Photocatalytic Overall Water Splitting with a Solar‐to‐Hydrogen Conversion Efficiency Exceeding 2% through Halide Perovskite

Photocatalytic water splitting using semiconductors is a promising approach for converting solar energy to clean energy. However, challenges such as sluggish water oxidation kinetics and limited light absorption of photocatalyst cause low solar‐to‐hydrogen conversion efficiency (STH). Herein, we develop a photocatalytic overall water splitting system using I 3 − /I − as the shuttle redox couple to bridge the H 2 ‐producing half‐reaction with the O 2 ‐producing half‐reaction. The system uses the halide perovskite of benzylammonium lead iodide (PMA 2 PbI 4 , PMA=C 6 H 5 CH 2 NH 2 ) loaded with MoS 2 (PMA 2 PbI 4 /MoS 2 ) as the H 2 evolution photocatalyst, and the RuO x ‐loaded WO 3 (WO 3 /RuO x ) as the O 2 evolution photocatalyst, achieving a H 2 /O 2 production in stoichiometric ratio with an excellent STH of 2.07 %. This work provides a detour route for photocatalytic water splitting with the help of I 3 − /I − shuttle redox couple in the halide perovskite HI splitting system and enlightens one to integrate and utilize multi catalytic strategies for solar‐driven water splitting.