Efficient Renewable-to-Hydrogen Conversion via Decoupled Electrochemical Water Splitting

Summary

Water electrolysis powered by renewables provides a green approach to hydrogen production to support the “hydrogen economy.” However, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are tightly coupled in both time and space in traditional water electrolysis, which brings inherent operational challenges, such as the mixture of H₂/O₂ and the limited HER rate caused by the sluggish kinetics of OER. Against this background, decoupling H₂ and O₂ production in water electrolysis by using the auxiliary redox mediator was first proposed in 2013, in which O₂ and H₂ are produced at different times, rates, and/or locations. The decoupling strategy offers not only a new way to facilitate renewables to H_2, but it can also be applied in other chemical or electrochemical processes. This review describes recent efforts to develop high-performance redox mediators, optimized strategies in decoupled water electrolysis, the design of electrolyzer configuration, the challenges faced, and the prospective directions.