Alkaline hydrogen oxidation reaction catalysts: fundamental mechanisms, classification, regulation strategies and application

Hydrogen energy represents a clean, high-efficiency secondary energy carrier with zero carbon emissions during utilization. And it is a very promising option for combating global climate change and environmental pollution. However, as a key half-cell reaction in hydrogen fuel cells, enhancing the kinetic activity of the hydrogen oxidation reaction (HOR) remains a challenge at present. In this context, it provides a comprehensive review of HOR mechanism under alkaline conditions and recent strategies for regulating electrocatalysts. Firstly, starting from the discussion of popular theories based on different active descriptors covering double functional theory and hydrogen binding energy theory, the fundamental principles of the alkaline HOR are expounded. Secondly, the types of electrocatalysts currently used for the alkaline HOR reaction are overviewed, and the optimization strategies for high-performance alkaline hydrogen oxidation reaction electrocatalysts are summarized, including atomic doping, geometric effects, and heterostructure construction. Then, the paper also reviews the precious metal and non-precious metal catalyst materials that have been applied to alkaline hydrogen–oxygen fuel cells. Finally, the future research directions for non-Pt electrocatalysts in HOR are outlined.