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

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 UVA365 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 O2· production efficiency. Si-PSAC exhibited effective removal performance for various anionic dyes and endocrine-disrupting chemicals under UVA365 irradiation. Continuous-flow column tests revealed the life span of Si-PSAC under UVA365 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 O2· production can extend commercially-available Si-PSAC into the full-scale photocatalysis.