Accelerated Charge Transfer Research Articles

Study on interface engineering and chemical bonding of the ReS2@ZnO heterointerface for efficient charge transfer and nonlinear optical conversion efficiency.

Rhenium sulfide (ReS2) has emerged as a promising two-dimensional material, demonstrating broad-spectrum visible absorption properties that make it highly relevant for diverse optoelectronic applications. Manipulating and optimizing the pathway of photogenerated carriers play a pivotal role in enhancing the efficiency of charge separation and transfer in novel semiconductor composites. This study focuses on the strategic construction of a semiconductor heterostructure by synthesizing ZnO on vacancy-containing ReS2 (VRe-ReS2) through chemical bonding processes. The ingeniously engineered built-in electric field within the heterostructure effectively suppresses the recombination of photogenerated electron-hole pairs. A direct and well-established interfacial connection between VRe-ReS2 and ZnO is achieved through a robust Zn-S bond. This distinctive bond configuration leads to enhanced nonlinear optical conversion efficiency, attributed to shortened carrier migration distances and accelerated charge transfer rates. Furthermore, theoretical calculations unveil the superior chemical interactions between Re vacancies and sulfide moieties, facilitating the formation of Zn-S bonds. The photoluminescence (PL) intensity is increased by the formation of VRe-ReS2 and ZnO heterostructure and the PL quantum yield of VRe-ReS2 is improved. The intricate impact of the Zn-S bond on the nonlinear absorption behavior of the VRe-ReS2@ZnO heterostructure is systematically investigated using femtosecond Z-scan techniques. The charge transfer from ZnO to ReS2 defect levels induces a transition from saturable absorption to reverse saturable absorption in the VRe-ReS2@ZnO heterostructure. Transient absorption measurements further confirm the presence of the Zn-S bond between the interfaces, as evidenced by the prolonged relaxation time (τ3) in the VRe-ReS2@ZnO heterostructure. This study offers valuable insights into the rational construction of heterojunctions through tailored interfacial bonding and surface/interface charge transfer pathways. These endeavors facilitate the modulation of electron transfer dynamics, ultimately yielding superior nonlinear optical conversion efficiency and effective charge regulation in optoelectronic functional materials.

Single-atom sites regulation by the second-shell doping for efficient electrochemical CO2 reduction

Nitrogen-doped carbon loaded single-atom catalysts (SACs) are promising candidates for electrocatalytic conversion of CO2 into high-valuable chemicals, and the modification of catalysts by heteroatom-doping strategy is an effective approach to enhance the CO2 reduction performance. However, the large difference exists in atomic radius between nitrogen atoms and the doped heteroatoms may lead to the poor stability of active sites. In this study, we have synthesized a Ni single atom catalyst with S doping at the second-shell on the ultrathin carbon nanosheets support (Ni-N4-SC) by solid-phase pyrolysis. The S atom in the second-shell contributes to the higher efficiency of CO2 conversion at lower potentials while the Ni-N4-SC can be more stable. The experimental results and theoretical calculations indicate that the S atom in second-shell breaks the uniform charge distribution and reduces the free energy of hydrogenation, which can increase the adsorption of CO2, accelerate charge transfer, and reduce the reaction energy barrier. This work reveals the close relationship between the second-shell and the electrocatalytic activity of single atom sites, which also provides a new perspective to design efficient single atom catalysts.

Regulating composition of Mn-CeOx nanoparticles with ultra-small sizes on Al2O3 for enhanced catalytic ozonation

Herein, Al2O3 supported ultra-small Mn-CeOx nanoparticles (Mn-CeOx/Al2O3) are prepared by a facile impregnation method for removal of phenolic compounds via catalytic ozonation. Mn and Ce species are in the form of polyvalent oxide nanoparticles with an average size of 0.9 nm. The removal efficiency of total organic carbon for phenol-containing model wastewater by Mn-CeOx/Al2O3 shows a volcano relationship by changing the mass ratio of Mn and Ce, and reaches up to the peak value when the mass ratio is 5:5. The cycle stability tests suggest the removal efficiency of Mn-CeOx/Al2O3 could maintain at 90.16 % after 5 circles. The enhanced performance should be attributed to the optimized magnetism and accelerated charge transfer by composition regulation. The magnetic strength changing affects the adsorption mode of O3, while the redox cycle of Mn(IV)/Mn(III) and Ce(IV)/Ce(III) could enhance the activation of O3 to produce more ·OH and 1O2 for the organic molecules mineralization.

Amorphous high entropy oxides based on polyoxometalate clusters to accelerate surface reconstruction for oxygen evolution reaction

High-entropy materials (HEMs) with unique electronic structures and diverse elemental compositions have emerged, however, HEMs are complicated to prepare. Here, we prepared an amorphous FeCoNiMoW high-entropy oxide (FCNMWO) catalyst by simple one-pot hydrothermal preparation, based on a method that used polyoxometalate clusters as metal cation linkers. The FCNMWO with amorphous structure exhibited better oxygen evolution reaction, as confirmed by a series of characterization and electrochemical experiments, which exhibited a low overpotential of 313 mV at a current density of 10 mA cm−2 with a Tafel slope of 40.95 mV dec−1, indicating excellent charge transfer capability. Moreover, the presence of polyoxometalate clusters modulated the electronic structure and accelerated charge transfer processes, promoting OER property. In addition, analysis of the results before and after OER stability revealed that the leaching of Mo induced reconstruction on the catalyst surface, and the MOOH were actual active species. This work is instructive for further design and development of efficient high entropy electrocatalysts with admirable OER properties.

Branch-leaf structural VS2@C/TiO2 anode for high-performance lithium-ion batteries

Heterogeneous materials combine the advantage of each component through the synergy effect to become promising electrode materials for lithium-ion batteries (LIBs). Designing heterojunctions with specific structures can better show their electrochemical performance. In this work, we fabricated VS2 nanosheets perpendicular to the C/TiO2 nanotube (VS2@C/TiO2) composite with a “branch-leaf” structure by an electrospinning-carbonization-solvothermal method. Notably, the interior of the C/TiO2 nanotube consists of small-sized TiO2 nanoparticles, which guarantees high electrochemical reactivity. The presence of carbon not only accelerates charge transfer across the interface of carbon-TiO2 but also serves as an anchor for the growth of VS2 nanosheet by CSV bonding, thus enhancing the structural stability of the electrode. As anode for LIBs, the VS2@C/TiO2 electrode exhibits a high reversible capacity of 748 mAh g−1 and 324.2 mAh g−1 at 100 mA g−1 and 1 A g−1, respectively. This work highlights the unique “branch-leaf” design of VS2@C/TiO2, which offers a new prospect for developing high-performance heterogeneous electrodes for LIBs.

Highly Stable and Active Ru Clusters Supported on Boron Carbon Nitride for Acidic Water Oxidation

In recent years, metal oxides, such as IrO2, have been widely used in proton exchange membrane water electrolysis (PEMWE) because of their excellent catalytic activity and long-term stability [1]. However the high price and scarcity of these catalysts were not enough to meet the requirements of PEMWE [2]. Therefore, it is significant to explore novel electrochemically active, stable, and low-cost catalysts.In this paper, a uniformly dispersed Ru confined on boron carbon nitride support was synthesized and studied. The surface chemical states of Ru were tuned by the interaction between Ru and the active N in boron carbon nitrogen (BCN), forming a highly stable Ru-N bond. Benefiting from a graphene-like structure, the BCN-0.5Ru catalyst exhibited greater conductivity than RuO2. The strong interaction between Ru and the BCN support also allowed for accelerated charge transfer at the electrode interface.Transmission electron microscopy (TEM) investigations revealed that Ru clusters were uniformly dispersed on BCN (Figure 1a), and the particle size distributions (Figure 1b) showed that the Ru clusters possessed an average particle size of 4 nm. It suggests that the Ru nanoclusters on the BCN support had small particle sizes and a narrow particle size distribution. These results demonstrated that the BCN support helped disperse the Ru metal nanoclusters more homogeneously than what occurred when RuO2 was prepared via direct RuCl3 annealing. The electrochemical performance of oxygen evolution reaction (OER) for BCN-xRu catalysts in O2-saturated 0.5 M H2SO4 solution was evaluated. The BCN-0.5Ru catalyst demonstrates a low overpotential of 164 mV at a current density of 10 mA cm–2 and remains stable for 12 h in acidic electrolyte (Figure 1c). In contrast, RuO2 without any support fails in only 1 h (Figure 1c). We propose that the surface chemical states of Ru supported by BCN may play an important role in enhancing stability. This study provides insights into designing and synthesizing high-performance electrocatalysts for acidic OER.

Nicop Anchored Porous Ti3C2tx Support with 3D Interconnected Structure for Advanced Hydrogen Evolution Reaction Electrocatalysts

MXene have gained much attention as promising electrocatalysts for noble metal-free hydrogen evolutrion reaction (HER) electrocatalysts owing to their high electrical conductivity, hydrophilic surfaces, abundant functional groups, and rational design for hybridization with other materials. In this study, a novel porous monolayered-Ti3C2TX@NiCoP (P-Ti3C2Tx@NiCoP) nanostructure was developed with 3D interconnected structure to significantly improve charge transfer capability and electrocatalytic activity. A strategic approach of modifying pristine Ti3C2Tx monolayers and combining them with other active cocatalysts. Specifically, the H2O2-utilized oxidation and HF etching process formed a highly microporous structure with a maximized surface area of monolayered MXenes as the support. A subsequent solvothermal process followed by phosphidation enabled successful anchoring of highly HER-active NiCoP nanoclusters onto abundantly exposed terminal edges of the P-Ti3C2Tx support. The structural porosity of the P-Ti3C2Tx nanoflakes played an important role in creating additional room for embedding catalytically active species while stably imparting high electrical conductivity to accelerate charge transfer to NiCoP nanoclusters. Moreover, inspired by the pH dependent change of structural arrangement of the Ti3C2Tx, we successfully induced 3D-interconnetecd structure by modulating surface electrostatic forces among Ti3C2Tx monolayers. Of note, the 3D-interconnected structure would shift charge transfer behavior from intermolecular to intramolecular aspects and this would contribute to enhanced charge transfer kinetics. With structural modification of support material and effective hybridization of active species, P-Ti3C2Tx@NiCoP showed highly enhanced HER activity with significantly lower overpoential of 115 and 101 mV at a current density of -10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH, respectively, along with showing long-term stability over 60 h. As such, our approach of designing structurally modified-Ti3C2Tx and hybridization with other electrocatalytically active species would function as a solid platform for implementing Ti3C2Tx-based hetero-nanostructures to achieve state-of-the-art performance in next-generation energy conversion applications.

Interlayer and Phase Engineering Modifications of K-MoS2@C Nanoflowers for High-Performance Degradable Zn-Ion Batteries.

2D transition metal dichalcogenides (TMDs) have garnered significant interest as cathode materials for aqueous zinc-ion batteries (AZIBs) due to their open transport channels and abundant Zn2+ intercalation sites. However, unmodified TMDs exhibit low electrochemical activity and poor kinetics owing to the high binding energy and large hydration radius of divalent Zn2+. To overcome these limitations, an interlayer engineering strategy is proposed where K+ is preintercalated into K-MoS2 nanosheets, which then undergo in situ growth on carbon nanospheres (denoted as K-MoS2@C nanoflowers). This strategy stimulates in-plane redox-active sites, expands the interlayer spacing (from 6.16 to 9.42 Å), and induces the formation of abundant MoS2 1T-phase. The K-MoS2@C cathode demonstrates excellent redox activity and fast kinetics, attributed to the potassium ions acting as a structural "stabilizer" and an electrostatic interaction "shield," accelerating charge transfer, promoting Zn2+ diffusion, and ensuring structural stability. Meanwhile, the carbon nanospheres serve as a 3D conductive network for Zn2+ and enhance the cathode's hydrophilicity. More significantly, the outstanding electrochemical performance of K-MoS2@C, along with its superior biocompatibility and degradability of its related components, can enable an implantable energy supply, providing novel opportunities for the application of transient electronics.

Synergistic effect of oxygen vacancies and doped sulfur over BiOBr for efficient visible photocatalytic removal of dyes

Herein, the BiOBr co-modified with oxygen vacancies (Vo) and doped by sulfur was a promising photocatalyst (Vo-BiOBr-S), which was synthesized by a one-pot solvothermal approach. The TEM showed that Vo-BiOBr-S is a sea urchin-shaped microsphere with a diameter of about 4 μm. The photocatalytic efficiency of Vo-BiOBr-S was studied by removing rhodamine B and methylene blue, which were higher than that of BiOBr, Vo-BiOBr and BiOBr-0.8S, respectively. Additionally, the photocatalyst exhibits high degradation of aqueous solutions containing both rhodamine B and methylene blue. The photocurrent and photoluminescence tests showed that the improved photocatalytic performance of Vo-BiOBr-S was due to the accelerated charge transfer and separation by the internal electric field, which extended the visible light absorption range. Furthermore, experiments free radical trapping revealed that superoxide radicals were the principal active species in this system, contributing to the superior degradation performance of Vo-BiOBr-S. The density of states of the samples was calculated via DFT to analyse the energy band structure. The effectiveness of Vo-BiOBr-S in mineralising RhB under LED light was demonstrated through total organic carbon tests. This study presents a method to design efficient photocatalysts for use in environmental preservation.

Enhancing performance of triboelectric nanogenerator by accelerating the charge transfer strategy

Developing high-performance triboelectric nanogenerators (HP-TENGs) is paramount for expanding their commercial utility. Presently, HP-TENGs predominantly concentrate on augmenting surface charge density. Here, we introduce an innovative strategy, denoted ACT-TENG (Accelerated Charge Transfer TENG), which markedly enhances TENG's performance by effectively accelerating charge transfer between materials, all while preserving the original charge density. We substantiate the feasibility of this approach through systematic investigations, employing magnetic field modulation and bidirectional rotation mode to verify the gain effect of ACT-TENG. Notably, compared to conventional free-standing TENG (FS-TENG), ACT-TENG achieves a 4-fold increase in charge transfer rate and a remarkable 14.6-fold enhancement in output power. This leads to an impressive average power density of 499.05 mW m-² Hz-¹ , showcasing superior performance compared to previously reported FS-TENG designs. Furthermore, ACT-TENG exhibits exceptional characteristics when deployed in a water flow environment, generating the power of 10.76 mW at a flow rate of 180 L min−1. Finally, we utilize ACT-TENG to harvest energy from water flow, constructing a self-powered Internet of Things (IoT) system within the underground pipeline gallery. This study addresses existing limitations in TENG technology and offers valuable insights into further advancements in enhancing TENG's performance.

Effect of biaxial strain and vacancy defects in 2D MoS2 monolayer for the sensing of nitrobenzene: A DFT investigation

Considering the increased release of toxic nitrobenzene (NB) molecules into the atmosphere, proposing a sensor material that could effectively remove it from the environment is essential. In this regard, we have investigated the NB adsorption performance of vacancy-defected (S, Mo and di S) and biaxially strained (−4 % to 4 %) MoS2 monolayers through density functional theory (DFT) simulations. Applying biaxial (tensile and compression) strain to the monolayer significantly increased the adsorption energy and charge transfer to −1.02 eV and 0.09 e, respectively, much greater than in the pristine case. The formation energy calculations verified the stability of (S, Mo, 2S) vacancy-defected MoS2 monolayer. The low formation energy of 3.3 eV suggests the ease of formation of MoS2 monolayer with single S vacancy. Introducing defects and strain improved the conductivity of the monolayer, thereby increasing the NB adsorption ability. The reasonable NB adsorption energy on the modified monolayer was due to the accelerated charge transfer and orbital interaction between the valence S 3p orbitals of MoS2 and 2p orbitals of O in NB. The recovery time of the strained and defective monolayers is the order of only a few seconds at 400 K, which is quite attainable. Therefore, this work put forth a more effective to improve the NB performance of the monolayer and can be a motivation for the further development of high-performance biomolecule sensors.

Optimizing water electrolysis activity in Mo-doped Sr2FeCoO6-δ perovskites by balancing oxygen vacancies and structural stability

Perovskite-based solid oxide electrolysis cells (SOECs) are promising for efficacious hydrogen production. This work explored how varying molybdenum (Mo) content impacts the structure and performance of Sr2FeCo1-xMoxO6-δ (SFCMx) perovskites for SOEC water electrolysis. SFCMx (x = 0.1–0.5) were synthesized via sol-gel method and incorporated into symmetrical cells. Electrolysis testing showed SFCM0.3 had the highest activity, achieving 2.09 A cm−2 at 2.0 V and 800 °C, compared to 0.964 and 0.847 A cm−2 for SFCM0.1 and SFCM0.5 respectively. This optimal performance with 0.3 Mo doping was put down to simultaneous variations in oxygen vacancy concentration and crystalline structure stability. Lower Mo doping accelerated charge transfer but destabilized the structure, while higher doping stabilized the cubic perovskite structure but reduced vacancies and electrocatalytic activity. This work demonstrates that balancing activity and stability by optimizing dopant concentration is critical to maximize SOEC performance. This provides new insights for enhancing water electrolysis through controlled doping and tuning of the perovskite structure.

Decoration of Ag/Bi nanoparticles over brown TiO2-x/AgBiO3 nanocomposites: QDs-sized photocatalysts for impressive mitigation of water pollutants

Heterogeneous photocatalysis is a hot-spot research field for energy conversion and water detoxification. One of the most important challenges of photocatalysis is the designing and development of efficacious visible-light-triggered photocatalysts. In this regard, perovskite AgBiO3 and Ag/Bi elemental nanoparticles were decorated on brown TiO2−x via a facile procedure. Electron microscopy, XPS, and XRD studies provided strong evidence about developing TiO2−x/Ag/AgBiO3/Bi photocatalysts with quantum dot size of about 5.5 nm, and intimate contact among the counterparts. The TiO2−x/Ag/AgBiO3/Bi photocatalysts displayed boosted ability in the detoxification of tetracycline (TC), amoxicillin (AMX), fuchsine (FS), and methylene orange (MO) pollutants. The degradation rate constants of TC, AMX, FS, and MO over the optimum TiO2−x/Ag/AgBiO3/Bi photocatalyst were 25.9, 3.40, 5.70, and 1.92 folds greater than TiO2−x and 20.3, 12.3, 6.77, and 2.33 times larger than Ag/AgBiO3/Bi, respectively. Photoluminescence spectroscopy, EIS experiments, and Bode plots showed accelerated charge transfer and significant reduction of charges recombination within TiO2−x/Ag/AgBiO3/Bi nanocomposites. The recycling studies showed that the plasmonic photocatalyst retained the most activity after four times of utilization. Ultimately, an s-scheme charges segregation route was suggested for the boosted activity of the plasmonic TiO2−x/Ag/AgBiO3/Bi photocatalysts.

Defects-Induced Single-Atom Anchoring on Metal-Organic Frameworks for High-Efficiency Photocatalytic Nitrogen Reduction.

Aiming to improve the photocatalytic activity in N2 fixation to produce ammonia, herein, we proposed a photochemical strategy to fabricate defects, and further deposition of Ru single atoms onto UiO-66 (Zr) framework. Electron-metal-support interactions (EMSI) were built between Ru single atoms and the support via a covalently bonding. EMSI were capable of accelerating charge transfer between Ru SAs and UiO-66, which was favorable for highly-efficiently photocatalytic activity. The photocatalytic production rate of ammonia improved from 4.57 μmol g-1 h-1 to 16.28 μmol g-1 h-1 with the fabrication of defects onto UiO-66, and further to 53.28 μmol g-1 h-1 with Ru-single atoms loading. From the DFT results, it was found that d-orbital electrons of Ru were donated to N2 π✶-antibonding orbital, facilitating the activation of the N≡N triple bond. A distal reaction pathway was probably occurred for the photocatalytic N2 reduction to ammonia on Ru1 /d-UiO-66 (single Ru sites decorated onto the nodes of defective UiO-66), and the first step of hydrogenation of N2 was the reaction determination step. This work shed a light on improving the photocatalytic activity via feasibly anchoring single atoms on MOF, and provided more evidences to understand the reaction mechanism in photocatalytic reduction of N2 .

Defects‐Induced Single‐Atom Anchoring on Metal–Organic Frameworks for High‐Efficiency Photocatalytic Nitrogen Reduction

AbstractAiming to improve the photocatalytic activity in N2 fixation to produce ammonia, herein, we proposed a photochemical strategy to fabricate defects, and further deposition of Ru single atoms onto UiO‐66 (Zr) framework. Electron‐metal‐support interactions (EMSI) were built between Ru single atoms and the support via a covalently bonding. EMSI were capable of accelerating charge transfer between Ru SAs and UiO‐66, which was favorable for highly‐efficiently photocatalytic activity. The photocatalytic production rate of ammonia improved from 4.57 μmol g−1 h−1 to 16.28 μmol g−1 h−1 with the fabrication of defects onto UiO‐66, and further to 53.28 μmol g−1 h−1 with Ru‐single atoms loading. From the DFT results, it was found that d‐orbital electrons of Ru were donated to N2 π✶‐antibonding orbital, facilitating the activation of the N≡N triple bond. A distal reaction pathway was probably occurred for the photocatalytic N2 reduction to ammonia on Ru1/d‐UiO‐66 (single Ru sites decorated onto the nodes of defective UiO‐66), and the first step of hydrogenation of N2 was the reaction determination step. This work shed a light on improving the photocatalytic activity via feasibly anchoring single atoms on MOF, and provided more evidences to understand the reaction mechanism in photocatalytic reduction of N2.

2D semiconductor nanosheets for solar photocatalysis

AbstractIn the advancing world of graphene, highly anisotropic 2D semiconductor nanosheets, notable for their nanometer‐scale thickness, have emerged as a leading innovation, displaying immense potential in the exploration of renewable and clean energy production. These have garnered significant attention from researchers. The nanosheets are marked by their extraordinary electronic, optical, and chemical attributes, positioning them as attractive foundational components for heterogeneous photocatalysts. This review diligently summarizes both the seminal work and ongoing developments pertaining to 2D semiconductor nanosheets and their application to solar energy within the context of heterogeneous photocatalysis. We begin by detailing the distinctive properties of 2D semiconductor nanosheets, concentrating on their pivotal roles in augmenting photocatalytic efficiency, and explaining the intrinsic mechanisms that govern the migration rate of photogenerated carriers on the material's surface. Subsequently, we delineate the methods employed to synthesize typical 2D semiconductor nanosheets. In alignment with the overarching objective of expanding light absorption capacity and accelerating charge transfer, we also examine the current research on the hybridization techniques involving 2D materials of varied dimensions, as well as their deployment in diverse photocatalytic applications. We conclude by identifying promising avenues and potential challenges that await further exploration in this burgeoning field.

Fabrication of NiSx/MoS2 interface for accelerated charge transfer with greatly improved electrocatalytic activity in nitrogen reduction to produce ammonia

Electrocatalytic reduction of dinitrogen to produce ammonia at ambient conditions has increasingly attracted attentions. Molybdenum sulfide (MoS2) exhibits promises in electrocatalysis. However, the lack of reactive sites significantly limited the electrocatalytic activity of MoS2 when applied in the reduction of N2 to produce ammonia. Herein, we successfully prepared a NiSx/MoS2 heterostructural composite with abundant interfaces exposed. Moreover, the presence of metallic phase 1T-MoS2 provided better conductivity and more active sites. Benefited from this interface design, as-prepared NiSx/MoS2 composites exhibited excellent electrocatalytic activity in reduction of N2. The ammonia yield rate reached as high as 68.78 µg h−1 mg−1cat. at −0.60 V (vs. RHE) with a Faradic efficiency of 48.53 % at −0.50 V (vs. RHE), as well as charming selectivity and long-term stability. The density functional theory (DFT) calculation results indicated that the heterointerface formed between NiSx/MoS2 composites facilitated electrons transfer. And the adsorption of N2 on the Mo site is more stable, which synergistically improves the NRR performance. This work provides new evidences of constructing heterojunction materials to accelerate electron transfer between interfaces for highly efficient electrocatalytic nitrogen reduction.

Construction of an S-scheme Ce/Ti-MOFs heterojunction with abundant Oxygen vacancies (Ovs) for efficient charges separation: Performance and mechanism insight

The S-scheme heterojunction in the semiconductors can effectively enhance the photocatalytic activity by retaining strong light-generated electrons (e−) and holes (h+) while recombining meaningless charge carriers. In this work, a Ce/Ti-MOFs (CT-MOFs) heterojunction material with plentiful oxygen vacancies (Ovs) was synthesized via the hydrothermal method. The catalysts were employed for the degradation of Tetracycline (TC) in the aquatic environment under simulated sunlight. The Ce/Ti-MOFs (CT 1–4) sample exhibited the best photocatalytic activity, with a rate constant of 0.01243 min−1, which is 7.49 times greater than that of Ce-MOF, and 2.40 times higher than that of MIL-125 (Ti), respectively. The experimental results show that the constructed CT-MOFs can increase the density of Ovs, accelerate charge transfer, and improve photocatalytic performance. Furthermore, the Ti4+/Ti3+ variable valence metal cycle in CT 1–4 compensates for charge balance and promotes rapid carrier separation. The difference between the Fermi energy level and work function drives the electron transfer from the MIL-125(Ti) side to the Ce-MOF side. The above results indicate that the successful establishment of the S-scheme heterojunction preserves the strong redox effects of e− and h+, prolongs the electron lifetime, and facilitates the carrier's separation.

Interface engineering and oxygen vacancy of hollow/porous Co–CoO heterojunction nanoframes for high-activity electrocatalysis overall water splitting

Cobalt-based oxides are regarded as promising electrocatalysts in the field of overall water splitting ascribed to superior activity and desirable stability. Nevertheless, the poor electrical conductivity and insufficient active centers limit their development seriously. Herein, the hollow/porous Co–CoO nanoframes (denoted as Co–CoO NFs) with heterojunction and abundant oxygen vacancies have been constructed via continuous calcination and in-situ reduction strategies. Furthermore, the influence of heterostructure and oxygen vacancy on electrocatalytic activity is investigated systematically. The heterojunction interface formed by Co and CoO could expose more active sites and accelerate charge transfer. Besides, oxygen vacancy could regulate electronic structure, lowering the intermediate binding energy and reducing charge transfer impedance. Furthermore, the hollow/porous structure could increase the accessible internal and external surface area. As a result, Co–CoO-400 NFs exhibit prominent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) behavior, achieving the current density of −10 mA cm−2 and 10 mA cm−2 with the low overpotential of 103.0 and 276.0 mV, respectively, and the voltage required for overall water splitting is 1.54 V, surpassing the most reported Co-based electrocatalysts recently. Overall, this work provides an intellection and vision for designing dual-function electrocatalysts with controllable morphology, low energy consumption, and high activity, making a significant contribution for solving the future energy crisis.

Engineering nanoscale Ni3Se4/CoSe2/NC heterostructures with rigid construction for sodium ion storage

Engineering transition bimetallic selenide heterostructures could effectively accelerate charge transfer and promote reaction kinetics for the anode materials in sodium ion batteries. Especially, the nanoscale heterointerfaces with abundant grain boundaries could provide tremendous active sizes with enhanced capacity. However, constructing homogeneous nanoscale heterostructures with rigid framework upon cycling remains a huge challenge because of the severe cracking and aggregation of the nanoscale heterostructures during cycling. In this regard, nanoscale Ni3Se4/CoSe2 heterostructures within the nitrogen doped carbon networks (denoted as Ni3Se4/CoSe2/NC) is rationally designed in this work. The nitrogen doped carbon greatly boosts the electronic conductivity and effectively mitigates the agglomeration and volumetric alteration of Ni3Se4/CoSe2, thereafter guaranteeing the structural stability of heterostructured Ni3Se4/CoSe2 nanoparticles. As a proof-of-concept, the electrochemical behavior of the Ni3Se4/CoSe2/NC is largely improved, when compared with bare Ni3Se4/CoSe2 and carbon-encapsulated Ni3Se4/CoSe2 (Ni3Se4/CoSe2@NC). DFT calculations confirms the built-in electric field in the interface of Ni3Se4/CoSe2 which enhances charge carrier transport and promoting reaction kinetics. As expected, the Ni3Se4/CoSe2/NC exhibits the most excellent performance in SIBs, providing a high reversible capacity of 605.7 mA h g−1 at 0.1 A g−1 and 205 mA h g−1 at 5 A g−1.