Active hydrogen-controlled CO<sub>2</sub>/N<sub>2</sub>/NO<sub>x</sub> electroreduction:From mechanism understanding to catalyst design

The development of renewable-energy-powered electrocatalysis meets the need for the sustainable society. With water as the proton source, it enables efficient production of chemicals and fuels from renewable resources like CO₂, N₂, and NO_x under ambient conditions. Hydrogen generated via water dissociation is a crucial participant in transforming reactants into desired products, but it also serves as a direct source of undesired reactions when in excess. In this review, we first present an overview of the functional mechanisms of active hydrogen in the electroreduction of CO₂/N₂/NO_x. We then introduce a range of methods to enhance our understanding of these mechanisms. Furthermore, a detailed discussion of design strategies aimed at regulating active hydrogen in the reduction of CO₂/N₂/NO_x is provided. Finally, an outlook on the critical challenges remaining in this research area and promising opportunities for future research is considered.