Selective Oxidation of Sulfuric Acid to Peroxydisulfuric Acid on a Tungsten Trioxide Anode

Abstract

AbstractThe mechanisms involved in the oxidation of H2SO4 to peroxydisulfuric acid (H2S2O8) and H2O to O2 on WO3, SnO2, and their interface models were investigated using density functional theory. Regardless of the metal oxide, the free energy changes for the two proton‐coupled electron transfer (PCET) steps of the H2SO4 oxidation mechanism indicated that the first PCET is the rate‐limiting step that requires a greater energy input than the second one. Based on the free energy change in the rate‐limiting step, the WO3 anode with SnO2 was expected to produce electrochemically more H2S2O8 in an aqueous H2SO4 solution than SnO2 only without O2 evolution from H2O. We also experimentally confirmed that the Faraday efficiency of H2S2O8 production using the WO3 anode deposited on a F‐doped SnO2 conductive glass (FTO) with lower applied potential is superior to FTO only.