Efficient photocatalytic H₂ production using visible-light irradiation and (CuAg)_xIn_2xZn_2(1-2x)S₂ photocatalysts with tunable band gaps

The band structures of semiconductor photocatalysts fundamentally determine the photocatalytic activity and the H₂ production from the visible-light-driven water-splitting reaction.We synthesize a suite of multicomponent sulfide photocatalysts, (CuAg) _xIn_2xZn_2(1-2x)S₂ (0≤x≤0.5), with tunable band gaps and small crystallite sizes to produce H₂ using visible-light irradiation. The band gap of the photocatalysts decreases from 3.47 eV to 1.51 eV with the increasing x value. The (CuAg)_0.15In_0.3Zn_1.4S₂ (x = 0.15) photocatalyst yielded the highest photocatalytic activity for H₂ production owing to the broad visible-light absorption range and suitable conduction band potential. Under the optimized reaction conditions, the highest H₂ production rate is 230 μmolm^-2 h^-1 with a visible-light irradiation of 2.7 × 10^-5 einstein cm^-2 s^-1, and the quantum yield reaches 12.8% at 420 ± 5 nm within 24 h. Furthermore, the photocatalytic H₂ production is shown to strongly depend on their band structures, which vary with the elemental ratios and could be analyzed by the Nernst relation.