Steering Hole Transfer from the Light Absorber to Oxygen Evolution Sites for Photocatalytic Overall Water Splitting

Harvesting solar energy to realize water splitting into H₂ and O₂ in 2:1 stoichiometric without using any sacrificial agents and external bias confronts a big challenge. Herein, the authors demonstrate that engineering the hole transfer kinetic by embedding reduced graphene oxide (rGO) in the interface of light absorber (2D carbon nitride, 2D g-CN) and oxygen evolution cocatalysts (MO_x, M = Fe, Co, Ni) can both tune the hole extraction rate and oxygen evolution performance. As a result of breaking the rate-determining step (i.e., oxygen evolution reaction) in overall water splitting, the optimal Pt/2D g-CN/rGO-FeO_x photocatalyst can evolve H₂ and O₂ in pure water with the rates of 14.07 and 7.03 µmol h⁻¹, respectively, showing roughly higher gas evolution rates and also excellent stability compared to the photocatalysts without hole transport engineering. This work reveals the feasibility of overall water splitting by tuning the oxygen evolution dynamic and affords a versatile strategy for designing cocatalyst/photocatalyst systems for efficient photocatalysis.