Upconversion assisted BiOI/ZnWO4:Er3+, Tm3+, Yb3+ heterostructures with enhanced visible and near-infrared photocatalytic activities

Abstract

Photocatalytic activities of near-infrared (NIR) photocatalysts can be improved by the formation of heterostructures, and an efficient semiconductor upconversion agent of ZnWO₄:Er³⁺, Tm³⁺, Yb³⁺ (ZWOETY) was applied to synthesize the BiOI/ZWOETY (BOI/ZWOETY) composite with a p–n heterostructure. BOI/ZWOETY displays a flower-like structure, and ZWOETY nanoparticles are found to be dispersed homogeneously throughout the BOI surfaces, which is beneficial for the NIR light harvesting. Due to the upconversion luminescence properties of ZWOETY, NIR light can be upconverted to a wide range of light emissions, including red (658 nm), green (526 and 550 nm), blue (483 nm), violet (410 nm), and UV (367 and 380 nm) light, and all these upconversion emissions can be absorbed by BOI for photocatalysis. Under visible and NIR light irradiation, BOI/ZWOETY shows better photocatalytic activities in the degradation of methyl orange (MO) and salicylic acid (SA), compared to pure BOI and BOI/ZWO. The generation of holes contributes to the MO and SA decomposition greatly, and the upconversion properties and the highly efficient separation of electron–hole pairs are responsible for the enhanced photocatalytic activities in BOI/ZWOETY.