Water Oxidation to Hydrogen Peroxide on Carbonaceous Materials

Abstract

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 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.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.