An anatase/TiO2(B) homojunction loaded with Au nanoparticles was synthesized, achieving a C2H6 yield rate of 170 μmol g-1 h-1 in a flow photoreactor. The homojunction reduces TiO2(B)'s strong oxidative ability, offering a more moderate environment for methane dehydrogenation, while Au aids in charge mitigation and methyl radical coupling. The catalyst highlights homojunction engineering and a ternary synergistic effect in photocatalytic CH4 coupling.