Enhanced visible-light photocatalytic conversion of biomass by calcination of Ir-doped SnO₂ nanoparticles with a narrowed bandgap using NaBH₄

Abstract

SnO2 nanoparticles (NPs) exhibit a photocatalytic activity under UV light. However, their limited response to visible light restricts their applications, highlighting the need for new methodologies. We demonstrate Ir-doping to SnO2 only show a slight increase to visible light response and photocatalytic activity. However, treating the Ir-doped SnO2 with NaBH4 calcination dramatically improves the visible light response and photocatalytic activity. The additional NaBH4-assisted calcination further increased the OV density and narrowed the bandgap of Ir ion-doped SnO2 NPs, enabling visible-light-driven photocatalytic oxidation of 5-hydroxymethylfurfural and toluene. This study provides a novel approach to optimize the defect engineering of SnO2-based catalysts through Ir doping and NaBH4 calcination. The resulting increase in OV density and band structure modification were well demonstrated by spectroscopic analyses and DFT calculations. The optimized catalyst exhibited outstanding performance under visible light irradiation, achieving >90 % HMF and > 75 % toluene photoconversion into 2,5-furandicarboxylic acid and benzaldehyde, respectively, while maintaining excellent recyclability. These findings advance the development of multifunctional catalysts and are expected to inspire the design of next-generation catalysts for sustainable biomass transformation.