Hydrogen production by water electrolysis faces challenges such as high over-potential of oxygen evolution reaction (OER), low economic value of oxygen, and generation of harmful reactive oxygen species (ROS). In recent years, replacing OER with the oxidation of organic small molecules to construct hybrid electrolysis systems coupled with hydrogen evolution reaction (HER) has emerged as a key strategy for achieving low-energy-consumption of high-value-added chemicals and H₂ production. This review systematically summarized the reaction mechanisms, catalyst design strategies, and research progress of our group and other researchers in recent three years on alternative oxidation reactions, such as urea, hydrazine, ammonia, alcohols, and biomass platform molecules, in water electrolysis for H₂ production. This approach not only significantly reduces energy consumption and improves H₂ purity, but also enables the simultaneous synthesis of high-value chemicals or wastewater treatment, offering advantages in energy, environment, and economy. We also discussed the key issues that need to be addressed in the future, providing directional guidance for advancing the sustainable development of hybrid water electrolysis technology and the green production of high-value-added chemicals.

The unavailability of high-performance and cost-effective electrocatalysts has impeded the large-scale deployment of alkaline water electrolyzers. Professor Zidong Wei's group has focused on resolving critical challenges in industrial alkaline electrolysis, particularly elucidating hydrogen and oxygen evolution reaction (HER/OER) mechanisms while addressing the persistent activity-stability trade-off. This review summarizes their decade-long progress in developing advanced electrodes, analyzing the origins of sluggish alkaline HER kinetics and OER stability limitations. Professor Wei proposes a unifying "12345 Principle" as an optimization framework. For HER electrocatalysts, they have identified that metal/metal oxide interfaces create synergistic "chimney effect" and "local electric field enhancement effect", enhancing selective intermediate adsorption, interfacial water enrichment/reorientation, and mass transport under industrial high-polarization conditions. Regarding OER, innovative strategies, including dual-ligand synergistic modulation, lattice oxygen suppression, and self-repairing surface construction, are demonstrated to balance oxygen species adsorption, optimize spin states, and dynamically reinforce metal-oxygen bonds for concurrent activity-stability enhancement. The review concludes by addressing remaining challenges in long-term industrial durability and suggesting future research priorities.

Two major challenges, high cost and short lifespan, have been hindering the commercialization process of lowtemperature fuel cells. Professor Wei's group has been focusing on decreasing cathode Pt loadings without losses of activity and durability, and their research advances in this area over the past three decades are briefly reviewed herein. Regarding the Pt-based catalysts and the low Pt usage, they have firstly tried to clarify the degradation mechanism of Pt/C catalysts, and then demonstrated that the activity and stability could be improved by three strategies: regulating the nanostructures of the active sites, enhancing the effects of support materials, and optimizing structures of the three-phase boundary. For Pt-free catalysts, especially carbon-based ones, several strategies that they proposed to enhance the activity of nitrogen-/heteroatom-doped carbon catalysts are firstly presented. Then, an indepth understanding of the degradation mechanism for carbon-based catalysts is discussed, and followed by the corresponding stability enhancement strategies. Also, the carbon-based electrode at the micrometer-scale, faces the challenges such as low active-site density, thick catalytic layer, and the effect of hydrogen peroxide, which require rational structure design for the integral cathodic electrode. This review finally gives a brief conclusion and outlook about the low cost and long lifespan of cathodic oxygen reduction catalysts.