A Z-scheme ZnIn2S4/Nb2O5 nanocomposite: constructed and used as an efficient bifunctional photocatalyst for H2 evolution and oxidation of 5-hydroxymethylfurfural

A bifunctional ZnIn2S4/Nb2O5 (ZIS/NbO) photocatalyst was constructed by growing Nb2O5 nanospheres on the petals of ZnIn2S4 microspheres via a facile hydrothermal approach. The composite possessed a direct Z-scheme heterostructure that was confirmed by in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and electron spin resonance (ESR) measurements. Owing to the good charge separation efficiency in the Z-scheme system, the lifetime of charge carriers in ZIS/NbO was obviously prolonged. Thus, the rate of hydrogen evolution for optimized ZIS/NbO was 2.8 and 1.8 times higher than that of Nb2O5 and ZnIn2S4, respectively. Furthermore, the ZIS/NbO also showed good performance for the oxidation of biomass-derived intermediate 5-hydroxymethylfurfural (HMF) to value-added products. More importantly, the coupled photocatalytic H-2 reduction and HMF oxidation were achieved on the ZIS/NbO Z-scheme heterostructure at the same time. Due to the presence of a direct Z-scheme heterojunction that prevents the recombination of photogenerated electrons and holes in the composite, the ZIS/NbO displayed excellent photocatalytic performance. Our findings are expected to offer a broad optical window for fabricating bifunctional heterostructured composites for coupled photocatalytic reduction and oxidation.