CdS nanorods supported copper-nickel hydroxide for hydrogen production under direct sunlight irradiation

Abstract

A series of composite photocatalysts based on CdS nanorods decorated with Cu/Ni hydroxides were prepared via deposition precipitation method at room temperature (total metal loading ≈ 3 wt%). The performance of these photocatalysts was evaluated for H2 production through water dissociation reaction under direct sunlight. The 2.4Cu(OH)20.6Ni(OH)2/CdS photocatalyst with a total 3 wt% nominal metal cocatalyst loading demonstrated an excellent hydrogen production activity of ~20 mmol h−1g−1, that is 2 and 20 times greater than the benchmark Au/CdS and pristine CdS photocatalysts, respectively. Detailed analyses based on UV–Visible diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), steady state photoluminescence (PL) and energy dispersive spectroscopy (EDS) suggested cocatalysts Cu/Ni hydroxides were transformed into their metallic states during photoreaction. Cu° was produced by the transfer of electrons due to the as available position of CdS conduction band (E°=0.61 V) to surface Cu(OH)2 nanoclusters (Cu(OH)2/Cu°, E°= 0.224 V) whereas Ni° was produced by the shift in conduction band level of CdS under continuous sunlight illumination (Ni(OH)2/Ni°, E°= 0.72 V). Based on these observations, the mechanism of hydrogen production from water splitting over Cu/Ni(hydroxides)-CdS was described.