Ultra‐Fast Mass Transfer System by ∼100% Validated Micro‐Basins for Large‐Scale Photochemical Hydrogen Production

ABSTRACT Achieving large‐scale, efficient, and sustainable hydrogen production via environmentally friendly photocatalysis requires not only effective mass transfer but also excellent operational stability. Conventional particulate photocatalyst systems suffer from inherent limitations in mass transfer, such as disordered charge carrier migration and uncontrolled gas bubble evolution, which collectively hinder hydrogen production efficiency. Here, we present a new mass transfer strategy for large‐scale photochemical hydrogen production, which effectively overcomes intrinsic transport limitations and enables ultra‐fast hydrogen bubble detachment by a coalescence‐induced jumping mechanism. By rationally designing a tunnel‐junction photochemical diode integrated with a micro‐basin array of metallic cocatalysts, we achieved nearly 100% activation of surface catalytic sites, thereby promoting directional charge carrier transport and rapid gas bubble evolution. This design delivers an impressive hydrogen production rate of 177.53 µmol h −1 cm −2 and an apparent quantum yield of 70.7% under 420 nm illumination. An outdoor solar‐driven photocatalytic reactor (25 cm × 25 cm) with a high hydrogen production rate was successfully demonstrated, validating the performance of a full‐scale photocatalyst system. This work demonstrates a large‐scale GaN‐based photochemical hydrogen‐production system and provides a useful structural design strategy for the future development of solar hydrogen‐generation technologies.