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[Display omitted] Combining interfacial oxygen vacancy engineering with a built-in electric field (BEF) technique is an efficient way to build efficient and practical electrocatalytic water-splitting catalysts. In this study, a Fe 3 O 4 -FeSe 2 heterojunction catalyst with oxygen vacancies supported on reduced graphene oxide (rGO) was designed and successfully fabricated using a simple two-step hydrothermal method. Owing to the different Fermi levels of Fe 3 O 4 and FeSe 2 , a BEF was generated at the interface, which enhanced the separation of negative and positive charges, thus optimizing the adsorption of hydrogen/oxygen intermediates on the heterostructures and improving the activity of the catalyst. Experimental results show that Fe 3 O 4 -FeSe 2 /rGO/NF exhibits excellent hydrogen and oxygen evolution performances, with low overpotentials of 234/300 mV at 100 mA⋅cm−2. A water electrolyzer assembled with Fe 3 O 4 -FeSe 2 /rGO/NF as both the anode and cathode requires only a small potential of 1.78 V to reach a current density of 100 mA⋅cm−1. This study provides an innovative approach for constructing a catalyst with excellent electrocatalytic performance for overall water splitting. [ABSTRACT FROM AUTHOR]

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–NiS 2 /CeO 2 nanosheets grown on foamed nickel (Co–NiS 2 /CeO 2 /NF) are prepared by hydrothermal reaction and annealing. The Co–NiS 2 /CeO 2 /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–NiS 2 /CeO 2 /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. Co-doped and CeO 2 heterostructure modified NiS 2 grown on foamed nickel electrocatalyst is successfully constructed through a simple hydrothermal process followed by further vulcanization treatment and exhibits excellent electrocatalytic performance and stability towards overall water splitting. In 1.0 M KOH solution, the current densities of the HER and OER can reach 10 mA cm−2 with minimum overpotentials of 88 mV and 240 mV, respectively. Additionally, when a standard two-electrode water electrolyzer is fabricated by employing Co–NiS 2 /CeO 2 /NF as both the cathode and anode, it can generate 10 mA cm−2 at 1.38 V and operate steadily without performance degradation after 48 h. [Display omitted] • The combination of doping and interfacial effects greatly increases the activity of the catalyst. • Co–NiS 2 /CeO 2 /NF exhibits excellent activity towards overall water splitting. • Co–NiS 2 /CeO 2 /NF shows a remarkably stability with a nearly unchanged potential after a longer stability test. [ABSTRACT FROM AUTHOR]

[Display omitted] Designing heterojunction catalysts with energy effects at the interface, particularly combining the surface structure advantages of super-hydrophilic interfaces with the high activity advantages of bimetal synergistic optimisation, is the key to developing economical and efficient industrial electrocatalytic water-splitting catalysts. In this study, a coupled nanoflower-like NiFe(OH) x /(Ni, Fe)Se heterostructure catalyst supported on Ni foam (NF) (NFSe@NFOH/NF) was designed and successfully prepared using hydrothermal and electrodeposition strategies. Owing to the electron interaction at the heterogeneous amorphous (NFOH)/crystalline (NFSe) interface and the bimetallic synergistic effect of Ni and Fe, the prepared NFSe@NFOH/NF exhibited excellent and stable oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalytic properties, with low overpotentials of 214/276 mV at 100 mA⋅cm−2 and 262/340 mV at 500 mA⋅cm−2. The assembled water electrolyser comprising NFSe@NFOH/NF || NFSe@NFOH/NF needed only small voltages of 1.73 and 1.85 V to yield current densities of 100 and 500 mA⋅cm−2, respectively. This study offers an innovative design idea for the rational adoption of interface engineering and amorphous–crystalline engineering techniques to construct catalysts with excellent catalytic activity and stability for electrocatalytic overall water splitting (EOWS) at a high current density, which further facilitates the advancement of sustainable energy technology in the future. [ABSTRACT FROM AUTHOR]