Here 𝑄 -• is the semiquinone radical and 𝑄 2-is the quinone dianion. On the other hand, BQ is electrooxidized by electrocatalytically generated hydroxyl radicals . Previous works have reported electrooxidation of BQ by metal oxide electrocatalysts, such as tin or lead oxide, at potentials below that of water electrolysis . Intermediate products of BQ electrooxidation include organic acids (e.g., maleic acid) and humic substances (small aromatic polymers), while complete BQ oxidation forms carbon dioxide and water .