High-performance Bifunctional Catalysts Research Articles

Constructing a Self-Supported Bifunctional Multiphase Heterostructure for Electrocatalytic Overall Water Splitting.

Developing well-performing and stable bifunctional electrocatalysts is of great importance for efficient green hydrogen production through water electrolysis. Herein, a three-dimensional self-supported CoMoS3.13/FeS2/Co3S4 on carbon paper (FeCoMoS/CP) heterostructure with interconnected nanosheets for overall water splitting was fabricated by a facile hydrothermal method followed by vulcanization treatment. The FeCoMoS/CP heterostructure with high structural integrity and more accessible active sites can effectively optimize the electronic structure through component regulation to achieve enhanced catalytic activity. Significantly, the FeCoMoS/CP required overpotentials of 257 mV at 50 mA cm-2 for OER and 280 mV at 20 mA cm-2 for HER. Importantly, the assembled FeCoMoS/CP||FeCoMoS/CP alkaline electrolyzer achieved a superior cell voltage of 1.48 V at 10 mA cm-2 with superb long-term stability, which implies a remarkable electrocatalytic performance of the FeCoMoS/CP heterostructure for overall water splitting. This work provides an applicable route for synthesizing high-performance bifunctional catalysts toward water electrolysis.

Complementary Multisite Turnover Catalysis toward Superefficient Bifunctional Seawater Splitting at Ampere-Level Current Density.

The utilization of seawater for hydrogen production via water splitting is increasingly recognized as a promising avenue for the future. The key dilemma for seawater electrolysis is the incompatibility of superior hydrogen- and oxygen-evolving activities at ampere-scale current densities for both cathodic and anodic catalysts, thus leading to large electric power consumption of overall seawater splitting. Here, in situ construction of Fe4N/Co3N/MoO2 heterostructure arrays anchoring on metallic nickel nitride surface with multilevel collaborative catalytic interfaces and abundant multifunctional metal sites is reported, which serves as a robust bifunctional catalyst for alkaline freshwater/seawater splitting at ampere-level current density. Operando Raman and X-ray photoelectron spectroscopic studies combined with density functional theory calculations corroborate that Mo and Co/Fe sites situated on the Fe4N/Co3N/MoO2 multilevel interfaces optimize the reaction pathway and coordination environment to enhance water adsorption/dissociation, hydrogen adsorption, and oxygen-containing intermediate adsorption, thus cooperatively expediting hydrogen/oxygen evolution reactions in base. Inspiringly, this electrocatalyst can substantially ameliorate overall freshwater/seawater splitting at 1000mA cm-2 with low cell voltages of 1.65/1.69V, along with superb long-term stability at 500-1500mA cm-2 for over 200 h, outperforming nearly all the ever-reported non-noble electrocatalysts for freshwater/seawater electrolysis. This work offers a viable approach to design high-performance bifunctional catalysts for seawater splitting.

Synergistic Mo and W single atoms co-doped surface hydroxylated NiFe oxide as bifunctional electrocatalysts for overall water splitting

Two novel defect engineering strategies, surface hydroxylation and single atom (SA) doping, are explored to fabricate a high performance bifunctional water electrolysis catalyst, synergistic Mo and W SAs co-doped surface hydroxylated NiFe oxide (FN-MoWact). The product catalyst achieves ultralow overpotentials of 196 and 246 mV for oxygen evolution reaction (OER) and decent overpotentials of 79 and 246 mV for hydrogen evolution reaction (HER) at current densities of 10 and 500 mA cm−2, respectively. For overall water splitting, the FN-MoWact//FN-MoWact couple requires ultralow cell voltages of 1.504 and 1.729 V to deliver current densities of 10 and 500 mA cm−2, respectively, and remains stable after a 100-hour operation at an initial current density of 534 mA cm−2. The enhanced electrocatalytic activities are attributed to surface hydroxylation and doping of synergistic Mo and W SAs. The two defect engineering modifications, as supported by analyses of density functional theory calculations and in-situ X-ray absorption spectroscopy, lead to a proper reduction in metal-oxygen covalency, thus minimizing the energy difference of the rate-determining step of the OER process, and create surface active sites with a d-band center located closer to the Fermi level, thus properly strengthening proton binding to enhance HER activities.

Recycling the spent cobalt-based perovskites for the high-active oxygen catalysts in zinc-air batteries

Cobalt (Co) is widely used in energy storage and conversion devices, although its content on our planet is not adequate. Therefore, recycling Co from the spent Co-enriched materials is indispensable. Co-based perovskites, which contain abundant Co, are extensively utilized in solid oxide fuel cells, three-way catalysts, and oxygen-permeable membranes, and the recovery of Co from the spent Co-based perovskites is necessary to meet the long-term requirement of Co. In this work, a facile and universal thermal reduction method (750 °C and N2 atmosphere) is employed to convert the spent cobalt-based perovskites into high-performance bifunctional oxygen catalysts for zinc-air batteries (ZABs), achieving high-efficient Co recovery and re-utilization. At high temperatures, melamine and dopamine hydrochloride are transformed into carbon nanotubes, C3N4 and reducing gases (such as NH3 and H2). Simultaneously, the metal elements in the spent Co-based perovskites (SrNb0.1Co0.7Fe0.2O3,SNCF) are converted into nano-scale alloy particles and metal nitrides. Then, the phase structures, micromorphology, and element valences of the obtained multiphase oxygen catalyst (SNCF–Ni-PM) are characterized by X-ray diffraction, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemical properties, including oxygen catalytic activities and stability, of SNCF-Ni-PM are measured by linear sweep voltammetry, chronopotentiometry, chronoamperometry, and cyclic voltammetry methods. Considering the practical applications, the aqueous and solid-state ZABs are assembled and measured. The results demonstrate that the multiphase SNCF-Ni-PM mainly includes carbon nanotubes, C3N4 nanosheets, and FeNiN or CoFe nanoparticles. Moreover, SNCF-Ni-PM exhibits excellent bifunctional oxygen catalytic activity, with an oxygen evolution reaction (OER) potential at 10 mA cm−2 of 1.51 V and an oxygen reduction reaction (ORR) half-wave potential of 0.77 V, outperforming most of the reported oxygen catalysts. Using SNCF-Ni-PM, the aqueous and solid-state ZABs can achieve high power densities of 295.9 and 228.4 mW cm−2, respectively, being superior to most ZABs. In addition, the aqueous ZAB with SNCF-Ni-PM can operate stably for 300 h with a slight degradation. This work provides a feasible method for effectively recycling Co from the spent Co-based perovskites.

Oxygen Vacancy-Enhanced Ni3N-CeO2/NF Nanoparticle Catalysts for Efficient and Stable Electrolytic Water Splitting.

Highly efficient and cost-effective electrocatalysts are of critical significance in the domain of water electrolysis. In this study, a Ni3N-CeO2/NF heterostructure is synthesized through a facile hydrothermal technique followed by a subsequent nitridation process. This catalyst is endowed with an abundance of oxygen vacancies, thereby conferring a richer array of active sites. Therefore, the catalyst demonstrates a markedly low overpotential of 350 mV for the Oxygen Evolution Reaction (OER) at 50 mA cm-2 and a low overpotential of 42 mV for the Hydrogen Evolution Reaction (HER) at 10 mA cm-2. Serving as a dual-function electrode, this electrocatalyst is employed in overall water splitting in alkaline environments, demonstrating impressive efficiency at a cell voltage of 1.52 V of 10 mA cm-2. The in situ Raman spectroscopic analysis demonstrates that cerium dioxide (CeO2) facilitates the rapid reconfiguration of oxygen vacancy-enriched nickel oxyhydroxide (NiOOH), thereby enhancing the OER performance. This investigation elucidates the catalytic role of CeO2 in augmenting the OER efficiency of nickel nitride (Ni3N) for water electrolysis, offering valuable insights for the design of high-performance bifunctional catalysts tailored for water splitting applications.

Iron, Tungsten Dual-Doped Nickel Sulfide as Efficient Bifunctional Catalyst for Overall Water Splitting.

Developing low-cost and highly efficient bifunctional catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is a challenging problem in electrochemical overall water splitting. Here, iron, tungsten dual-doped nickel sulfide catalyst (Fe/W-Ni3S2) is synthesized on the nickel foam, and it exhibits excellent OER and HER performance. As a result, the water electrolyze based on Fe/W-Ni3S2 bifunctional catalyst illustrates 10mAcm-2 at 1.69V (without iR-compensation) and highly durable overall water splitting over 100h tested under 500mAcm-2. Experimental results and DFT calculations indicate that the synergistic interaction between Fe doping and Ni vacancy induced by W leaching during the in situ oxidation process can maximize exposed OER active sites on the reconstructed NiOOH species for accelerating OER kinetics, while the Fe/W dual-doping optimizes the electronic structure of Fe/W-Ni3S2 and the binding strength of intermediates for boosting HER. This study unlocks the different promoting mechanisms of incorporating Fe and W for boosting the OER and HER activity of Ni3S2 for water splitting, which provides significant guidance for designing high-performance bifunctional catalysts for overall water splitting.

Heterostructure catalyst coupled wood-derived carbon and cobalt-iron alloy/oxide for reversible oxygen conversion

As promising energy-storage devices, zinc–air batteries (ZABs) exhibit slow reaction kinetics for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occurring at their electrodes. High-performance bifunctional catalysts must thus be synthesized to accelerate the reversible conversion of oxygen and improve the rate and overall performance of ZABs. Herein, we reported the promising prospects of self-supported composite electrodes composed of wood-derived carbon (WDC) and bimetallic cobalt-iron alloys/oxides (CoFe-CoFe2O4@WDC) as efficient electrocatalysts for alkaline ORR/OER. WDC provided a favorable three-phase interface for heterogeneous reactions owing to its layered porous structure and genetic stability, thereby enabling mass diffusion and improving reaction kinetics. The CoFe2O4 spinel surface was reduced to bimetallic CoFe alloy to form abundant heterostructure interfaces that promote electron transfer. Under alkaline conditions, the optimized composite electrode exhibited a remarkable high half-wave potential of 0.85 V and an exceptionally low overpotential of 1.49 V. It also exhibited stable performance over an impressive 2340 cycles in a ZAB. Theoretical calculations also confirmed that the heterointerface addresses the issue of proton scarcity throughout the reaction and actively facilitates the creation of O–O bonds during the reversible transformation of oxygen. This study introduces a new concept for developing bifunctional and efficient electrocatalysts based on charcoal and encourages the sustainable and high-value use of forest biomass resources.Graphical

Superhydrophobic Co/Fe sulfide nanoparticles and single-atoms doped carbon nanosheets composite air cathode for high-performance zinc-air batteries

Development of a high-performance bifunctional catalyst is essential for the actual implementation of zinc-air batteries in practical applications. Herein, a bifunctional cathode of Co3S4/FeS heterogeneous nanoparticles embedded in Co/Fe single-atom-loaded nitrogen-doped carbon nanosheets is designed. Cobalt-iron sulfides and single atomic sites with Co-N4/Fe-N4 configurations are confirmed to coexist on the carbon matrix by EXAFS spectroscopy. 3D self-supported super-hydrophobic multiphase composite cathode provides abundant active sites and facilitates gas–liquid-solid three-phase interface reactions, resulting in excellent electrocatalytic activity and batteries performance, i.e., an OER overpotential (η10) of 260 mV, a half-wave potential (E1/2) of 0.872 V for ORR, a ΔE of 0.618 V, and a discharge power density of 170 mW cm−2, a specific capacity of 816.3 mAh g−1. DFT analysis shows multiphase coupling of sulfide heterojunction through single-atomic metal doped carbon nanosheets reduces offset on center of electronic density of states before and after oxygen adsorption, and spin density of adsorbed oxygen with same spin orientation, leading to weakened charge/spin interactions between adsorbed oxygen and substrate, and a lowered oxygen adsorption energy to accelerate OER/ORR.

An ultrathin flocculent Co9S8/Ni3S2 hybrid as high-performance bifunctional catalyst for overall water splitting

Modern industrial hydrogen production is a crucial solution to address the energy crisis. Therefore, the development of a cost-effective and highly efficient hydrolytic hydrogen production catalyst holds significant practical importance. In this study, we propose to synthesize an efficient bifunctional electrocatalyst of Co9S8/Ni3S2 grown on nickel foam (NF) by a one-step hydrothermal method, which has a large specific surface area due to its flocculated structure. Through electrochemical testing, the Co9S8/Ni3S2/NF electrode exhibits remarkable performance in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Specifically, low overpotentials of 53.6, 90.2, and 209.2 mV are required to achieve current densities of 10, 20, and 100 mA/cm2 during HER, respectively. Similarly, for OER, the overpotentials are only 107.6, 150.6, and 350.4 mV. Additionally, the Co9S8/Ni3S2/NF electrode demonstrates a small Tafel slope of 68.7 mV/dec for HER and 91.8 mV/dec for OER, indicating efficient reaction kinetics. Notably, the electrode exhibits exceptional long-term stability. Moreover, in a self-assembled monolithic water splitting device with Co9S8/Ni3S2/NF electrodes as cathode and anode, a cell potential of 1.55 V is required to drive the overall water splitting process at a current density of 10 mA/cm2, and the reaction shows excellent stability with a loss of voltage of only 16.5 mV over a 10-hour period. This paper presents a simple and innovative approach for constructing bimetallic sulfides electrocatalysts.

In-situ construction defect-rich CuNiCoS4 /1T-MoS2 heterostructures as superior electrocatalysts for water splitting

Rational design and construction of bifunctional heterostructure electrocatalysts with high-conductivity and more active sites is imperative for water splitting. Herein, based on the tunable property of layered double hydroxide laminates cations, topological transformation technology and template confine method, a series of high-performance bifunctional catalysts composed of transition metal doping NiCo2S4 (MNiCoS4, M = Cu, Fe, Zn, Mn) and 1T-MoS2 were in-situ fabricated on nickel foam. In particular, CuNiCoS4/1T-MoS2 exhibits an ultralow overpotential of 163 mV at 50 mA cm−2 for oxygen evolution reaction (OER) and favorable hydrogen evolution reaction activity. The two-electrode system requires only 1.52 V to attain a current density of 10 mA cm−2. To the best of our knowledge, its OER electrocatalytic activity far exceed state-of-art catalysts reported. The outstanding performance of this series of catalysts can be attributed to two aspects. First, the highly conductive 1T-MoS2 can facilitate electron transfer, and second, the defect-rich heterostructure can effectively regulate the electronic structure of the active metal and expose abundant active sites. This work provides a valuable strategy for developing high activity electrocatalysts for efficient water splitting.

Surface modulation of transition-metal-doped MoS2@graphite felt for bifunctional catalysis in Zn-air batteries

Surface modulation is essential to bifunctional catalysis especially for energy devices. Herein, transition-metal-doped MoS2 is shown to have modulated interfacial states to facilitate bifunctional catalysis of the oxygen reduction and evolution reactions (ORR/OER) in Zn-air batteries. The uniform distribution, vertically aligned layer, and stable Fe doped MoS2 semiconducting nanoparticles produce promising bifunctional catalysis in the fabricated Zn-air batteries. Electrochemical assessment reveals that the surface electronic states and adsorption/desorption effects are crucial to the properties and stability of the bifunctional electrode in ORR/OER. The new findings divulge an effective strategy to modulate surface/interface states to produce high-performance bifunctional catalysts for the oxygen reduction/evolution reactions.

The performance improvement method of g-C3N4 based catalyst for hydrogen production from ammonia borane: A DFT investigation

In the study, based on the purpose of efficient catalytic AB for hydrogen production, the photochemical properties influence of metal(Ru, Ni) and nonmetal(B,P) elements doping on the g-C3N4 are studied systematacially. The design method of high performance bifunctional catalyst of photocatalysis and metal catalysis are provided. The results have proved that both non-metals B, P and metal Ru, Ni have an efficient regulatory effect on the band structure of g-C3N4, which make the band gap of the clean monolayer g-C3N4(001) decrease from 1.175 eV to 0.261eV(B-g-C3N4(001)) and 0.671eV(P-g-C3N4(001)), 0.164 eV(Ni-g-C3N4(001)) and 0.260 eV(Ru-g-C3N4(001)), respectively. B element have the better modification effect compared with the P element. The reduction of band gap is attributed to the electronic orbit modification effect of impurity element B, P, Ni, Ru in g-C3N4. Ru metal doped g-C3N4 is reduces the barrier of OH bond breakage of CH3OH(reduced from 4.551 eV to 1.530 eV), which is beneficial to the hydrogen-producing reaction of AB alcoholysis. The construction and design of a new bifunctional catalyst(photocatalysis and metal catalysis) RuNiB@g-C3N4 is an efficient route in catalyze AB for hydrogen production. The process of molecule NH3BH3, CH3OH and H2O adsorbed on the B-g-C3N4 are exothermic process, the adsorption energy are -1.562 eV, -1.392 eV and -1.443 eV, respectively. AB is preferentially adsorbed on the B-g-C3N4 catalyst, increasing the adsorption energy of CH3OH and H2O on B-g-C3N4-based catalysts is beneficial to the hydrogen production from AB. The study provides a theoretical method for the research on the technology of the coupling of metal catalysis/photocatalysis ammonia borane to produce hydrogen.

Pomegranate-like structured FeNi-nanodots@FeNi LDH composite as a high performance bifunctional catalyst for oxygen electrocatalytic reactions in zinc-air batteries

An efficient bifunctional oxygen catalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for the widespread application of rechargeable zinc-air batteries (ZABs) with high energy density and low-cost electrically. Herein, we report an effective pomegranate-like structured FeNi–N–C@FeNi LDH catalyst using Zeolitic Imidazolate Framework (ZIF-8) as precursor via pyrolysis and hydrothermal reactions. The as-prepared FeNi–N–C@FeNi LDH composite, consisting of FeNi-nanodots embedded in carbon matrix and metal layered double hydroxides (LDHs) as outer layer, exhibits preferable performance toward ORR (E1/2 = 0.890V) and OER (Ej = 10 = 1.535V) compared to precious metal-based catalysts. Moreover, when being applied in ZABs, the FeNi–N–C@FeNi LDH composite displays a high open-circuit voltage of 1.497 V and a durability of up to 100 h, demonstrating its great possibility in practical application.

Integrating PtCo nanoparticles on N, S doped pore carbon nanosheets as high-performance bifunctional catalysts for oxygen reduction and hydrogen evolution reactions

The development of low-Pt bifunctional electrocatalysts with excellent performance for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is critical for the advancement of the hydrogen economy. Here, we have integrated low-loading Pt and Co metals into N, S doped porous carbon nanosheets to obtain composite catalysts encapsulating PtCo alloy nanoparticles (PtCo2@Co9S8/N-CNS and PtCo2@N-CNS). The acquired PtCo nanoparticles, with dimensions of about 2.5 nm, are uniformly distributed and firmly anchored in N, S doped carbon nanosheets with large specific surface areas and rich pore structure, forming multiple active centers and effectively preventing the aggregation of metal nanoparticles. The PtCo2@Co9S8/N-CNS and PtCo2@N-CNS display high ORR catalytic mass activity of 1.65 A mgPt-1 and 1.01 A mgPt-1 in 0.1 M HClO4. The PtCo2@N-CNS catalyst exhibits excellent HER performance in 0.5 M H2SO4, with a mass activity (at 50 mV) 4.3 times higher than that of Pt/C. The PtCo2@Co9S8/N-CNS and PtCo2@N-CNS also exhibit stronger ORR and HER stability than Pt/C after accelerated durability tests. The superior catalytic activity performance of catalysts can be attributed to the synergistic effect of multiple active centers of PtCo, Co9S8 and Co-N in the catalysts. The confinement of PtCo nanoparticles by Co metal and N, S doped porous nanosheets derived from graphitic carbon nitride (g-C3N4) as the template, which can effectively prevent the corrosion and migration of the catalysts under acidic conditions, enhances the catalytic stability of the materials. This study provides a new perspective for the development of economical and efficient bifunctional low-Pt catalysts.

N-doped carbon nanotube encapsulated nZVI as a high-performance bifunctional catalyst for oxidative desulfurization

N-doped carbon nanotube encapsulated nZVI as a high-performance bifunctional catalyst for oxidative desulfurization

Facile construction Co-doped and CeO2 heterostructure modified NiS2 grown on foamed nickel for high-performance bifunctional water electrolysis catalysts

The development of cost-effective non-precious metal bifunctional electrocatalysts with performance comparable to that of precious metal-based catalysts is an important factor in achieving industrial hydrogen production from electrolytic water. In order to prepare electrocatalysts with highly exposed active sites and high intrinsic activity, unique heterostructure and element doped 2D Co–NiS2/CeO2 nanosheets grown on foamed nickel (Co–NiS2/CeO2/NF) are prepared by hydrothermal reaction and annealing. The Co–NiS2/CeO2/NF catalyst demonstrates excellent performance and stability in alkaline solutions. In 1.0 M KOH solution, the overpotentials for the HER and OER were found to be as low as 88 mV and 240 mV, respectively. Moreover, when utilized as both the anode and cathode in a standard two-electrode water electrolyzer, Co–NiS2/CeO2/NF delivers 50 mA cm−2 at a relatively low voltage of 1.82 V and was able to maintain its high performance levels without any degradation even after 48 h of CP test. The combination of doping and interfacial effects greatly increases the number of active sites and the activity of the catalyst. This study provides a new pathway for the design of cost-effective, high-performance catalytic materials for overall water splitting.

Rattle-structured CuO/Co3O4@C microspheres, a potent bifunctional catalyst for hydrogen production from ammonia borane hydrolysis and methanolysis

Engineering and fabricating cost-effective and high-performing bifunctional catalysts for ammonia borane (AB) hydrolysis and methanolysis is paramount for their commercial availability. A series of rattle-structured CuO/Co3O4@C microsphere bifunctional catalysts for AB hydrolysis and methanolysis were produced using a simple hard template etching approach. The CuO/Co3O4@C-4 (4 refers to designed the mole ratio of Cu/Co) exhibits the best activity with TOF of 18.8 and 26.8 molH2·molcat-1·min−1 for AB hydrolysis and methanolysis, respectively. It is discovered that the excellent performance is mainly attributed to its unique rattle structure and the synergetic effect between Co3O4 and CuO. Kinetic isotope effect (KIE) experiments and infrared spectroscopy were applied to investigate AB hydrolysis and methanolysis reaction mechanisms. A suggested mechanism for AB methanolysis on rattle-structured CuO/Co3O4@C-4 is proposed based on the experiment results. This work could provide useful guidance for the construction of high-performance bifunctional catalysts for AB hydrolysis and methanolysis for hydrogen production.

Construction of Co/FeCo@Fe(Co)3O4 heterojunction rich in oxygen vacancies derived from metal–organic frameworks using O2 plasma as a high-performance bifunctional catalyst for rechargeable zinc-air batteries

Developing high-efficient, good-durability, and low-cost bifunctional non-precious metal catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is urgent and significant for promoting the practical rechargeable zinc-air batteries (RZABs). Herein, N-doped carbon coated Co/FeCo@Fe(Co)3O4 heterojunction rich in oxygen vacancies derived from metal–organic frameworks (MOFs) is successfully constructed by O2 plasma treatment. The phase transition of Co/FeCo to FeCo oxide (Fe3O4/Co3O4) mainly occurs on the surface of nanoparticles (NPs) during the O2 plasma treatment, which can form rich oxygen vacancies simultaneously. The fabricated catalyst P-Co3Fe1/NC-700-10 with optimal O2 plasma treatment time of 10 min can reduce the potential gap between the OER and ORR to 760 mV, which is much lower than commercial 20% Pt/C + RuO2 (910 mV). Density functional theory (DFT) calculation indicates that the synergistic coupling between Co/FeCo alloy NPs and FeCo oxide layer can promote the ORR/OER performance. Both liquid electrolyte RZAB and flexible all-solid-state RZAB using P-Co3Fe1/NC-700-10 as the air–cathode catalyst display high power density, specific capacity and excellent stability. This work provides an effective idea for the development of high performance bifunctional electrocatalyst and the application of RZABs.

Rational design of bifunctional hydroxide/sulfide heterostructured catalyst for efficient electrochemical seawater splitting

Heterostructure engineering is one of the most promising strategies for efficient water splitting by electrocatalysts. However, it remains challenging to design heterostructured catalysts to achieve the desired goals in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in seawater splitting. Here, particulate heterostructures of FeCoNi hydroxide/sulfide supported on nickel foams were prepared by hydrothermal methods to achieve a high-performance bifunctional catalyst. The synthesized FeCoNi hydroxide/sulfide exhibited excellent electrocatalytic performance, requiring an overpotential of 195 mV for OER and 76 mV for HER to achieve a current density of 10 mA cm−2 while showing excellent stability. The catalyst maintains its excellent performance even in artificial or natural seawater with high salinity, which is a harsh environment. When applied directly to a water splitting system, the catalyst achieves a current density of 10 mA cm−2 at only 1.5 V (1.57 V in alkaline seawater). The FeCoNi hydroxide/sulfide heterostructure is an excellent electrocatalytic bifunctional catalyst due to compositional modulation, systematic charge transfer optimization, improved intermediates adsorption, and increased electrocatalytic active sites and the synergistic effect of the heterostructure.

Constructing Molybdenum Phosphide@Cobalt Phosphide Heterostructure Nanoarrays on Nickel Foam as a Bifunctional Electrocatalyst for Enhanced Overall Water Splitting.

The construction of multi-level heterostructure materials is an effective way to further the catalytic activity of catalysts. Here, we assembled self-supporting MoS2@Co precursor nanoarrays on the support of nickel foam by coupling the hydrothermal method and electrostatic adsorption method, followed by a low-temperature phosphating strategy to obtain Mo4P3@CoP/NF electrode materials. The construction of the Mo4P3@CoP heterojunction can lead to electron transfer from the Mo4P3 phase to the CoP phase at the phase interface region, thereby optimizing the charge structure of the active sites. Not only that, the introduction of Mo4P3 will make water molecules preferentially adsorb on its surface, which will help to reduce the water molecule decomposition energy barrier of the Mo4P3@CoP heterojunction. Subsequently, H* overflowed to the surface of CoP to generate H2 molecules, which finally showed a lower water molecule decomposition energy barrier and better intermediate adsorption energy. Based on this, the material shows excellent HER/OER dual-functional catalytic performance under alkaline conditions. It only needs 72 mV and 238 mV to reach 10 mA/cm2 for HER and OER, respectively. Meanwhile, in a two-electrode system, only 1.54 V is needed to reach 10 mA/cm2, which is even better than the commercial RuO2/NF||Pt/C/NF electrode pair. In addition, the unique self-supporting structure design ensures unimpeded electron transmission between the loaded nanoarray and the conductive substrate. The loose porous surface design is not only conducive to the full exposure of more catalytic sites on the surface but also facilitates the smooth escape of gas after production so as to improve the utilization rate of active sites. This work has important guiding significance for the design and development of high-performance bifunctional electrolytic water catalysts.