TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios. N2O photocatalytic decomposition under UVC and UVA irradiation. Heterojunction on the TiO2/g-C3N4 interface play an important role. Optimal ratio of TiO2:g-C3N4 was 1:2 for the highest activity at UVA irradiation.