Boosting photocatalytic water vapor splitting by the integration of porous g-C3N4 and carbonized melamine foam

We report a photothermally-induced liquid-solid/gas-solid-decoupling photocatalytic water-splitting system, where a carbonized melamine foam (CMF) and a porous g-C₃N₄ (PCN) serve as the photothermal substrate and model photocatalyst, respectively. Specifically, liquid water is transformed into the gaseous phase over the CMF due to the photothermal effect, and the generated vapor can be split into hydrogen by PCN via the photocatalysis. This unique biphasic photocatalytic system exhibits a high hydrogen production rate of 368.1 µmol h⁻¹, which is 2.4 and 25.6 times larger than those of the traditional triphasic PCN system (151.7 µmol h⁻¹) and g-C₃N₄ (CN) system (14.4 µmol h⁻¹), respectively. The improved photocatalytic performance is mainly attributed to the optimized energy and mass transfer at the gas-liquid-solid reaction interface, where gas products are rapidly desorbed in the photocatalytic process. This work provides a novel strategy to enhance the photocatalytic performance from the perspectives of energy and mass flow.