CuO-Cr2O3 core-shell structured co-catalysts on TiO2 for efficient photocatalytic water splitting using direct solar light

Synthesis of core-shell structured CuO-Cr2O3 nanoparticles as co-catalyst to improve the photocatalytic hydrogen evolution performance of TiO2 was demonstrated. The effect of co-catalyst loading on TiO2 and the nature of the reactor was found to be more significant for H-2 production under direct solar light. The formation of 9.3 nm Cr2O3 shell over CuO core in the CuO Cr2O3 nanostructured co-catalyst was confirmed using transmission electron microscopy. A very high H-2 production rate of 82.39 and 70.4 mmol h(-1) g(cat)(-1) was observed with quartz and pyrex reactors under direct solar light of irradiation 96-100 mW/cm(2), respectively. This is almost three times higher than that of bare TiO2 under similar experimental conditions. The core-shell co-catalyst loaded on TiO2 by simple mechanical mixing method which is useful for bulk scale synthesis in practical applications. The observed high H-2 production was explained with plausible mechanism where the synergic effect of CuO Cr2O3 co-catalyst loaded TiO2 surface that reduces the effective charge carriers recombination and impeded backward reaction by the Cr2O3 thin layer. The presence of Cu2+ and absence of Cu+ and metallic Cu was confirmed using XPS analysis. The effect of co-catalyst loading and sacrificial agent concentration on the photocatalytic hydrogen production was also reported. The stability of the CuO Cr2O3 core-shell NPs loaded TiO2 photocatalyst under the direct solar light was examined by continuous cycling for three days and it was found to be 81 and 70% of photocatalyst activity is retained after 3 days in the quartz and pyrex reactor systems, respectively. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.