The slow mass transfer, especially the gas evolution process at the solid-liquid interface in photocatalytic water splitting, restricts the overall efficiency of the hydrogen evolution reaction. Here, we report a novel gas-solid photocatalytic reaction system by decoupling hydrogen generation from a traditional solid-liquid interface. The success relies on annealing commercial melamine sponge (AMS) for effective photothermal conversion that leads to rapid water evaporation. The vapor flows towards the photocatalyst covering the surface of the AMS and is split by the catalyst therein. This liquid-gas/gas-solid coupling system avoids the formation of photocatalytic bubbles at the solid-liquid interface, leading to significantly improved mass transfer and conversion. Utilizing CdS nanorods anchored by highly dispersed nickel atoms/clusters as a model photocatalyst, the highest hydrogen evolution rate from water splitting reaches 686.39 μmol h-1, which is 5.31 times that of the traditional solid-liquid-gas triphase system. The solar-to-hydrogen (STH) efficiency can be up to 2.06%. This study provides a new idea for the design and construction of efficient practical photocatalytic systems.