remove 88% tetracycline (TC) in 5 h, while O-CN only inactivates 1-log of MRSA cells and degrades 40% TC. This work contributes to a promising method to fabricate all-organic g-C3N4-based S-scheme heterojunction photocatalysts with a wide range of optical responses and enhanced exciton dissociation.

Unlocking Bimetallic Active Centers via Heterostructure Engineering for Exceptional Phosphate Electrosorption: Internal Electric Field-Induced Electronic Structure Reconstruction

Development of electrode materials exhibiting exceptional phosphate removal performance represents a promising strategy to mitigate eutrophication and meet ever-stricter stringent emission standards. Herein, we precisely designed a novel LaCeOx heterostructure-decorated hierarchical carbon composite (L8C2PC) for high-efficiency phosphate electrosorption. This approach establishes an internal electric field within the LaCeOx heterostructure, where the electrons transfer from Ce atoms to neighboring La atoms through superexchange interactions in La-O-Ce coordination units. The modulatory heterostructure endows a positive shift of the d band of La sites and the increase of electron density at Fermi level, promoting stronger orbital overlap and binding interactions. The introduction of oxygen vacancies during the in situ nucleation process reduces the kinetic barrier for phosphate-ion migration and supplies additional active centers. Moreover, the hierarchical carbon framework ensures electrical double-layer capacitance for phosphate storage and interconnected ion migration channels. Such synergistically multiple active centers grant the L8C2PC electrode with high-efficiency record in phosphate electrosorption. As expected, the L8C2PC electrode demonstrates the highest removal capability among the reported electrode materials with a saturation capacity of 401.31 mg P g-1 and a dynamic capacity of 91.83 mg P g-1 at 1.2 V. This electrochemical system also performs well in the dephosphorization in natural water samples with low concentration that enable effluent concentration to meet the first-class discharge standard for China (0.5 mg P L-1). This study advances efficient dephosphorization techniques to a new level and offers a deep understanding of the internal electric field that regulates metal orbitals and electron densities in heterostructure engineering.

Efficient Charge Separation and Transport in Fullerene-CuPcOC8 Donor-Acceptor Nanorod Enhancing Photocatalytic Hydrogen Generation

Photocatalytic hydrogen generation via water decomposition is a promising avenue in the pursuit of large-scale, cost-effective renewable hydrogen energy generation. However, the design of an efficient photocatalyst plays a crucial role in achieving high yields in hydrogen generation. Herein, we have engineered a fullerene-2,3,9,10,16,17,23,24-octa(octyloxy)copper phthalocyanine (C60-CuPcOC8) photocatalyst, achieving both efficient hydrogen generation and high stability. The significant donor-acceptor (D-A) interactions facilitate the efficient electron transfer from CuPcOC8 to C60. The rate of photocatalytic hydrogen generation for C60-CuPcOC8 is 8.32 mmol·g-1·h-1, which is two orders of magnitude higher than the individual C60 and CuPcOC8. The remarkable increase in hydrogen generation activity can be attributed to the development of a robust internal electric field within the C60-CuPcOC8 assembly. It is 16.68 times higher than that of the pure CuPcOC8. The strong internal electric field facilitates the rapid separation within 0.6 ps, enabling photogenerated charge transfer efficiently. Notably, the hydrogen generation efficiency of C60-CuPcOC8 remains above 95%, even after 10 h, showing its exceptional photocatalytic stability. This study provides critical insight into advancing the field of photocatalysis.

Internal Electric Field-Modulated Charge Migration Behavior in MoS2 /MIL-53(Fe) S-Scheme Heterojunction for Boosting Visible-Light-Driven Photocatalytic Chlorinated Antibiotics Degradation

Inadequate photo-generated charge separation, migration, and utilization efficiency limit the photocatalytic efficiency. Herein, a MoS2 /MIL-53(Fe) photocatalyst/activator with the S-scheme heterojunction structure is designed and the charge migration behavior is modulated by the internal electric field (IEF). The IEF intensity is enhanced to 40 mV by modulating band bending potential and the depletion layer length of MoS2 . The photo-generated electron migration process is boosted by constructing the electron migration bridge (Fe-O-S) and modulating the IEF as the driving force, confirmed by the density functional theory calculation. Compared with the pristine materials, the photocurrent density of MoS2 /MIL-53(Fe) is significantly enhanced 27.5 times. Contributed by the visible-light-driven cooperative catalytic degradation and the high-efficiency direct photo-generated electron reduction dichlorination process, satisfactory chlorinated antibiotics removal and detoxification performances are achieved. This study opens up new insights into the application of heterojunctions in photocatalytic activation of PDS in environmental remediation.

A Surface Matrix of Au NPs Decorated Graphdiyne for Multifunctional Laser Desorption/Ionization Mass Spectrometry

The development of the valid strategy to enhance laser desorption/ionization efficiency gives rise to widespread concern in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) technology. Herein, a hybrid of Au NP-decorated graphdiyne (Au/GDY) was fabricated and employed as the SALDI-MS matrix for the first time, and a mechanism based on photothermal and photochemical energy conversions was proposed to understand LDI processes. Given theoretical simulations and microstructure characterizations, it was revealed that the formation of a coupled thermal field and internal electric field endow the as-prepared Au/GDY matrix with superior desorption and ionization efficiency, respectively. Moreover, laser-induced matrix ablation introduced strain and defect level into the Au/GDY hybrid, suppressing the recombination of charge carriers and thereby facilitating analyte ionization. The optimized Au/GDY matrix allowed for reliable detection of trace sulfacetamide and visualization of exogenous/endogenous components in biological tissues. This work offers an integrated solution to promote LDI efficiency based on collaborative photothermal conversion and internal electric field, and may inspire the design of novel semiconductor-based surface matrices.

Internal Electric Field Induced by Superexchange Interaction on Mn4+ -O2- -Ni2+ Unit Enables Highly Efficient Hybrid Capacitive Deionization

Internal electric field (IEF) construction is an innovative strategy to regulate the electronic structure of electrode materials to promote charge transfer processes. Despite the wide use of IEF in various applications, the underlying mechanism of its formation in an asymmetric TM-O-TM unit still remains poorly understood. Herein, the essential principles for the IEF construction at electron occupancy state level and explore its effect on hybrid capacitive deionization (HCDI) performance is systematically investigated. By triggering a charge separation in Ni-MnO2 via superexchange interactions in a coordination structure unit of Mn4+ -O2- -Ni2+ , the formation of an IEF that can enhance charge transfer during the HCDI process is demonstrated. Experimental and theoretical results confirm the electrons transfer from O 2p orbital to TM (Ni2+ and Mn4+ ) eg orbital via superexchange interactions in the basic Mn4+ -O2- -Ni2+ coordination unit. As a result of the charge redistribution, the IEF endows Ni-MnO2 with superior electron and ion transfer property. This work presents a unique material design strategy that activates the electrochemical performance, and provides insights into the formation mechanism of IEF in an asymmetric TM-O-TM unit, which has potential applications in the construction of other innovative materials.

Internal Electric Field Built on Heterointerface of H2TiO3/H4Ti5O12 Hybrid Enabling Promoted Li Extraction Performance

With potentially high lithium (Li) exchange capacity and long cycle ability, Ti-based oxides of H₂TiO₃ and H₄Ti₅O₁₂ are considered to be promising Li-ion sieve (LIS) materials applied for Li resource extraction in the liquid phase. However, the LISs usually demonstrate unsatisfactory Li exchange performance under the approximately neutral condition without the strong impetus derived from the rapid combination between OH^- in the surrounding solution and H⁺ ionized from LIS. Herein, a hybrid of H₂TiO₃/H₄Ti₅O₁₂ with rich phase boundaries is constructed via a facile one-step solid-state method. Owing to the different Fermi energy levels of the two phases, the electrons are transferred at the phase interface between H₂TiO₃ and H₄Ti₅O₁₂, developing an internal electric field (IEF). The built IEF provides an extra driving force to boost the solid-phase Li⁺ transport, hence enhancing the Li extraction kinetics. Threrfore, the H₂TiO₃/H₄Ti₅O₁₂ hybrid exhibits outstanding Li exchange performance of 42.43 and 20.50 mg g^-1 under alkaline and neutral conditions, corresponding to the hightest Li extraction rate of 5.30 and 2.05 mg g^-1 h^-1 reported so far. Our work offers an innovative strategy to promote the Li exchange performance of LIS especially under neutral conditions.

Chloride Adsorbates Enhance the Photocarrier Separation and Promote the Bio-Syngas Evolution

Photocarrier separation and migration to the surface are vital for photocatalysis. However, the mobility of the surface holes and electrons makes them easily recombine before participating in the surface reaction, which constrains the photocatalytic efficiency. Targeting this problem, herein, it is reported that chloride adsorbates enhance the photocarrier separation and promote the bio-syngas evolution. Chloride, adsorbed on the surface of CdS (CdS-Cl), can increase the internal electric field and enhance the charge separation and migration to the surface. Moreover, compared with pristine CdS where holes are mobile and distributed on all the surface atoms, CdSCl can reduce the hole mobility via delocalization on specific sites and thus prolong the photocarrier lifetime. This contributes to an 11-fold enhanced photocatalytic syngas evolution from glycerol. This study reports the pivotal effect of surface adsorbates on photocarrier separation and offers a convenient strategy to prohibit surface holes and electrons recombination for solar energy utilization.Chloride absorbates on CdS contribute to enhanced photocatalytic syngas evolution from glycerol by increasing the internal electric field.

The Precision Defect Engineering with Nonmetallic Element Refilling Strategy in g-C3 N4 for Enhanced Photocatalytic Hydrogen Production

Traditional defect engineering and doping strategies are considered effective means for improving H₂ evolution, but the uncontrollability of the modification process does not always lead to efficient activity. A defect-induced heteroatom refilling strategy is used here to synthesize heteroatoms introduced carbon nitride by precisely controlling the "introduction" sites on efficient N1 sites. Density functional theory calculations show that the refilling of B, P, and S sites have stronger H₂ O adsorption and dissociation capacity than traditional doping, which makes it an optimal H₂ production path. The large internal electric field strength of heteroatom-refilled catalysts leads to fast electron transfer and the hydrogen production of the best sample is up to 20.9 mmol g^-1  h^-1 . This work provides a reliable and clear insight into controlled defect engineering of photocatalysts and a universal modification strategy for typical heteroatom and co-catalyst systems for H₂ production.

Gradient Cationic Vacancies Enabling Inner-to-outer Tandem Homojunction: Strong local Internal Electric Field and Reformed basic sites Boosting CO2 Photoreduction

Slow charge dynamics and large activation energy of CO₂ severely hinder the efficiency of CO₂ photoreduction. Defect engineering is a well-established strategy, while the function of common zero-dimensional vacancy defect is always restricted to promoting surface adsorption. Here, we report that gradient tungsten vacancies layer with a thickness of 3∼4 nm is created across the Bi₂ WO₆ nanosheets by a post-etching approach. It enables formation of an inner-to-outer tandem homojunction with a strong internal electric field directing from outer to inner within the gradient vacancies layer, which provides a strong driving force for the migration of the photoelectron from the bulk to the surface of catalyst. Meanwhile, the introduction of gradient W vacancies changes the coordination environment around O and W atoms, leading to an alteration in the basic sites and the mode of CO₂ adsorption on the catalyst surface from weak/strong adsorption (O sites) to moderate adsorption (O and W sites), which ultimately decreases the formation barrier of key intermediate *COOH and facilitates the conversion thermodynamics for CO₂ . Without any cocatalysts and sacrificial reagents, W-vacant Bi₂ WO₆ shows an outstanding photocatalytic CO₂ reduction performance with a CO production rate of 30.62 μmol g^-1 h^-1 and a selectivity of 99%, being one of the best catalysts in similar reaction system. This study discloses that gradient vacancies as a new type of defect will show huge potential in regulating charge dynamics and catalytic reaction thermodynamics. This article is protected by copyright. All rights reserved.

Selective Potassium Deposition Enables Dendrite-Resistant Anodes for Ultrastable Potassium-Metal Batteries

Instability at the solid electrolyte interface (SEI) and uncontrollable growth of potassium dendrites have been pressing issues for potassium-ion batteries. Herein, a self-supporting electrode composed of bismuth and nitrogen-doped reduced graphene oxide (Bi₈₀ /NrGO) is designed as an anode host for potassium-metal batteries. Following the molten potassium diffusion into Bi₈₀ /NrGO, the resulting K@Bi₈₀ /NrGO exhibits unique hollow pores that provide K⁺ -diffusion channels and deposition space to buffer volume expansion, thus maintaining the electrode structure and SEI stability. The K@Bi₈₀ /NrGO also provides a controlled electric field that promotes uniform K⁺ flux, abundant potassiophilic N sites, and Bi alloying active sites, collectively enabling precise nucleation and selective deposition of potassium to achieve dendrite-resistant anodes. With the K@Bi₈₀ /NrGO-based optimized electrodes, the assembled K@Bi₈₀ /NrGO symmetrical cells can sustain stable cycling over 3000 h at a current density of 0.2 mA cm^-2 . Full cells with a Prussian blue cathode and K@Bi₈₀ /NrGO anode exhibit high stability (with no degradation for 1960 cycles at 1000 mA g^-1 ) with 99% Coulombic efficiency. This work may lead to the design of anodes with the triple attributes of precise nucleation, smooth diffusion, and dendrite inhibition, ideal for developing stable potassium-metal anodes and beyond.

Effects of Alternating Magnetic Fields on the OER of Heterogeneous Core-Shell Structured NiFe2O4@(Ni, Fe)S/P

Composition optimization, structural design, and introduction of external magnetic fields into the catalytic process can remarkably improve the oxygen evolution reaction (OER) performance of a catalyst. NiFe₂O₄@(Ni, Fe)S/P materials with a heterogeneous core-shell structure were prepared by the sulfide/phosphorus method based on spinel-structured NiFe₂O₄ nanomicrospheres. After the sulfide/phosphorus treatment, not only the intrinsic activity of the material and the active surface area were increased but also the charge transfer resistance was reduced due to the internal electric field. The overpotential of NiFe₂O₄@(Ni, Fe)P at 10 mA cm^-2 (iR correction), Tafel slope, and charge transfer resistance were 261 mV, 42 mV dec^-1, and 3.163 Ω, respectively. With an alternating magnetic field, the overpotential of NiFe₂O₄@(Ni, Fe)P at 10 mA cm^-2 (without iR correction) declined by 45.5% from 323 mV (0 mT) to 176 mV (4.320 mT). Such enhancement of performance is primarily accounted for the enrichment of the reactive ion OH^- on the electrode surface induced by the inductive electric potential derived from the Faraday induction effect of the AMF. This condition increased the electrode potential and thus the charge transfer rate on the one hand and weakened the diffusion of the active substance from the electrolyte to the electrode surface on the other hand. The OER process was dominantly controlled by the charge transfer process under low current conditions. A fast charge transfer rate boosted the OER performance of the catalyst. At high currents, diffusion exerted a significant effect on the OER process and low OH^- diffusion rates would lead to a decrease in the OER performance of the catalyst.

Interfacial Chemical Bond Engineering in a Direct Z-Scheme g-C3N4/MoS2 Heterojunction

The Z-scheme heterojunction shows great potential in photocatalysis due to its superior carrier separation efficiency and strong photoredox properties. However, how to regulate the charge separation at the nanometric interface of heterostructures still remains a challenge. Here, we take g-C₃N₄ and MoS₂ as models and design the Mo-N chemical bond, which connects exactly the CB of MoS₂ and VB of g-C₃N₄. Thus, the Mo-N bond could act as an atomic-level interfacial "bridge" that provides a direct migration path of charge carriers between g-C₃N₄ and MoS₂. Experiments confirmed that the Mo-N bond and the internal electric field promote greatly the photogenerated carrier separation. The optimized photocatalyst exhibits a high hydrogen evolution rate that is about 19.6 times that of the pristine bulk C₃N₄. This study demonstrates the key role of an atomic-level interfacial chemical bond design in heterojunctions and provides a new idea for the design of efficient catalytic heterojunctions.

Modulating Co-catalyst/Facet Junction for Enhanced Photoelectrochemical Water Splitting

Rational construction of electric field via assembling appropriate co-catalysts on anisotropic facets is of great significance for improving the photogenerated charge separation efficiency. However, this strategy usually gives rise to Fermi-level pinning which is not contributive to the charge separation but deleterious to the photoelectrochemical performance through consuming the measurable photovoltage. Herein, we demonstrate that manganese dioxide electrodeposited on the (111) facet of titanium dioxide nanorods could tremendously boost the catalytic activity of pristine photoanode via a stronger interface electric field and less photovoltage decay compared with the counterpart grown on the (110) facet. A photocurrent density of 1.65 mA·cm^-2 at 1.23 V (vs reversible hydrogen electrode), nearly the theoretical maximum of titanium dioxide, is achieved by the optimum photoanode with an extremely high separation efficiency of 95.15%. This study offers more in-depth insights into the design of carrier separation strategy through loading co-catalysts on different substrate surfaces for more efficient solar energy conversion.

Ferroelectricity and Schottky Heterojunction Engineering in AgNbO3: A Simultaneous Way of Boosting Piezo-photocatalytic Activity

As an efficient and economical way of dealing with organic pollutants, piezo-photocatalysis has attracted great interest. In this work, we demonstrated that ferroelectricity and Schottky heterojunction engineering could significantly enhance the piezo-photocatalytic activity of AgNbO₃. The poled 20 mol % K⁺ doped AgNbO₃ disclosed its superior piezo-photocatalytic activity of 0.131 min^-1 for 10 mg·L^-1 RhB, which is 7.8 times of the pristine one under the condition of illumination only. The designed piezo-photocatalyst also exhibited good piezo-photocatalytic stability after four cycles. These merits are attributed to the built-in electric field associated with the large spontaneous polarization and low coercive field originated from the stable ferroelectric state after ferroelectricity engineering, plus with the electron trapper effect of the in situ precipitated metal Ag particles. Our work not only provides a promising piezo-photocatalyst for degrading organic contaminants but also paves a good way for developing high piezo-photocatalytic activity catalysts.

Enhanced localized dipole of Pt-Au single-site catalyst for solar water splitting

Single-atom or single-site catalysts have received considerable research interest in photocatalysis and many other heterogeneous catalytic processes. However, the single metal sites did not obviously change the charge transportation process of the photocatalyst and thus hardly contributed to the enhancement of charge separation and transfer. Inspired by the synergy between metal species in classical catalytic reactions, this research presents a strategy of constructing a Pt-Au binary single-site catalyst. Pt-Au binary single sites not only functioned as the catalytic reactive sites but also modulated the charge distribution and enhanced the internal electric field. The concept and the strategy of this work are expected to provide a novel perspective for improving photocatalytic charge transportation dynamics.

Solar water splitting is regarded as holding great potential for clean fuels production. However, the efficiency of charge separation/transfer of photocatalysts is still too low for industrial application. This paper describes the synthesis of a Pt-Au binary single-site loaded g-C₃N₄ nanosheet photocatalyst inspired by the concept of the dipole. The existent larger charge imbalance greatly enhanced the localized molecular dipoles over adjacent Pt-Au sites in contrast to the unary counterparts. The superposition of molecular dipoles then further strengthened the internal electric field and thus promoted the charge transportation dynamics. In the modeling photocatalytic hydrogen evolution, the optimal Pt-Au binary site photocatalysts (0.25% loading) showed 4.9- and 2.3-fold enhancement of performance compared with their Pt and Au single-site counterparts, respectively. In addition, the reaction barrier over the Pt-Au binary sites was lowered, promoting the hydrogen evolution process. This work offers a valuable strategy for improving photocatalytic charge transportation dynamics by constructing polynary single sites.

Engineering an Interfacial Facet of S-Scheme Heterojunction for Improved Photocatalytic Hydrogen Evolution by Modulating the Internal Electric Field

Constructing a step-scheme (S-scheme) heterojunction represents a promising route to overcome the drawbacks of single-component and traditional heterostructured photocatalysts by simultaneously broadening the optical response range and optimizing the redox ability of the photocatalytic system, the efficiency of which greatly lies in the separation behaviors of photogenerated charge carriers with strong redox capabilities. Herein, we demonstrate interfacial facet engineering as an effective strategy to manipulate the charge transfer and separation for substantially improving the photocatalytic activities of S-scheme heterojunctions. The facet engineering is performed with the growth of ZnIn₂S₄ on (010) and (001) facet-dominated BiOBr nanosheets to fabricate ZIS/BOB-(010) and ZIS/BOB-(001) S-scheme heterojunctions, respectively. It is disclosed that a larger Fermi level difference between BiOBr-(001) and ZnIn₂S₄ enables the formation of a stronger built-in electric field with more serious band bending in the space charge region around the interface. As a result, the directional migration and recombination of pointless photoexcited electrons in the conduction band (CB) of BiOBr and holes in the valence band (VB) of ZnIn₂S₄ with weak redox ability are speeded up enormously, thereby contributing to more efficient spatial separation of powerful CB electrons of ZnIn₂S₄ and VB holes of BiOBr for participating in overall redox reactions. Profiting from these merits, the ZIS/BOB-(001) displays a significant superiority in photocatalytic H₂ evolution over ZIS/BOB-(010) and mono-component counterparts. This work provides new deep insights into the rational construction of a S-scheme photocatalyst based on an interfacial facet design from the viewpoint of internal electric field regulation.

Layer Edge States Stabilized by Internal Electric Fields in Two-Dimensional Hybrid Perovskites

Two-dimensional (2D) organic-inorganic hybrid perovskites have been intensively explored in recent years due to their tunable band gaps and exciton binding energies and increased stability with respect to three-dimensional (3D) hybrid perovskites. Experimental observations suggest the existence of localized edge states in 2D hybrid perovskites which facilitate extremely efficient electron-hole dissociation and long carrier lifetimes, while multiple origins for their formation have been proposed. Using first-principles calculations, we demonstrate that layer edge states are stabilized by internal electric fields created by polarized molecular alignment of organic cations in 2D hybrid perovskites when they are two layers or thicker. Our study gives a simple physical explanation of the edge state formation, and facilitating the design and manipulation of layer edge states for optoelectronic applications.

Bimetal-organic Framework-derived Co9 S8 /ZnS@NC Heterostructures for Superior Lithium-ion Storage

Heterostructure engineering of electrode materials, which is expected to accelerate the ion/electron transport rates driven by a built-in internal electric field at the heterointerface, offers unprecedented promise in improving their cycling stability and rate performance. Herein, carbon nanotubes with Co₉ S₈ /ZnS heterostructures embedded in a N-doped carbon framework (Co₉ S₈ /ZnS@NC) have been rationally designed via an in-situ vapor chemical transformation strategy with the aid of thiophene, which not only acted as carbon source for the growth of carbon nanotubes but also as sulfur source for the sulfurization of metal Zn and Co. Density functional theory (DFT) calculation shows an about 3.24 eV electrostatic potential difference between ZnS and Co₉ S₈ , which results in a strong electrostatic field across the interface that makes electrons transfer from Co₉ S₈ to the ZnS side. As expected, a stable cycling performance with reversible capacity of 411.2 mAh g^-1 at 1000 mA g^-1 after 300 cycles, excellent rate capability (324 mAh g^-1 at 2000 A g^-1 ) and a high percentage of pseudocapacitance contribution (87.5% at 2.2 mv/s) for lithium-ion batteries (LIBs) are achieved. This work provides a possible strategy for designing multicomponent heterostructural materials for application in energy storage and conversion fields.

Stability and Sensing Enhancement by Nanocubic CeO2 with {100} Polar Facets on Graphene for NO2 at Room Temperature

Metal oxides with a polar surface interact strongly with polar NO₂ molecules, thus facilitating sensitive detection of NO₂. In this work, the composites comprising graphene and cubic CeO₂ nanoparticles with the {100} polar surface are prepared by a hydrothermal technique, and they exhibit fast response, excellent selectivity, stable recovery, and sensitive detection with a low detection limitation of 1 ppm for NO₂ at room temperature. According to the first-principle calculations, the adsorption energy of NO₂ on the CeO₂{100} polar surface is the most negative corresponding to the strongest interactions between them. The formation energy of oxygen vacancies (O_v) on the {100} polar plane is also negative, and the abundant O_v facilitates the adsorption of NO₂. The internal electric field near the polar surface promotes the charge separation and accelerates the charge exchange between NO₂ and the composites. In addition, graphene promotes electron transfer at the interface and improves the stability of the CeO₂{100} polar surface. The composites of graphene and metal oxides with a polar surface are excellent for NO₂ detection, and the discovery reveals a new sensing strategy.

Ferroelectric Polarization-Enhanced Photocatalysis in BaTiO3-TiO2 Core-Shell Heterostructures

Suppressing charge recombination and improving carrier transport are key challenges for the enhancement of photocatalytic activity of heterostructured photocatalysts. Here, we report a ferroelectric polarization-enhanced photocatalysis on the basis of BaTiO₃-TiO₂ core-shell heterostructures synthesized via a hydrothermal process. With an optimal weight ratio of BaTiO₃ to TiO₂, the heterostructures exhibited the maximum photocatalytic performance of 1.8 times higher than pure TiO₂ nanoparticles_. The enhanced photocatalytic activity is attributed to the promotion of charge separation and transport based on the internal electric field originating from the spontaneous polarization of ferroelectric BaTiO_3. High stability of polarization-enhanced photocatalysis is also confirmed from the BaTiO₃-TiO₂ core-shell heterostructures. This study provides evidence that ferroelectric polarization holds great promise for improving the performance of heterostructured photocatalysts.

Enhanced ferro-photocatalytic performance for ANbO3 (A = Na, K) nanoparticles

In this study, NaNbO₃ with average grain size of ~50 nm and KNbO₃ with average grain size of ~300 nm nanocrystals are prepared by the water-based citrate precursor sol-gel process. However, the KNbO₃ sample exhibits better photocatalytic performance than that of the NaNbO₃ sample by Rh B degradation experiment. By Rietveld refinements and piezoelectric displacement measurements, the KNbO₃ with the space group of Bmm2 is ferroelectric while the NaNbO₃ with the space group of Pbma is antiferroelectric. The polarization-modulated built-in electric fields in the ferroelectric KNbO₃ nanoparticles can efficiently enhance the separation of photo-generated charge carries and thus improve the photocatalytic activity. However, there is no internal electric field in the antiferroelectric grain because of the antiparallel spontaneous polarization in the adjacent unit cell. Therefore, KNbO₃ exhibits better oxidizing ability of organic dyes than NaNbO₃. The ferroelectric KNbO₃ nanoparticles exhibit an optimum photocatalytic performance for a complete degradation of Rh B in 100 min under UV-Vis light irradiation with auxiliary ultrasonic excitation. This study demonstrates that the perovskite-type ferroelectric nanocrystals are potentially to design high-performance catalysts for degradation of contaminant.

Giant Enhancement of Internal Electric Field Boosting Bulk Charge Separation for Photocatalysis

Incorporating carbon into Bi3 O4 Cl enhances its internal electric field by 126 times, which induces a bulk charge separation efficiency (ηbulk ) of 80%. This ultrahigh ηbulk value presents a state-of-the-art result in tuning the bulk charge separation. The generated C-doped Bi3 O4 Cl has a noble-metal- and electron-scavenger-free water-oxidation ability under visible light, which is difficult to achieve with most existing photocatalysts.