Design of noble metal-free NiTiO3/ZnIn2S4 heterojunction photocatalyst for efficient visible-light-assisted production of H2 and selective synthesis of 2,5-Bis(hydroxymethyl)furan

In this work, the development of noble metal-free NiTiO3/ZnIn2S4 (1:0.25 (S1), 1:0.5 (S2), 1:1 (S3), and 1:2 (S4)) heterojunction photocatalysts possessing optimal band edge positions suitable for efficient production of H2 from water and in situ reduction of biomass derivative, 5-hydroxymethylfurfural (HMF) to value-added 2,5-Bis(hydroxymethyl)furan (BHMF) in the absence of any external reducing agent is presented. The electron microscopy analysis of these heterojunctions revealed that ZnIn2S4 nanosheets are decorated uniformly over the surface of NiTiO3 microrods. Interestingly, heterojunction, S3 having NiTiO3/ZnIn2S4 (1:1) showed the best photocatalytic activity with a high H2 generation rate of 4.43 mmol g-1h-1 which is about eight times higher than that of pure ZnIn2S4. Further, the photocatalytic H2 evolution activity of S3 was coupled with in situ reduction of biomass derivative, HMF to obtain value-added chemical, BHMF with > 99% yield along with 100% selectivity. This high photocatalytic activity of S3 is aided by the Z-scheme heterojunction between NiTiO3 and ZnIn2S4. Moreover, photocatalyst, S3, showed excellent photostability and retained the catalytic activity for several cycles of reuse. Overall, this work represents a unique demonstration of H2 generation and high yield production of an important commodity chemical, BHMF from biomass-derivative and provides a greener path for harvesting solar energy and its conversion to chemical energy.