The development of noble metal-free catalysts for hydrogen evolution is required for energy applications. In this regard, ternary heterojunction nanocomposites consisting of ZnO nanoparticles anchored on MoS -RGO (RGO=reduced graphene oxide) nanosheets as heterogeneous catalysts show highly efficient photocatalytic H evolution. In the photocatalytic process, the catalyst dispersed in an electrolytic solution (S and SO ions) exhibits an enhanced rate of H evolution, and optimization experiments reveal that ZnO with 4.0 wt % of MoS -RGO nanosheets gives the highest photocatalytic H production of 28.616 mmol h g under sunlight irradiation; approximately 56 times higher than that on bare ZnO and several times higher than those of other ternary photocatalysts. The superior catalytic activity can be attributed to the in situ generation of ZnS, which leads to improved interfacial charge transfer to the MoS cocatalyst and RGO, which has plenty of active sites available for photocatalytic reactions. Recycling experiments also proved the stability of the optimized photocatalyst. In addition, the ternary nanocomposite displayed multifunctional properties for hydrogen evolution activity under electrocatalytic and photoelectrocatalytic conditions owing to the high electrode-electrolyte contact area. Thus, the present work provides very useful insights for the development of inexpensive, multifunctional catalysts without noble metal loading to achieve a high rate of H generation.
An efficient and stable CuO-TiO 2 nanocomposite photocatalyst was synthesized by using the simple molten-salt method. Characterization by HR-TEM confirmed the existence of both TiO 2 and CuO in the nanocomposite, revealing hexagonal TiO 2 nanoparticles (NPs) with average particles size of 23.8 nm. CuO QDs decorated on the TiO 2 surface were in the range of 2.2 to 4.6 nm. Photocatalytic experiments for hydrogen (H 2 ) production were carried out under an LED (λ = 365 nm) lamp and natural solar light. The effect of Cu-loading in CuO-TiO 2 NCs and synthesis time were studied. The optimized CuO-TiO 2 NCs abbreviated as CuT-4 and CuT-3 showed 27.7-and 9.0-fold superior rate of H 2 production compared to pristine TiO 2 NPs under LED and solar irradiation, respectively. At optimal conditions, CuO-TiO 2 NCs demonstrated good photostability for H 2 evolution during 75 h illumination under LED light. The experimental results confirmed the cocatalytic role of CuO for improved H 2 generation by a minimized recombination of excitons.
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