Electrocatalysts For Water Splitting Research Articles

Enhanced Electrocatalytic Capacity of Two POM@NH2‐MIL‐101(Fe) Composites for Oxygen Evolution Reaction

AbstractThe development and exploration of efficient bifunctional electrocatalysts for water splitting are in high demand and have garnered significant attention in recent years. Herein, by incorporating the advantages of catalytically active polyoxometalates (POMs) and structural stable metal–organic frameworks (MOFs), two POM@MOFs composite materials, Ni4Mo12@Fe and Co4Mo12@Fe, have been successfully prepared via the encapsulation of POMs anions, [MoV12O30(μ2‐OH)10H2{NiII4(H2O)12}]∙14H2O (noted as Ni4Mo12) and [MoV12O30(μ2‐OH)10 H2{CoII(H2O)3}4]∙12H2O (noted as Co4Mo12), into the cavities of MOFs NH2‐MIL‐101(Fe), respectively. Compared to each individual components, Ni4Mo12@Fe and Co4Mo12@Fe composites, as heterogeneous electrocatalysts, both showed enhanced electrocatalytic capacities for efficient oxygen evolution reaction (OER) under alkaline conditions with overpotentials of 332.64 mV for Ni4Mo12@Fe and 352.64 mV for Co4Mo12@Fe at 10 mA cm−2. Additionally, the enhanced electrocatalytic capacities of these two composites could also achieve towards hydrogen evolution reaction (HER). Such a POMs‐assisted strategy for the formation of POM@MOFs composites, described here, paves a new avenue for the development of highly economical, active nonnoble metal bifunctional electrocatalysts for OER and HER.

CeO2‐Accelerated Surface Reconstruction of CoSe2 Nanoneedle Forms Active CeO2@CoOOH Interface to Boost Oxygen Evolution Reaction for Water Splitting

AbstractInterface engineering is an efficient strategy to create high‐performance electrocatalysts for water splitting. In the present work, CeO2@CoSe2 nanoneedle on carbon cloth (CeO2@CoSe2/CC) demonstrates high efficiency for oxygen evolution reaction (OER) and water splitting. CeO2 with abundant O vacancies facilitates the adsorption of OH− and boosts the reconstruction of CoSe2 into CoOOH at lower potentials. The in situ generated active CeO2@CoOOH heterointerface upshifts the d‐band center of Co site, thereby decreasing the free energy of rate‐determining step (RDS) (*O to *OOH) during the OER process. It delivers a low OER overpotential of 245 mV at 10 mA cm−2. CeO2@CoSe2/CC is also found to be active for hydrogen evolution reaction (HER, 138 mV overpotential at 10 mA cm−2), profiting from CeO2‐facilitated *H2O dissociation and *H adsorption on CoSe2. The overall water splitting is achieved over the CeO2@CoSe2/CC bifunctional electrode with a low electrolysis voltage of 1.54 V at 10 mA cm−2. This work offers valuable insights into CeO2‐assisted surface reconstruction as well as provides water electrolysis catalysts through interface engineering.

Defect Passivation of Mn2+-Doped CsPbX3(X=Cl,Br) Perovskite Nanocrystals as Electrocatalyst for Overall Water Splitting.

Mn doping has been used to improve the physical chemistry of lead halide perovskite nanocrystals such as CsPbX3, where X is a halogen ion. In this paper, a two-phase method for Mn-doped CsPbX3 nanosheets (where X=Br, Cl), namely water-hexane system, is reported. Compared to conventional catalyst arrays, the band gap of CsPbBr3 nanocrystalline is easily tuned, the carrier diffusion distance is remote, the band edge position of the band structure is favorable for a wide range of electrocatalytic redox reactions, and the catalytic active site is maximally exposed, providing a larger electrolyte contact area. The porous hierarchical structure also accelerates the release of hydrogen bubbles. The results showed that the optimized Mn : CsPbBr3 catalyst exhibited excellent electrolytic performance of aquatic hydrogen in alkaline electrolyte (1 mol/L KOH). The overpotentials of the oxygen evolution reaction (OER) at the current densities of 10 and 100 mA cm-2 are only 114.4 and 505.4 mV, respectively, with a Tafel slope of 43 mV dec-1. At a current density of 10 mA cm-2, the excess potential required for the hydrogen evolution reaction (HER) is 158.6 mV and it exhibits excellent electrochemical stability. The Mn : CsPbBr3 nanocrystalline consists of two electrodes for hydrolysis of water, requiring only a voltage of 1.45 V. This provides implications for the optimization of electrocatalysts in alkaline electrolytes with the aim of developing next generation 2D electrocatalysts for overall water splitting.

N/S‐codoped Nickel oxide supported on activated Montmorillonite clay as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Developing low‐cost, highly effective, and durable electrocatalysts for complete water splitting (OER/HER) is crucial for future energy provision. Herein, we report N/S‐codoped Nickel oxide supported on activated Montmorillonite clay as an efficient bifunctional electrocatalyst for water electrolysis. The different wt% of Ni‐MMT catalysts were synthesized using an effortless one‐step solvothermal method and their phase recognition, morphology, analysis of elements, and electrochemical performance were confirmed by various characterization techniques. The optimal 10 Ni‐MMT catalyst exhibits outstanding efficiency in both HER (170 mV) and OER (365 mV) at a current density of 10 mAcm‐2 in 1M KOH. Furthermore, doping of N/S heteroatoms increases the active sites for HER/OER, facilitates charge transfer and achieves electrochemical stability of 15 h. The Ni‐MMT catalyst achieved an overall water‐splitting performance in 1M KOH, reaching 10 mAcm‐2 at a cell voltage of 1.82 V.

Cr-doped NiFe sulfides nanoplate array: Highly efficient and robust bifunctional electrocatalyst for the overall water splitting and seawater electrolysis

To replace precious metals and reduce production costs for large-scale hydrogen production, developing stable, high-performance transition metal electrocatalysts that can be used in a wide range of environments is desirable yet challenging. Herein, a self-supported hybrid catalyst (NiFeCrSx/NF) with high electrocatalytic activity was designed and constructed using conductive nickel foam as a substrate via manipulation of the cation doping ratio of transition metal compounds. Due to the strong coupling synergy between the metal sulfides NiS2, Fe9S11, and Cr2S3, as well as their interaction with the conductive nickel foam (NF), the energy barrier for catalytic reactions is reduced, and the charge transfer rate is enhanced. This significantly improves the hydrogen evolution reaction (HER) performance of NiFeCrSx/NF, achieving a current density of 10 mA cm−2 with an overpotential of just 66 mV. Furthermore, doping with chromium generates different valence states of Cr during the catalytic process, which can synergize with the high-valent Fe and Ni, promoting the formation of oxygen vacancies and enriching the active sites for the oxygen evolution reaction (OER). Consequently, at a current density of 10 mA cm−2 in 1.0 M KOH, the overpotential for OER is only 223 mV for NiFeCrSx/NF. Additionally, the in situ grown of self-supporting nanoflower structure on NiFe-LDH not only provides a large catalytic surface area but also facilitates electrolyte penetration during the catalytic process, endowing NiFeCrSx/NF with high long-term stability. When used as a bifunctional catalyst for overall water splitting, the NiFeCrSx/NF||NiFeCrSx/NF electrolyzer requires only 1.29 V to deliver a current density of 10 mA cm−2. Simultaneously, Cr doping protects the Fe sites by maintaining stable valence states, ensuring high performance and stability of NiFeCrSx/NF, even when it is utilized for seawater splitting. This strategy offers novel concepts for creating catalysts based on non-precious metals that can be utilized in various application scenarios.

Spherical Ru/FeOx composite as a bifunctional electrocatalyst for overall water splitting in neutral media

Electrochemical water splitting stands out as a promising technology for H2 production, due to its simplicity and high energy conversion efficiency. Therefore, it is a key issue to develop and design efficient catalysts for overall water splitting (OWS), especially in neutral media. Herein, the present study presents a stable bifunctional electrocatalyst, namely a spherical structure consisting of ruthenium and iron oxide composite supported on iron foam (Ru/FeOx), which was prepared using a simple two-step process. In 1.0M PBS, the optimized Ru/FeOx-300 demonstrates low overpotentials of 30 and 212mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at 10mAcm-2, respectively. More impressively, Ru/FeOx-300 requires only 1.505V to achieve a current density of 10mAcm-2 and exhibits superior electrochemical stability for 24h in a two-electrode neutral electrolyzer. The outstanding catalytic performance and stability of Ru/FeOx-300 nanospheres for water splitting are attributed to the binder-free integrated structure, the enhanced charge transfer facilitated and the synergistic effect between Ru and FeOx. This study offers a novel approach to the development of high-efficiency electrocatalysts for overall water splitting in neutral media.

Benchmarking overall water splitting performance of heterostructured Fe-doped NiMo/NiCo@NF bifunctional electrocatalyst

The design of high-efficiency and cost-effective electrocatalysts for water splitting has recently received much attention. Herein, a self-supported Fe-doped NiMo/NiCo bifunctional electrocatalyst was synthesized using hydrothermal method on nickel foam (NF) to enhance both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). SEM observations revealed NiCo microspheres arranged in a flower-like structure, with Fe-doped NiMo rods decorating the surface. This electrocatalyst demonstrated impressive HER performance, requiring a low overpotential of 63 mV, versus reversible hydrogen electrode (RHE), at a cathodic current density of -10 mA/cm2, and a small charge transfer resistance (Rct) of 2.43 Ω at -200 mV (RHE). For OER, the synthesized electrocatalyst revealed an excellent activity, with a low overpotential of 151 mV (RHE) to afford an anodic current density of 10 mA/cm2 and a small Rct of 0.43 Ω at 300 mV (RHE). Meanwhile, the Fe-doped NiMo/NiCo@NF electrocatalyst in a two-electrode configuration needed only a cell voltage of 1.53 V to deliver a current density of 10 mA/cm2. Overall, this work disclosed that the combination of NiCo and NiMoFe results in the synthesis of a heterogeneous electrocatalyst that offers high efficiency for water splitting and maintains good stability over 10 h.

Investigation of CuO/ITO Photoelectrode Fabricated by PVD for Efficient Photoelectrochemical Water Splitting and Hydrogen Evolution.

Hydrogen and renewable fuels were generated using cost-effective and efficient electrocatalysts for water splitting. In this work, a CuO-based photocathode is used for the water splitting to generate hydrogen energy by PVD technique. The XRD analysis reveals the deposition of CuO thin film on ITO substrates, which is monoclinic. The XRD and LSV analysis of CuO confirmed the type of semiconductor and observed to be P-type semiconductor. SEM study of CuO confirmed the shape, morphology to be a circular and regular shape. The grain size of deposited CuO thin film was found to be 18 nm. The absorption and transmission of CuO thin film were observed through UV spectroscopy analysis and were found to be better photocatalyst in visible range 415-425 nm. The transmittance of the prepared thin film was noted to be maximum 7.6% in the UV range (280-300 nm). The band gap was also measured employing the Tauc plot and found to be 2.98 eV, which is most favorable for water splitting application. FTIR study showed the stretching, vibration, and the functional group of the deposited CuO thin film; the broad band of stretching of Cu-O in monoclinic CuO was observed at the range of 500-700 cm-1, and further peaks were also noted at the range of 1500-1600 cm-1. The linear sweep voltammetry (LSV) of CuO thin film was calculated in the absence of solar spectra and the presence of solar spectra and observed to be enhanced in current under solar spectra. The solar light to hydrogen emission percentage (STH %) of CuO through LSV was observed to be 2.04% under solar spectra. The low Nyquist curve of blank ITO and CuO-coated ITO substrate via electrochemical impedance spectroscopy (EIS) analysis was observed, which confirmed the enhancement of EIS of CuO-coated ITO. The hydrogen generation rate was also calculated by electrochemical cell and observed to be 5325.21 mol g-1 for 6 h.

Electrocatalytic activities of iron-supported N-doped porous carbon towards the oxygen/hydrogen evolution reaction

Red mud (RM) disposal has been highly apprehensive due to its environmental impact. The aluminum industry produces large amounts of red mud waste annually, and turning it into a value-added product is a key component of sustainable development. This study combines RM with an N-doped porous carbon (biomass precursor) as an effective electrocatalyst for oxygen evolution and hydrogen evolution reactions (OER and HER). One significant obstacle to anion-exchange membrane (AEM) electrolyzer applications is the development of electrocatalysts that do not require noble metals and are both efficient and effective at HER and OER. The synthesized iron-supported (RM-derived) N-doped porous carbon (RMNPC) exhibits excellent catalytic activities with 276 and 191 mV overpotentials at 10 mA cm−2 for OER and HER, respectively. A two-electrode cell system is designed with an RMNPC/NF electrode as anode and cathode, and it necessitates just 1.82 V to realize 10 mA cm−2 and shows outstanding durability. This study presents a low-cost but effective electrocatalyst for water splitting for renewable hydrogen production, achieving the goal of RM recycling and highlighting the potential of porous carbon electrocatalysts.

A binary mixture of ionic liquids as a sustainable electrocatalyst for oxygen evolution reaction

A binary mixture of ionic liquids (BmIL1) has been designed from [C12mim][Br] and [MPIM][HCOO] and used as a green and metal free electrocatalyst for oxygen evolution reaction (OER). BmIL1 was found to possess notable electrochemical stability in an alkaline medium to be used as an electrocatalyst in water splitting. Under alkaline conditions, the overpotential to achieve a current density of 10 mA/cm2 is 0.63 V and the Tafel slope is as small as 53.17 mV dec−1. The electrocatalyst can be stabilized over a glassy carbon electrode without adding any binder. To the best of our knowledge, this is the first report on designing an electrocatalyst for water splitting using ionic liquids without adding any binder. Moreover, the minimal E-factor, 100% atom economy and greater Eco Scale associated with the BmIL1 justifies the sustainable synthesis of the green electrocatalyst.

Effect of cobalt-doped iron oxide as an electrocatalyst for water splitting and photocatalytic hydrogen evolution

Developing cost-effective and efficient electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is a significant challenge for economically viable energy conversion devices, such as electrolyzers, rechargeable metal-air batteries, and regenerative fuel cells. Here, we have synthesized cobalt doped iron oxides (CoFe2O3) with different Co:Fe wt%. Among them, Co[1:3]Fe2O3 catalyst demonstrated outstanding performance and stability positioning it as a standard electrocatalyst for OER and HER, and as a photocatalyst for H2 production. The catalysts were characterized using various techniques, including field emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD), and energy dispersive X-ray spectroscopy (EDS) demonstrating successful application in water electrolysis. Specifically, the onset potentials for OER and HER were 1.63 V/RHE and −0.23 V/RHE, respectively. The overpotential (η) required to achieve 10 mA/cm2 for OER (in alkaline medium) and HER (in acidic medium) was 0.44 and −0.3 V/RHE, respectively. Additionally, the developed OER and HER catalyst exhibited high current and potential stability over a 13-hour period. This approach is considered a promising avenue for making water electrolysis for hydrogen (H2) energy viable by minimizing the energy requirements of the electrolytic process. Similarly, the performance of the fabricated catalyst was also examined for the photocatalytic generation of H2 gas in a photo-reactor. Where the highest generation rate of 97.77 mL. (g.min−1) was recorded for Co[1:3]Fe2O3 as a photocatalyst. As a result, the Co[1:3]Fe2O3 catalyst has the potential to function as both a photocatalyst and an electrocatalyst for water splitting.

Research Progress on Clay‐Based Materials for Electrocatalytic Water Splitting

AbstractClay‐based materials are an emerging family of earth‐abundant and low‐cost inorganic functional materials with an modifiable layered‐structure mode similar to hydroxides. They are considered as competitive electrocatalysts for water splitting due to their variable intra‐layer ions, exchangeable interlayer molecules/ions, and large reaction surfaces, which demonstrate fascinating engineering opportunities at the microscale, mesoscale, and macroscale levels. We systematically summarized the research progress of clay‐based materials by classifying clay‐like compounds, clay‐based composites, and clay‐based derivatives, from the viewpoint of structural geometries towards optimizing functionalities. The design strategies for regulating and optimizing clay‐based materials to meet the requirements of electrocatalysts with excellent activity and stability were outlined through representative examples. In addition, the hydrogen production applications of these clay‐based materials were discussed reasonably including recent advances. Finally, the future perspectives of clay‐based materials for electrocatalytic water splitting were demonstrated.

Quasi-1D Oxides as Electrocatalysts for Water-Splitting: Case Study of Sr9M2Mn5O21 (M = Co, Ni, Cu, Zn).

We have demonstrated that multimetal oxides with a quasi-1D structure can be effective electrocatalysts for water electrolysis. Four materials have been systematically investigated, namely, Sr9Co2Mn5O21, Sr9Ni2Mn5O21, Sr9Cu2Mn5O21, and Sr9Zn2Mn5O21, comprising 1D chains of face-sharing MnO6 octahedra and MO6 trigonal prisms (M = Co, Ni, Cu or Zn), which are held together by strontium ions located between the chains. These materials show a consistent trend in electrocatalytic properties for both half-reactions of water-splitting, i.e., oxygen evolution and hydrogen evolution reactions (OER and HER). In particular, Sr9Ni2Mn5O21 has an outstanding performance for OER, with an overpotential of 0.37 V, which is lower than those of many 3D and 2D oxides, and rivals the activity of noble metal catalysts, such as RuO2. This is important given that the OER is considered the bottleneck of the water-slitting process. Chronopotentiometry studies, combined with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction experiments pre- and post-reaction, indicate that Sr9Ni2Mn5O21 is highly stable and retains its structural integrity upon electrocatalytic reactions. This study highlights the potential of quasi-1D oxides as active electrocatalysts for water-splitting.

Bifunctional Electrocatalyst Enhanced Synergistically by MoS2/Ni3S2 Heterojunctions and Au Nanoparticles for Large‐Current‐Density Overall Water Splitting

AbstractDeveloping transition metal based overall water splitting (OWS) electrocatalysts with high efficiency, low‐cost, large current density, and long‐term stability is crucial for industrial electrolysis of water, but remains a major challenge. In this study, a hierarchical electrocatalyst with MoS2/Ni3S2 heterojunctions and a tiny amount of Au nanoparticles grown on nickel foam (MoS2/Ni3S2‐Au@NF) has been developed by a one‐step hydrothermal method. The heterojunctions and Au nanoparticle decoration induce the electron‐rich interfaces in the catalyst, which facilitate the synergistic adsorption of both OER and HER intermediates. As a result, MoS2/Ni3S2‐Au@NF possesses an excellent bifunctional electrocatalytic performance in 1 M KOH with low HER overpotential (78 mV@10 mA cm−2, 253 mV@500 mA cm−2), low OER overpotential (261 mV@50 mA cm−2, 435 mV@500 mA cm−2), and outstanding cyclical stability and continuous stability, which are superior than typical benchmarks of Pt/C and RuO2. An electrolyzer assembled with the self‐supported MoS2/Ni3S2‐Au@NF electrode also displays excellent OWS activity and stability with a current density beyond 100 mA cm−2. This experiment is responding a potential alternative non‐precious metal electrocatalyst for OWS at industrial settings, and thus promotes the real‐world application of hydrogen energy conversions.

ZnS-zeolitic imidazolate framework nanostructure anchored on Ni nanowires as a bifunctional electrocatalyst for high-efficiency overall water splitting

The design and construction of stable and inexpensive bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) present a challenge in electrocatalytic water splitting. In this study, we utilized zeolitic imidazolate frameworks-8 (ZIF-8) as the precursor to fabricate ZnS-ZIF-8 via facile sulfidation processes. The ZnS-ZIF-8 nanostructures were anchored on the surface of the nickel nanowire (denoted as Ni NWs@ ZnS-ZIF-8 nanocomposite) and their catalytic activity for HER, OER, and overall water splitting were studied. The prepared Ni NWs@ ZnS-ZIF-8 revealed a low overpotentials value of 90 and 260 mV at 10 mA cm−2 for HER and OER in 1.0 M KOH solution, respectively. The alkaline electrolyzer assembled by Ni NWs@ ZnS-ZIF-8 provides a low cell voltage of 1.61 V at 10 mA cm−2 current density to boost the overall water splitting and robust stability for 15 h. The superior electrocatalytic activity of Ni NWs@ ZnS-ZIF-8 is owing to the facile and effective electron transport of Ni NWs, accessible active sites of ZnS-ZIF-8, and as well as the synergistic effect of the nanocomposite structures. This finding presents a viable methodology for synthesizing a proficient noble-metal-free catalyst for energy conversion and storage.

Hierarchical Bifunctional NiO Electrocatalyst: Highly Porous Structure Boosting the Water Splitting Activity.

The development of an efficient, low-cost and earth-abundant electrocatalyst for water splitting is crucial for the production of sustainable hydrogen energy. However their practical applications are largely restricted by their limited synthesis methods, large overpotential and low surface area. Hierarchical materials with a highly porous three-dimensional nanostructure have garnered significant attention due to their exceptional electrocatalytic properties. These hierarchical porous frameworks enable the fast electron transfer, rapid mass transport, and high density of unsaturated metal sites and maximize product selectivity. Here the process involved obtaining monodispersed microrod-shaped Ni(OH)2 through a hydrothermal reaction, followed by a heat treatment to convert it into hierarchical microrod-shaped NiO materials. N2 sorption analysis revealed that the BET surface area increased from 9 to 89 m2/g as a result of the heat treatment. The hierarchical microrod-shaped NiO materials demonstrated outstanding bifunctional electrocatalytic water splitting capabilities, excelling in both HER and OER in basic solution. Overpotential of 347 mV is achieved at 10 mA/cm2 for OER activity, with a Tafel slope of 77 mV/dec. Similarly, overpotential of 488 mV is achieved at 10 mA/cm2 for HER activity, with a Tafel slope of 62 mV/dec.

Computational screening of Group VⅢ@C5N4 single-atom electrocatalysts for overall water splitting

Single-atom catalysts (SACs) have great potential for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) since their high atomic utilization and strong metal–support interactions. Herein, we develop TM@C5N4 (TM = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt) catalysts via embedding Group VⅢ TM in holey C5N4 substrate and further evaluate their electrocatalytic activity using density functional theory (DFT) calculations. Systematical studies indicate that Fe@C5N4, Pd@C5N4 and Ir@C5N4 catalysts all exhibit excellent HER performance, which mainly because of their small ΔGH* values of 0.101 eV, -0.114 eV and 0.070 eV, respectively. In parallel, Rh@C5N4 and Ir@C5N4 possess high OER activity along with low overpotential of 0.50 V, which is superior to the commercial IrO2 catalyst (0.56 V). Obviously, Ir@C5N4 could be utilized as bifunctional electrocatalysts both HER and OER in water splitting. Furthermore, we analyze their correlative catalytic mechanisms using the molecular orbitals. Besides, biaxial strain modulation could effectively regulate the catalytic activity of HER and OER. Particularly, 2 % biaxial tensile strain could bring Ir@C5N4 superb HER/OER catalytic performance. Finally, we anticipate that this strain engineering would provide a new perspective for developing high-performance SACs for water splitting.

α-Bi2Mo3O12: A Dual-Functional Material for Electrocatalytic Water Splitting and Supercapacitor Applications.

This study explores the functionality of α-Bi2Mo3O12 (BMO) as an electrocatalyst for water splitting and its suitability for supercapacitor applications. BMO was synthesized by the solvothermal method and characterized in pre-calcination [BMO (BC)], post-calcination [BMO (AC)], and base-etched forms [BMO (BE)]. Structural analysis confirmed the formation of α-Bi2Mo3O12 with well-defined crystallographic planes. Electrochemical analysis revealed that BMO (AC) exhibited the lowest overpotential for hydrogen evolution reactions (HER) and BMO (BC) exhibited the lowest overpotential for oxygen evolution reactions (OER), indicating its superior electrocatalytic activity. The Tafel slope and electrochemical impedance spectroscopy results confirmed the superior kinetics and charge transfer properties of BMO material. Furthermore, BMO samples demonstrated excellent stability during prolonged chronoamperometry (CA) testing for 12 h. For supercapacitor performances, the BMO (BE) exhibits a superior specific capacitance value of 398 F/g at 2.0 A/g. Thus, the BMO material delivers prominent electrocatalytic activity as well as supercapacitor performance. Overall, this study demonstrates the potentiality of α-Bi2Mo3O12 in different forms as a dual-functional material for efficient energy storage and conversion.

Chemical coupling engineered exceptional overall water splitting of autogenic NiS/FeS/NiFeOOH heterostructure

The commercial application of hydrogen production is heavily subjected to the expensive and complex fabrication of required bifunctional catalysts integrated with good oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) activity. Herein, a simple one-spot hydrothermal technique is advocated to simplify the synthesis of NiS/FeS/NiFeOOH heterostructure (denoted as NiFeS) and achieve exceptional bifunctional electrocatalyst for water splitting. Such NiFeS heterostructure reveals multi-synergistic heterointerfaces with chemical coupling to provide more accessible active sites, regulate electronic structure of the active center and enhance interfacial charge transfer, enabling a significant contribution in improving the catalysis. Therefore, the OER overpotential of NiFeS catalyst is only 249 mV to supply 100 mA cm−2 current density, and the overpotential for HER reaches to 153 mV at 10 mA cm−2. When constructed into a lab-made electrode system, it confirms a remarkable cell voltage of only 1.51 V at 10 mA cm−2 for water splitting, along with an exceptional durability up to 100 h at 100 mA cm−2. This study gives a novel insight into heterostructure engineering for the construction of bifunctional electrocatalysts.

NixB/Mo0.8B3 Nanorods Encapsulated by a Boron‐Rich Amorphous Layer for Universal pH Water Splitting at the Ampere Level

AbstractHeterostructured interfaces are crucial to electrocatalysts for water splitting. Herein, coral‐like multiheterostructured NixB/Mo0.8B3 (NMB) nanorods encapsulated by a boron‐rich amorphous layer are prepared for water splitting. Density‐functional theory (DFT) calculations indicate that the NMB interface adjusts the d‐band center and electronic structure of the molybdenum sites. Owing to the strong electronic coupling between Ni, Mo, and B at the heterojunction, large number of exposed catalytic active sites, as well as the special hydrophilic characteristics endowed by the surrounding amorphous layer, the NMB catalyst exhibits remarkable universal‐pH hydrogen evolution reaction (HER) activity with low overpotentials (η) of 15, 26, and 83 mV to deliver 10 mA cm−2 in basic, acid, and neutral media, respectively, and outstanding oxygen evolution reaction (OER) characteristics in the basic medium with η10 and η500 of 170 and 420 mV, respectively. The unique self‐supporting 3D hierarchical interconnected structure facilitates mass transport thus leading to high mechanical stability for 450 and 200 h in HER and OER at ≈1000 mA cm−2. More importantly, the NMB exhibits excellent performance toward overall‐water electrolysis as a bifunctional catalyst with ultralow cell voltages of 1.45/1.56/1.85 V @ 10/100/1000 mA cm−2, demonstrating the large potential in industrial water splitting applications.