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

Abstract

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 ZnIn₂S_4. 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.

Keywords: 2,5-Bis(hydroxymethyl)furan; Biomass derivative; Hydroxymethylfurfural; Photocatalytic H(2) production.