Hydrogen peroxide (H₂O₂) is one of the most important chemicals used in the chemical industry. It has been widely utilized in pulp and paper manufacturing, chemical synthesis, wastewater management, and disinfection.¹ The primary industrial approach to producing H₂O₂ is via the fossil-based anthraquinone process - an energy-demanding multi-step process requiring high-cost catalysts and generating substantial volumes of waste. Another route to the classic anthraquinone process is the electrochemical production of H₂O₂ from oxygen (O₂) and water (H₂O). This electrochemical route based on renewable energy is an appealing “green” alternative.

Our research group has been extensively working on the electrochemical production of H₂O₂ through anodic water oxidation using various electrode materials, including metal oxides, commercial carbon materials, and boron-doped diamond (BDD). Besides the electrode material, a suitable electrolyte is equally essential to achieve high H₂O₂ concentrations and production rates. The role of carbonate ions (HCO₃^- and CO₃^2-) for producing H₂O₂ has been investigated using commercial carbon fiber paper (CFP). The electrolyte pH was correlated with the activity of CO₃^2- ions in enhancing H₂O₂ production. Thereby, a cyclic mechanism of H₂O₂ generation involving the oxidation of CO₃^2- ions to peroxodicarbonate (C₂O₆^2-) species has been proposed.²

The role of the CO₃^2- ions in enhancing the anodic H₂O₂ production was further studied in a continuous flow reactor using BDD anodes. The flow rate and setup configuration for 2e^- water oxidation to H₂O₂ have been optimized at current densities up to 700 mA cm^-2, with an impressive H₂O₂ production rate and faradaic efficiency. Additionally, the role of a chemical stabilizer in avoiding the H₂O₂ decomposition in the flow system has been addressed. The importance of electrolyte composition, pH, operating parameters, and cell setup to enhance the production of H₂O₂ at the anode was shown. Finally, outstanding H₂O₂ yields were obtained in continuous flow for at least 30 hours.

References

1. Perry, S. C.; Pangotra, D.; Vieira, L.; Csepei, L.-I.; Sieber, V.; Wang, L.; Ponce de León, C.; Walsh, F. C., Electrochemical synthesis of hydrogen peroxide from water and oxygen. Nat. Rev. Chem. 2019, 3 (7), 442-458.
2. Pangotra, D.; Csepei, L.-I.; Roth, A.; Ponce de León, C.; Sieber, V.; Vieira, L., Anodic production of hydrogen peroxide using commercial carbon materials. Appl. Catal. B Environ. 2022, 303, 120848.