Hydrogen production over CuIn3Se5/WO3 hetero-junction

The hydrogen photo-evolution was successfully achieved over CuIn3Se5/WO3 hetero-junction. CuIn3Se5 powder has been synthesized by fusion technique. The compound crystallizes in the chalcopyrite structure and exhibits n-type conductivity. The optical gap (1.19 eV) was determined from the reflectance diffuse spectrum and the flat band potential (-0.22 V) from the Mott Schottky plot. The small forbidden band and the negative flat band potential make it promising for the solar energy conversion. In aqueous solutions, the material is stabilized by hole consumption involving X2- species (= S2- and S2O3 2-). H2 formation would become thermodynamically easy in alkaline media. The best performance was obtained in S2O3 2- solution (10-2 M, pH∼7) with an evolution rate of 0.54 mL g-1 min-1. The photo activity is ascribed to electrons transfer from the sensitizer CuIn3Se5-Conduction Band (CB), acting as electrons pump, to WO3-CB (-0.4 V VS SCE) resulting in the enhanced water reduction.