Decoupled Water Electrolysis Driven by 1 cm2 Single Perovskite Solar Cell Yielding a Solar‐to‐Hydrogen Efficiency of 14.4 %

Abstract Solar water splitting by photovoltaic (PV) electrolysis is a promising route for sustainable hydrogen production. However, multiple PV cells connected in series are generally required to fulfil the practical electrolytic voltages, which inevitably increases the system complexity and resistance. Decoupled water electrolysis for separate hydrogen and oxygen evolution needs smaller voltage to drive each half‐reaction, which provides a feasibility to achieve the single PV cell driven water electrolysis. Herein, by introducing sodium nickelhexacyanoferrate (NaNiHCF) as the redox mediator, decoupled acid water electrolyzer and amphoteric water electrolyzer were respectively constructed. The required voltages for the hydrogen or oxygen evolution steps matched with the output voltages of the perovskite solar cell (PSC). Impressively, by combining one 1 cm 2 FAPbI 3 ‐based PSC (efficiency: 18.77 %) with the decoupled amphoteric water electrolyzer, a solar‐to‐hydrogen (STH) efficiency of 14.4 % was achieved, which outperformed previously reported PSC‐driven water electrolysis cells.