Here for the first time the design and optimization are presented of a three‐component Au/TiO2–gC3N4 nanocomposite photocatalyst able to efficiently produce H2 from water using very low amounts of sacrificial agents and under visible light irradiation. This enhanced photocatalytic behavior compared to Au/TiO2 and Au/gC3N4 materials is the result of synergetic effects due to high quality assembly and interface between the three components. This optimized nanoscale assembly characterized by simultaneous favorable nanoheterojunction formation between g‐C3N4 and TiO2 semiconductors, as well as AuNPs/gC3N4 and AuNPs/TiO2 junctions, leads to enhanced visible light harvesting, charge separation, and H2 production. This composite photocatalyst yields a high H2 production (350 µmol−1 h−1 gcatalyst−1) under visible light irradiation with minimal amounts of sacrificial agent (≤1 vol%), corresponding to activities much higher than reported so far under comparable conditions.

The atmosphere plays a key role in the polycondensation synthesis and the g-C3N4 structure.