Unassisted overall water splitting with a solar‐to‐hydrogen efficiency of over 10% by coupled lead halide perovskite photoelectrodes

Hydrogen is a promising future sustainable fuel candidate with boundless opportunities. Research into photoelectrochemical (PEC) water splitting based on a lead halide perovskite (LHP) has progressed significantly with the aim of more efficient solar hydrogen production. Herein, we unite a well‐known photo‐absorbing LHP with cost‐effective water‐splitting catalysts, and we introduce two types of monolithic LHP‐based PEC devices that act as a photocathode and a photoanode for the hydrogen evolution reaction and oxygen evolution reaction, leading to efficient unbiased overall water splitting. Through the integration of these two monolithic LHP‐based photoelectrodes, an unbiased solar‐to‐hydrogen conversion efficiency of 10.64% and a photocurrent density of 8.65 mA cm−2 are achieved. Recently, lead halide perovskite‐based photoelectrochemical water splitting has been developed intensively; however, unbiased lead halide perovskite photoelectrode lack in research. In this article, ultra‐stable coupling of two lead halide perovskites‐based photoelectrodes, solar to the hydrogen conversion efficiency of over 10%, and photocurrent density of 8.65 mA cm−2 are reported.