Bifunctional Activity Research Articles

Electrocatalytic properties of transition metal vanadates (T = Ti, Cr, Mn, & Fe) for overall water splitting

In this work, first row transition metal vanadates (TMVs), including titanium vanadate (TiV), chromium vanadate (CrV), manganese vanadate (MnV), and iron vanadate (FeV), were synthesized and investigated their electrocatalytic performance for the alkaline water splitting. The prepared TMVs showed easy electron transfer characteristics and tunable band structures, and among these TMVs, the synthesized FeV demonstrated the best electrocatalytic bifunctional activities for both HER (η100 = 375 mV) and OER (η100 = 260 mV) with a significant electronic and morphological stability over 100 h operation. The examination of electronic structure revealed that the balanced catalyst-intermediate interaction through optimum d-p orbital hybridization in FeV, adhering to the Sabater principle, vouched for such facile redox reaction. The structural stability might be attributed to the synergism between iron and vanadate as the multivalent Fe adjusted the shift in vanadium coordination when the oxidation state of Vn+ (n = 3–5) changed. Moreover, the two-electrode system of FeV || FeV in a single electrolyzer demonstrated superior cell voltage100 of 1.86 V in comparison to commercial Pt/C || IrO2 electrodes (1.91 V). This work offers facile perspective to produce TMVs as the efficient electrocatalysts for green synthesis of fuel gases.

Bifunctional heterostructured nitrogen-doped carbon-layer-loaded NiSe2-FeSe2 electrocatalyst for efficient water splitting

Developing high-performance, eco-friendly bifunctional electrocatalysts is crucial to popularizing water electrolysis for hydrogen production, but it still presents major challenges. Here, we develop a composite material with NiSe2-FeSe2 heterostructure loaded on N-doped carbon layers by utilizing the metal-organic framework as a sacrificial template (NiSe2-FeSe2/NC). According to microstructural studies, direct contact between NiSe2 and FeSe2 induces charge transfer and enhances conductivity, while sensible arraying of NiSe2-FeSe2/NC nanosheets fully exposes active sites and protects catalysts from violent reaction processes. The NiSe2-FeSe2/NC heterostructured catalysts show excellent bifunctional catalytic activity for hydrogen and oxygen evolution reactions, with overpotentials of 54 and 232 mV at 10 mA cm−2, respectively. Moreover, NiSe2-FeSe2/NC also retains superiority in a two-electrode system, needing lower voltage to drive the overall water splitting at 10 mA cm−2 (1.53 V) than Pt/C||RuO2 as well as long-term stability. This work introduces a novel concept for developing state-of-the-art non-noble metal catalysts for hydrogen production and new insights into interface engineering.

First principles study of V2CT2-based MXenes materials in oxygen reduction and oxygen evolution reactions

The development of bifunctional ORR/OER electrocatalysts with low cost, high activity and sustainable cycle plays an important role in improving the performance of new green energy storage and conversion devices to alleviate the energy crisis and environmental pollution. As a graphene-like two-dimensional inorganic layered compound with unique electrochemistry, MXenes materials have attracted more and more attention in the field of electrocatalytic applications. In this paper, based on the first-principles calculation method based on density functional theory (DFT) and quantum mechanics, an effective scheme for designing efficient ORR/OER bifunctional electrocatalysts by introducing Pd/Pt single atoms to regulate the electronic structure of V2CT2 (T = O, F) is proposed. Firstly, we discussed the stability of the designed series of single-atom catalysts by calculating the formation energy, binding energy and molecular dynamics simulation. Secondly, by comparing the theoretical overpotentials of these single-atom catalysts for ORR and OER, we found that among the designed SACs, V2CO2-Pd, V2CF2-Pd and V2CO2-VO-Pt are catalysts with good bifunctional catalytic activity for ORR/OER. Our work provides some guidance for the application of MXenes materials in the field of electrocatalysis.

Enhanced electrochemical performance of ZrTe-Mn2O3 nanocomposite electrocatalyst for HER and OER in alkaline medium

Electrochemical energy conversion in renewable-energy technologies relies on the OER and HER towards next-generation fuels. Herein, we have coupled zirconia telluride (ZrTe) and manganese oxide (Mn2O3) nanosheets heterointerfaces by a facile hydrothermal method, which are engineered on stainless steel substrate (ZrTe-Mn2O3/SS). The physical properties, including crystallinity, phase purity, morphology, conductivity, and chemical interacted states of the developed composite, are systematically investigated by XRD, HRTEM, I-V, and XPS. The XPS observation showed unique redox properties of hydrogen peroxide species on the ZrTe-Mn2O3 catalyst and the oxidation state of Zr and Mn that was more easily changed in the ZrTe-Mn2O3 electrocatalyst compared with the pristine catalysts. The very decent electrochemical performance of the catalyst activation step (Mn3+→Mn4+ and Zr2+→Zr4+ oxidations) observed from electrochemical cyclic voltammetry (CV) and linear sweep voltammetry (LSV) studies that are tested in the alkaline environment. Concerning higher bifunctional activity for ZrTe-Mn2O3, the current density of 10 mA cm−2 is revealed only at a lower overpotential of 244 mV and Tafel slope of 48 mV/dec toward better OER. At the same time, composite material also exhibited a minimal overpotential of 61 mV toward HER to attain 100 mA/cm2. It was also found that introducing a connection of ZrTe with Mn2O3 improves the precise surface area and exposes more multi-active sites for easy transfer of electrons. In addition, it maintains excellent long-term stability for almost 110 hrs through chronoamperometry, which leads to no activity loss and further represents higher OER/HER activity in industrial applications. We conclusively demonstrate that the first-time reported research provides valuable insights attributed to the defective structure, porous nature, and covalently bridging between atomic-level heterogeneous interfaces, favouring rapid electron transfer process activation for continuously produced O2 and H2 gas bubbles.

Unveiling the potential of ultra-low load Co on porous carbon-rich SiCN(O) fibre mats towards oxygen electrocatalysis in alkaline medium

The development of efficient and cost-effective catalysts for the oxygen electrocatalysis is crucial for advancing renewable energy technologies, such as fuel cells, electrolyzers and metal-air batteries. Herein, we report the high efficiency of Co nanoclusters generated on porous silicon oxycarbonitride (SiCN(O)) fibre mats towards Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER) in alkaline medium. Porous SiCN(O) ceramic fibrous supports were synthesized via electrospinning of a blend of oligosilazane Durazane 1800, polyacrylonitrile and polystyrene followed by an appropriate heat-treatment. Co nanoparticles with a remarkably low mass loading (4 wt%) were immobilized on the SiCN(O) fibres for efficient bifunctional catalytic activity towards OER/ORR. The catalysts exhibited ORR activity (onset potential (E0) of 0.83 V vs. RHE) and excellent stability (80 h) in alkaline medium. Concomitantly, the catalyst required only 1.67 V to drive a current density of 10 mA cm−2 in 1 M KOH for OER.

The application of Co3S4@NCNT/NCHS with excellent bifunctional catalytic activity in aqueous and flexible Zn-air batteries

In this work, we prepared a hybrid structure Co3S4@NCNT/NCHS using SiO2 nanospheres as a template. The structure is supported by hollow carbon spheres (NCHS), which are coated by Co3S4 nanoparticles and cross-linked N-doped carbon nanotubes. The combination of Co3S4 with N-doped carbon material significantly improves the electrocatalytic activity. In addition, the presence of N-doped carbon nanotubes induces more defects, which can regulate the electronic configuration of the material and improve its electrical conductivity. Therefore, Co3S4@NCNT/NCHS has good catalytic performance. At 10 mA cm−2, the OER overpotential of Co3S4@NCNT/NCHS is only 230 mV, which is lower than that of the commercial catalyst RuO2, and the ORR half-wave potential can reach 0.80 V. In the battery discharge test, Co3S4@NCNT/NCHS based ZABs can discharge continuously for 71.5 h, the specific capacity of 790.12 mA h g−1, power density of 113.09 m W cm−2, better than Pt/C+RuO2 battery. When the current density is 3 mA cm−2, ZABs assembled with Co3S4@NCNT/NCHS as catalyst can maintain a voltage gap of 0.62 V to 0.63 V within 300 h without significant change. When the current density is increased to 5 mA cm−2, ZABs based on Co3S4@NCNT/NCHS can be stably cycled for 300 h at a voltage gap between 0.80 V and 0.82 V.

Manipulating the Electronic Properties of an Fe Single Atom Catalyst via Secondary Coordination Sphere Engineering to Provide Enhanced Oxygen Electrocatalytic Activity in Zinc-Air Batteries.

Oxygen reduction and evolution reactions are two key processes in electrochemical energy conversion technologies. Synthesis of nonprecious metal, carbon-based electrocatalysts with high oxygen bifunctional activity and stability is a crucial, yet challenging step to achieving electrochemical energy conversion. Here, an approach to address this issue: synthesis of an atomically dispersed Fe electrocatalyst (Fe1/NCP) over a porous, defect-containing nitrogen-doped carbon support, is described. Through incorporation of a phosphorus atom into the second coordination sphere of iron, the activity and durability boundaries of this catalyst are pushed to an unprecedented level in alkaline environments, such as those found in a zinc-air battery. The rationale is to delicately incorporate P heteroatoms and defects close to the central metal sites (FeN4P1-OH) in order to break the local symmetry of the electronic distribution. This enables suitable binding strength with oxygenated intermediates. In situ characterizations and theoretical studies demonstrate that these synergetic interactions are responsible for high bifunctional activity and stability. These intrinsic advantages of Fe1/NCP enable a potential gap of a mere 0.65V and a high power density of 263.8mWcm-2 when incorporated into a zinc-air battery. These findings underscore the importance of design principles to access high-performance electrocatalysts for green energy technologies.

Dual‐Carbon Assisted Oxygen Vacancy Engineering for Optimizing Mn(III) Sites to Enhance Zn–air Battery Performances

AbstractOwing to kinetic‐sluggish nature of electrocatalytic oxygen transformation processes, it is pivotal to develop durable and efficient bifunctional air electrode catalysts for fabricating high‐performance Zn–air batteries (ZABs). In this work, oxygen vacancy (Ov) induced Mn(III) sites optimization is achieved via nano‐micro structure modulation. Protonated carbon nitride (p‐C3N4) is applied as a structure‐stiffening module to immobilize α‐MnO2 on N/P‐doped active carbon (NPAC) and induce Ov construction. X‐ray adsorption spectra (XAS) disclose the formation of Ov and Mn(III) sites in MCC, the unit coordination structure is well maintained with the aid of a dual‐carbon strategy. Mn(III) sites efficiently catalyze oxygen reduction/evolution reaction (ORR/OER), MCC shows high half‐wave potential (E1/2) of 0.88 V for ORR and low potential at 10 mA cm−2 (Ej = 10) of 1.64 V for OER. According to density functional theory (DFT) simulations analysis, the gorgeous bifunctional activity is owing to that optimized charge distribution facilitates the intermediates transformation. Aqueous ZABs based on MCC manifests high peak power density of 452 mW cm−2 and durable cycling stability of 1640 h. Quasi‐solid‐state ZABs based on MCC also show satisfactory performances (175 mW cm−2, 105 h). This work provides the route to develop efficient and durable electrocatalyst for constructing ZABs with long lifespan and high‐power‐density.

Surface-Engineered Ni2P: An Efficient Oxygen Electrocatalyst for Zinc-Air Battery.

The surface engineering of electrocatalysts is one of the promising strategies to increase the intrinsic activity of electrocatalysts. It generates anion/cation vacancy defects and increases the electrochemically active surface area. We describethe surface engineering of Ni2P to favorably tune the bifunctional oxygen electrocatalytic activity and the development of a rechargeable zinc-air battery (ZAB). Ni2P encapsulated with N and P-dual doped carbon (Ni2P@NPC) is synthesized using a single-source precursor complex tris-(2,2'-bipyridine)nickel(II) bis(hexafluorophosphate). The surface engineering of the as-synthesized Ni2P@NPC is achieved by the controlled acid treatment at room temperature. The surface engineering removes carbon debris and opens the pores, exfoliates the encapsulating carbon layer, increases the P-vacancy in the crystal lattice, and boosts the electrochemically active surface area. Thesurface-engineered catalyst exhibits enhanced bifunctional activity towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrocatalytically active sites of engineered catalysts are highly accessible for facilitated electron transfer kinetics. P-vacancy favors the facile formation of defect-rich OER active metal oxyhydroxide species. The rechargeable ZAB based on the engineered catalyst delivers a specific capacity of 770.25 mA h gZn-1, energy density of 692 Wh kgZn-1, and excellent charge-discharge cycling performance with negligible voltaic efficiency loss (0.6 %) after 100 h.

The Asymmetrical Fe-O-Se Bonds in Fe2O(SeO3)2 Boosting Bifunctional Oxygen Electrocatalytic Performance for Zinc-Air Battery.

HereFe2O(SeO3)2/Fe3C@NC catalysts with high performance werefabricated for zinc-air batteries (ZABs). The experimental results confirmed that the existence of Fe-O-Se bonds in Fe2O(SeO3)2 crystal phase, and the Fe-O-Se bonds could obviously enhance ORR and OER catalytic performance of Fe2O(SeO3)2/Fe3C@NC. Density functional theoretical calculations (DFT) confirmed that the Fe2O(SeO3)2 in Fe2O(SeO3)2/Fe3C@NC had a higher d-band center of Fe atom and a lower p-orbital coupling degree with its own lattice O atom than Fe2O3, which leads to Fe site of Fe2O(SeO3)2 being more likely to adsorb external oxygen intermediates. The Fe-O-Se bonds in Fe2O(SeO3)2 results in the modification of coordination environment of Fe atoms and optimizes the adsorption energy of Fe site for oxygen intermediates. Compared with Fe2O3/Fe3C@NC, the Fe2O(SeO3)2/Fe3C@NC showed obvious enhancements of ORR/OER catalytic activities with a half-wave potential of 0.91 V for ORR in 0.1 M KOH electrolyte and a low overpotential of 345 mV for OER at 10 mA cm-2 in a 1.0 M KOH electrolyte. The peak power density and specific capacity of Fe2O(SeO3)2/Fe3C@NC-based ZABs are higher than those of Pt/C+RuO2-ZABs. The above results demonstrate that the asymmetrical Fe-O-Se bonds in Fe2O(SeO3)2 plays a key role in improving the bifunctional catalytic activities of ORR/OER for ZABs.

The “d-p orbital hybridization”-guided design of novel two-dimensional MOFs with high anchoring and catalytic capacities in Lithium − Sulfur batteries

The energy system of lithium-sulfur batteries is quite promising, however, lithium-sulfur batteries still suffer from considerable problems, such as the abominable shuttle effect of polysulfides (LiPSs), the low conductivity of the solid-phase products, the slow redox kinetics during charging and discharging, and the volume expansion. Herein, the hybridization pattern between the d-orbitals of various transition metal atoms and the p-orbitals of sulfides is revealed grounded in the theory of density function, which explains the high adsorption strength of two-dimensional metal–organic frameworks (MOFs) with LiPSs and accelerates the screening of high-performance anchoring and catalytic materials. The results elucidate that the coordinated transition metal–organic frameworks (Mo-NH MOF) monolayers increase the capacity of LiPSs to anchor by forming more π-bonds from the hybridization of the S p orbitals and Mo d orbitals. Notably, Mo-NH MOF exhibits bifunctional catalytic activity for sulfur reduction as well as Li2S decomposition reactions during charging and discharging, which improves the conversion efficiency of redox reactions. As a result, new MOF materials featuring unique active centers and the potential mechanism by which the active centers modulate the performance of the substrate materials are revealed, and this finding may accelerate the development of high-performance Li-S batteries.

Heterointerface engineering of yolk-shell-structured Mn2O3/RuO2 for boosting oxygen electrocatalysis in rechargeable liquid and flexible zinc-air batteries

Rational construction of high-efficient bifunctional oxygen electrocatalysts is of crucial significance for rechargeable Zn-air batteries (ZABs). Here, the yolk-shell-structured Mn2O3/RuO2 heterojunction is purposely constructed via the Kirkendall effect as a robust bifunctional oxygen electrocatalyst for simultaneously driving oxygen evolution and reduction reactions (OER and ORR). The strong interactions between Mn2O3 and RuO2 induces the surface reconstruction that brings the electronic transfer from Mn to Ru, and the changes of coordination environments of metal atoms. Meanwhile, the yolk-shell structure enables maximum contact of the active sites with the electrolyte and prevents the dissolution and peroxidation of active species. As a result, the yolk-shell-structured Mn2O3/RuO2 shows an outstanding bifunctional activity with a very low potential gap of ΔE = 0.60 V. Moreover, the ZABs assembled with Mn2O3/RuO2 render a large open circuit voltage of 1.53 V, a high specific capacity of 742.1 mA h g−1 and an exceptional cycling stability over 850 h that significantly outperforms those of Pt/C+RuO2-based ZABs. Moreover, the self-made flexible solid-state ZAB with Mn2O3/RuO2 cathode also shows good charge–discharge reversibility and flexibility at different bending angles. This work provides a feasible method for the design of efficient oxygen electrocatalysts to promote the practical application of ZABs.

Structurally optimized rosette-like microspheres carbon with Fe-Ni single atom sites for bifunctional oxygen electrocatalysis in Zinc-Air batteries

Developing a secure and effective bifunctional oxygen catalyst for the ORR and OER is still a significant obstacle in the design of rechargeable zinc-air batteries. Here, a hollow rose-shaped bifunctional electrocatalyst is synthesized with an sacrificial template strategy (FeNi-NC). X-ray absorption fine structure analysis reveals the FeNi-NC catalyst contains FeN4 and NiN4 active sites as well as FeNi3 alloy. This hollow, flower-like structure performs low density, large specific surface area, and high permeability. Its inner cavities not only provide additional triple-phase interfaces to accelerate the reduction and oxidation of O2, but also enhance the diffusion of reactants on the catalyst. By controlling the input of Fe and nickel metal salts, the dispersion of active sites can be effectively tuned. Owing to the large number of exposed active sites on the carbon nanosheets, the synthesized FeNi-NC catalysts exhibit high electrocatalytic activity in both ORR (E1/2 = 0.852 V) and OER (ηj=10 = 359 mV). The construction of rechargeable zinc-air batteries resulted in a high power density of 135.78 mW cm−2, a better specific capacitance of 726.9 Wh kgZn−1 and 210 h enduring durability. More importantly, density functional theory (DFT) calculations indicate that the electronic interactions between Fe/Ni and nitrogen-doped carbon matrices play a pivotal role in enhancing the electrocatalytic performance of functional groups. These interactions effectively disrupt the electronic neutrality of carbon atoms, thereby accelerating the kinetics of the reaction. This research provides a new method for the preparation of single atom catalysts with bifunctional activities.

Oriented construction of lignin-derived carbon hybrid electrocatalyst with superwettable surface and Co-based heterostructure for overall water splitting

Converting lignin waste into carbon hybrid catalysts for water electrolysis engenders a beneficial scenario for both the valorization of waste carbon resources and the reduction of hydrogen production costs, which remains a grand challenge. Hence, we report a novel lignin-derived carbon hybrid electrocatalyst as a low-cost and highly efficient bifunctional electrocatalyst for overall water splitting, prepared by a feasible strategy involving NaCl-assisted pyrolysis and subsequent oxidation-phosphorization. Notably, this strategy can not only regulate the composition of CoP/CoOx nano-heterostructures but also improve the structural properties of porous carbon matrix. Profiting from superwettable surface, ultrafine Co-based heterojunctions and large active area, the optimal CoP/CoOx-HPC catalyst exhibits exceptional bifunctional catalytic activity in 1 M KOH electrolyte, requiring only small overpotentials of 396 and 522 mV for HER and OER, respectively, to achieve a large current density of 400 mA cm−2. Meanwhile, the assembled alkali-electrolyzer using CoP/CoOx-HPC as both cathode and anode needs a relatively low voltage of 2.31 V at 400 mA cm−2, significantly outperforming the commercial couple of Pt/C || RuO2. This work can be of value in the design of the low-cost and highly active lignin-derived electrocatalysts and also serve as guidance for the high-value utilization of lignin or even other biomass wastes.

Simple generic self-assembly fabrication of transition metal borates on polyaminophenylboric acid modified foam nickel for highly-efficient overall water splitting

Water electrocatalysis for hydrogen production as a prospect strategy to store renewable energy and reduce carbon emissions has attracted great attention, and exploring water electrolysis catalysts has become a research hotspot for widespread industrial water electrolysis application. Very recently, transition metal borates have been demonstrated great potential for electrocatalytic hydrogen or oxygen evolution in alkaline media. However, a generic method for fabricating transition metal borates as bifunctional oxygen catalysts are still challenging. Herein, through a two-step process including poly-aminophenylboronic acid electrodeposition and subsequent electrostatic self-assembly of transitional metal ions, for the first time, to our best knowledge, a simple and generic approach to fabricate polyaminophenylborate transition metal salt modified nickel foam electrodes (PAB-M/NF, M represents transition metal element) was developed for highly efficient water splitting. As a proof of concept, the obtained PAB-Ru/NF exhibited remarkable bifunctional HER and OER catalytic activities and stability in alkaline medium. To drive the HER and OER with a current density of 10 mA cm−2 in 1 M KOH electrolyte, PAB-Ru/NF only required an overpotential of 14 mV and 301 mV, respectively. Moreover, even at a great current density of 250 mA cm−2, PAB-Ru/NF can exhibit very favorable long-term stability for over 35 h. When assembled into an electrolyzer with PAB-Ru/NF as both the anode and cathode, a current density of 10 mA cm−2 can be achieved at a very low cell voltage of 1.50 V. In addition, the other PAB-M/NF catalysts (M including but not limited to Fe, Co and Ni) prepared by the same way also show excellent bifunctional HER and OER catalytic activities and durability. This study provides a prospective and economically feasible generic approach for developing practical bifunctional catalysts for industrial water electrolysis.

Eco-Friendly Mechanochemical Synthesis of Bifunctional Metal Oxide Electrocatalysts for Zn-Air Batteries.

The development of green and environmentally friendly synthesis methods of electrocatalysts is a crucial aspect in decarbonizing energy generation. In this study, eco-friendly mechanochemical synthesis of perovskite metal oxide-carbon black composites is proposed using different conditions and additives such as KOH. Furthermore, the optimization of ball milling conditions, including time and rotational speed, is studied. The mechanochemical synthesis in solid-state conditions without additives produces electrocatalysts that exhibit the highest bifunctional electrochemical activity towards both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Moreover, this synthesis demonstrates a lower Environmental Impact Factor (E-factor), indicating its greener nature, and due to its simplicity, it has a great potential for scalability. The obtained bifunctional electrocatalysts have been tested in a rechargeable zinc-air battery (ZAB) for 22 h with similar performance compared to the commercial catalyst (Pt/C) at significantly lower cost. These promising findings are attributed to the enhanced interaction between the perovskite metal oxide and carbon material and the improved dispersion of the perovskite metal oxide on the carbon materials.

Surface reconstruction of hierarchical CoNiP@Ni2P nanoarray to promote overall water splitting

Efficient water splitting remains a challenge to produce clean and pure H2 in an industrial scale for the lack of high-performance cost-effective stable electrocatalysts of hydrogen and oxygen evolution (HER and OER). Surface engineering is a novel proposal to upgrade the electrocatalytic performances of HER and OER catalysts. Herein, a hierarchical architecture composed of carbon-supported CoNiP nanoplates (NPs) on Ni2P nanowire was constructed. The nanoarray of CoNiP@Ni2P heterostructure shows a high bifunctional activity of HER and OER. The overpotential is 46 mV required for HER at 10 mA·cm−2 and 292 mV for OER at 100 mA·cm−2 in 1 mol·L−1 KOH. In addition, the nanoarray of CoNiP@Ni2P heterostructure also shows a high stability for HER. The HER activity can be maintained at 11 mA·cm−2 without loss after 50 h cathode polarization at the overpotential of 100 mV, while the OER activity continuously increases from 26 to 64 mA·cm−2 at an overpotential of 400 mV after 50 h anode polarization. The enhancement of the oxygen evolution performance can be ascribed to the surface reconstruction of CoNiP/Ni2P heterostructure nanoarray, which can offer more active sites to OER. Density functional theory (DFT) reveals surface reconstruction can create an oxygen-rich surface in favor of intermediate adsorption, thus enabling a fast OER kinetics at the interface of NiCoOOH/Ni2P heterostructure. This work highlights surface reconstruction adaptability to design advanced catalysts of efficient water splitting for commercial H2 production.

Assembly of low-voltage driven co-production of hydrogen and sulfur via Ru nanoclusters on metal-sulfur coordination: Insights from DFT calculations

Herein, we propose a simple and rapid approach for synthesizing a CuS/Ru composite that serves as a bifunctional electrocatalyst to promote hydrogen production and concurrently convert sulfion into a value-added sulfur product. This composite comprises Ru nanoclusters supported on the CuS nanostructure, achieved through simple pulsed laser irradiation in liquid approach. The optimized CuS/Ru-30 electrocatalyst demonstrates remarkable bifunctional electrocatalytic activity, exhibiting a negligible working potential of 0.28 V (vs. RHE) for the anodic sulfion oxidation reaction (SOR) and a minimal overpotential of 182 mV for cathodic hydrogen evolution reaction (HER) to achieve 10 mA cm−2 of current density. Moreover, the CuS/Ru-30 electrocatalyst shows exceptional selectivity for converting sulfion into valuable sulfur during anodic oxidation reactions. Remarkably, in a two-electrode electrolyzer system utilizing CuS/Ru-30 as both the anode and cathode, the SOR + HER coupled water electrolysis system demands only 0.52 V to reach 10 mA cm−2, which is considerably lesser compared to the OER + HER coupled water electrolysis (1.85 V). The experimental results and density function theory (DFT) calculations reveal that the strong electron interaction between CuS and Ru nanoclusters generates a built-in electric field, greatly enhancing electron transfer efficiency. This significantly boosts the HER performance and facilitates the adsorption and production of sulfur intermediates. This study presents a rapid and simple strategy for synthesizing a dual-functional catalyst suitable for low-voltage hydrogen generation while facilitating the recovery of valuable sulfur sources.

Microenvironment Tailoring of NiCo Alloys Coupled with FePc as Efficient Bifunctional Catalysts for High-Rate Zn-Air Batteries.

The practical application of Zn-air batteries require exploring cost-effective and durable bifunctional electrocatalysts. However, the simultaneous preparation of catalysts with bifunctional activities for oxygen reduction reaction (ORR) and oxygen precipitation reaction (OER) remains challenging. Herein, we synthesized a novel hybrid catalyst (FePc/NiCo/CNT), which couples NiCo alloy with FePc through electrostatic interaction. The interaction between FePc and NiCo alloy can enhance the intrinsic catalytic activity of the active site Fe-N4 and prevent the electrolyte corrosion of the metal alloy, ultimately improving the stability of the catalyst by the microenvironment-tailoring strategy. The resultant FePc/NiCo/CNT catalyst exhibits outstanding oxygen reduction reaction (ORR) activity with a half-wave potential of 0.88 V, which is attributed to the abundant Fe-Nx active sites. Furthermore, the electron interactions between NiCo/CNT and FePc accelerate electron transfer and enhance the activation of oxygen intermediates, consequently boosting the OER activity with an overpotential of 260 mV at 10 mA cm-2. The Zn-air batteries assembled with FePc/NiCo/CNT show a high power density of 175.1 mW cm-2 and excellent cycling stability for up to 430 h at 20 mA cm-2. The preparation of oxygen electrode catalysts for renewable clean energy devices can be made more convenient with this directly engineered strategy for ORR and OER active centers.

Promoting Electrocatalytic Oxygen Reactions Using Advanced Heterostructures for Rechargeable Zinc-Air Battery Applications.

In order to facilitate electrochemical oxygen reactions in electrically rechargeable zinc-air batteries (ZABs), there is a need to develop innovative approaches for efficient oxygen electrocatalysts. Due to their reliability, high energy density, material abundance, and ecofriendliness, rechargeable ZABs hold promise as next-generation energy storage and conversion devices. However, the large-scale application of ZABs is currently hindered by the slow kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). However, the development of heterostructure-based electrocatalysts has the potential to surpass the limitations imposed by the intrinsic properties of a single material. This Account begins with an explanation of the configurations of ZABs and the fundamentals of the oxygen electrochemistry of the air electrode. Then, we summarize recent progress with respect to the variety of heterostructures that exploit bifunctional electrocatalytic reactions and overview their impact on ZAB performance. The range of heterointerfacial engineering strategies for improving the ORR/OER and ZAB performance includes tailoring the surface chemistry, dimensionality of catalysts, interfacial charge transfer, mass and charge transport, and morphology. We highlight the multicomponent design approaches that take these features into account to create advanced highly active bifunctional catalysts. Finally, we discuss the challenges and future perspectives on this important topic that aim to enhance the bifunctional activity and performance of zinc-air batteries.