Unexpected discovery of superoxide radical generation by oxygen vacancies containing biomass derived granular activated carbon

Abstract

l Herein, we discovered and reported oxygen vacancies in silicon oxycarbide containing granular palm shell activated carbon (Si-PSAC) as a photocatalyst under UV irradiation. A strong correlation between the atomic content of Si1+, oxygen vacancies and photocatalytic performance of Si-PSAC was obtained. Based on the electron paramagnetic resonance and photoluminescence analyses, Si-PSAC under UVA(365) irradiation exhibited a higher donor density, better charge transfer and lower electron-hole recombination than that under the other light sources, leading to a higher O-2(center dot-) production efficiency. Si-PSAC exhibited effective removal performance for various anionic dyes and endocrine-disrupting chemicals under UVA(365) irradiation. Continuous-flow column tests revealed the life span of Si-PSAC under UVA(365) irradiation was extended by more than 16-fold compared to adsorption column. Since the oxygen vacancies can be created from the naturally present Si in the biomass derived Si-PSAC during the activation, this unexpected discovery of O-2(center dot-) production can extend commercially-available Si-PSAC into the full-scale photocatalysis. (c) 2020 Elsevier Ltd. All rights reserved.