Visible light assisted highly efficient hydrogen production from H2S decomposition by CuGaO2 and CuGa1−xInxO2 delafossite oxides bearing nanostructured co-catalysts

The present communication is the report of our research work on synthesis of new delafossite oxides containing Ga/Ga and In p-block elements, and their visible light driven catalytic activity in solar H2 production from H2S decomposition. CuGaO2 and its indium doped analogue CuGa1−xInxO2 (x = 0.065) delafossite oxides without/with NiO and RuO2 co-catalysts loading in nanostructures were prepared by solid state reaction method. These materials possess hexagonal rhombohedral structure (XRD); morphologically CuGaO2 has irregularly-shaped plate like particles while all others have ordered hexagonal rod-like arrangements (FESEM). Co-catalyst deposits of few nm sizes are observable as white spots/patches on the surface of naked oxide catalysts. Acquiring p-type conductivity from the mixed valence of Cu (+1 and +2) and oxygen deficiency, these catalysts strongly absorb visible light (Eg = 1.85 eV) in a wide wavelength range. They decompose H2S in aqueous 0.5 M KOH solution under visible light (λ ⩾ 420 nm) irradiation and generate H2 to the tune of 4300 μmol/h, giving rise to a high quantum efficiency of 13.6% at 550 nm. The exceedingly higher rate of H2 production appears to result from a combined contribution of chemical nature (p-block elements Ga and In), p-type conductivity and an efficient e−–h+ separation.