Electrochemical synthesis of hydrogen peroxide from water and oxygen

H₂O₂ is important in large-scale industrial processes and smaller on-site activities. The present industrial route to H₂O₂ involves hydrogenation of an anthraquinone and O₂ oxidation of the resulting dihydroanthraquinone — a costly method and one that is impractical for routine on-site use. Electrosynthesis of H₂O₂ is cost-effective and applicable on both large and small scales. This Review describes methods to design and assess electrode materials for H₂O₂ electrosynthesis. H₂O₂ can be prepared by oxidizing H₂O at efficient anodic catalysts such as those based on BiVO₄. Alternatively, H₂O₂ forms by partially reducing O₂ at cathodes featuring either noble metal alloys or doped carbon. In addition to the catalyst materials used, one must also consider the form and geometry of the electrodes and the type of reactor in order to strike a balance between properties such as mass transport and electroactive area, both of which substantially affect both the selectivity and rate of reaction. Research into catalyst materials and reactor designs is arguably quite mature, such that the future of H₂O₂ electrosynthesis will instead depend on the design of complete and efficient electrosynthesis systems, in which the complementary properties of the catalysts and the reactor lead to optimal selectivity and overall yield.