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The precise design and development of high-performing oxygen evolution reaction (OER) for the production of industrial hydrogen gas through water electrolysis has been a widely studied topic. A profound understanding of the nature of electrocatalytic processes reveals that Ni-based catalysts are highly active toward OER that can stably operate at a high current density for a long period of time. Given the current gap between research and applications in industrial water electrolysis, we have completed a systematic review by constructively discussing the recent progress of Ni-based catalysts for electrocatalytic OER at a large current density, with special focus on the morphology and composition regulation of Ni-based electrocatalysts for achieving extraordinary OER performance. This review will facilitate future research toward rationally designing next-generation OER electrocatalysts that can meet industrial demands, thereby promoting new sustainable solutions for energy shortage and environment issues. [ABSTRACT FROM AUTHOR]

Ru-modified NiFe MOF nanosheet array was elaborately designed via self-driven galvanic replacement reaction (GRR), which exhibits dramatically enhanced HER, OER and UOR catalytic property as a multifunctional electrocatalyst. [Display omitted] • Ru-modified NiFe MOF nanosheet array was designed via self-driven galvanic replacement reaction. • Enhanced catalytic potency benefitted from spontaneous electronic reconstruction in the interface. • The Ru-NiFe- x /NF are endowed with richer high-valence Ni active species. • The Ru-NiFe- x /NF can operate as multifunctional electrocatalyst with high current density. Urea electro-oxidation reaction (UOR) has been a promising strategy to replace oxygen evolution reaction (OER) by urea-mediated water splitting for hydrogen production. Naturally, rational design of high-efficiency and multifunctional electrocatalyst towards UOR and hydrogen evolution reaction (HER) is of vital significance, but still a grand challenge. Herein, an innovative 3D Ru-modified NiFe metal-organic framework (MOF) nanoflake array on Ni foam (Ru-NiFe- x /NF) was elaborately designed via spontaneous galvanic replacement reaction (GRR). Notably, the adsorption capability of intermediate species (H*) of catalyst is significantly optimized by Ru modification. Meanwhile, rich high-valence Ni active species can be acquired by self-driven electronic reconstruction in the interface, then dramatically accelerating the electrolysis of water and urea. Remarkably, the optimized Ru-NiFe-③/NF (1.6 at% of Ru) only requires the overpotential of 90 and 310 mV to attain 100 mA cm−2 toward HER and OER in alkaline electrolyte, respectively. Impressively, an ultralow voltage of 1.47 V is required for Ru-NiFe-③/NF to deliver a current density of 100 mA cm−2 in urea-assisted electrolysis cell with superior stability, which is 190 mV lower than that of Pt/C-NF||RuO 2 /NF couple. This work is desired to explore a facile way to exploit environmentally-friendly energy by coupling hydrogen evolution with urea-rich sewage disposal. [ABSTRACT FROM AUTHOR]

[Display omitted] • A MOF mediated method has been proposed for the synthesis of (Ru-Co)O x nanobox. • The (Ru-Co)O x nanoboxes are endowed with rich vacancies and interfaces. • The doping of ultralow Ru effectively modifies the electronic structure of CoO x. • (Ru-Co)O x nanoboxes could deliver outstanding electrocatalytic OER performance. For accelerating the reaction kinetics of oxygen evolution reaction (OER) and improving the efficiency of water electrolysis, it is essential to develop high-performance and robust OER electrocatalysts. Herein, heterostructured ruthenium-cobalt oxide hollow nanoboxes are developed for enabling a highly efficient OER electrocatalysis. Benefitting from the desirable structural and compositional merits of more exposure of surface active centers, modulated electronic structure, and interfacial synergy effect, the (Ru-Co)O x hollow nanobox could exhibit excellent electrocatalytic performance toward OER. Particularly, an extremely low overpotential of 265 mV is necessary for the optimized (Ru-Co)O x -350 to achieve a current density of 10 mA cm−2, together with a small Tafel slope of 60 mV dec-1. More interestingly, by combing (Ru-Co)O x -350 with Pt/C for driving alkaline water splitting, an ultralow cell voltage of merely 1.57 V is required. [ABSTRACT FROM AUTHOR]