Enhanced generation of reactive oxygen species under visible light irradiation by adjusting the exposed facet of FeWO4 nanosheets to activate oxalic acid for organic pollutant removal and Cr(VI) reduction.

Abstract

In this work, taking FeWO4 nanosheets as an example, the activation of oxalic acid (OA) based on facet engineering for the enhanced and stable generation of active radical species is reported, revealing unprecedented surface Fenton activity for pollutant degradation. Density functional theory (DFT) calculations confirmed the more efficient generation of reactive oxygen species over FeWO4 nanosheets with the {001} facet exposed (FWO-001) under visible light irradiation compared to the efficiency of FeWO4 nanosheets with the {010} facet exposed (FWO-010), which could be attributed to a higher density of iron and faster adsorption and activation of OA. The produced •OH tended to diffuse away from the {001} facet of FeWO4 into solution for pollutant redox reactions but preferred to remain on the {010} facet of FeWO4. The slow diffusion of •OH away from the {010} facet of FeWO4 limited its reactivity with the pollutants. Additionally, the generation of •CO2- endowed FeWO4 with a strong reduction ability. Compared with FWO-010, FWO-001 exhibited enhanced redox activity for the catalytic degradation of organic pollutants and Cr(Ⅳ) in the optimized conditions. These findings can help in understanding the facet dependent surface Fenton chemistry of catalytic redox reactions and in designing high-efficient catalysts for environmental decontamination.