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This review summarizes the evaluation, design, and modification strategies of self-supported electrocatalysts, as well as the alternative reactions to replace oxygen evolution reaction at anode for electrocatalytic water splitting with lower energy consumption. [Display omitted] • Transition metal (TM) based self-supported electrocatalysts own potential as anode for hydrogen production at large current density. • The preparation methods of TM-based self-supported electrocatalysts are reviewed and compared. • The strategies to improve the intrinsic activity of catalysts for oxygen evolution reaction (OER) at anode are reviewed. • The challenges and outlooks of TM-based self-supported electrocatalysts as anode for water splitting are described. Hydrogen produced from water electrolysis is a promising alternative to fossil fuels. The oxygen evolution reaction (OER), which occurs at the anode, involves a four-electron transfer process and requires a large potential to overcome the energy barrier. To address this challenge and reduce the cost associated with noble-metal catalysts, transition metal (TM) based catalysts offer a cost-effective solution. Compared to powder catalysts, TM-based catalysts in situ grown on conductive substrates are more suitable for industrial hydrogen production at large current density. Additionally, oxidation reactions with lower thermodynamic potential than OER have been explored as alternatives to reduce power consumption in electrohydrolysis hydrogen production. In this review, we provide an overview of the evaluation criterion, selection of substrate, preparation methods for self-supporting catalysts and their respective advantages and disadvantages. We also discuss the principle of active site selection and various strategies for enhancing the activity of catalysts, including metal doping, heteroatom doping, co-doping of both, heterojunctions, amorphization, compositing with conductive materials, morphology engineering, and creating superhydrophilic and superaerophobic surface. We then examine alternative anode reactions, such as urea oxidation, hydrazine oxidation, glucose oxidation and alcohol oxidation reactions. Finally, we outline the current challenges in the design of electrocatalysts and anodic oxidation reactions and provide an outlook on the future of hydrogen production using TM-based self-supported electrocatalysts. [ABSTRACT FROM AUTHOR]

Current OER electrocatalysts are hardly applicable for industrial use, which demands high current density (≥ 1000 mA cm-2) at low overpotential (≤ 300 mV) with long-term stability (≥ 100 h). Herein self-supported heterojunction catalyst, NiCo-OH@Ni x Fe y O 4 on Fe foam (FF), is in situ synthesized using two-step corrosion engineering. It only requires an overpotential 275 mV to drive the current density of 1000 mA cm-2 with good long-term stability. Theoretical calculations reveal that such good performance is attributable to electron transfer from NiCo-OH to Ni x Fe y O 4 which weakens the adsorption energy of reaction intermediate (OOH*) to promote the release of O 2 and lowers the free energy barriers for the reaction. Furthermore, a water splitting cell with NiCo-OH@Ni x Fe y O 4 /FF as anode and CoP@FeP/FF as cathode demonstrates its potential for industrial application. The study presents a general strategy for in situ synthesis of heterojunction catalysts on metal foams using controlled corrosion engineering for various catalytic applications. [Display omitted] • NiCo-OH@Ni x Fe y O 4 heterojunction in situ grown on Fe Foam by corrosion engineering. • NiCo-OH@Ni x Fe y O 4 /FF shows great OER activity (j 1000 =275 mV) with long-term stability. • Regulated d-band center of metal site optimizes binding energy of intermediates. • DFT confirms lower ∆G of rate-determined step due to charge transfer at interface. • NiCo-OH@Ni x Fe y O 4 /FF is an excellent anode for industrial water splitting. [ABSTRACT FROM AUTHOR]