H2O2 formation mechanisms on the (1 1 2) and (3 1 0) facets of SnO2 via water oxidation reaction with the participation of Bicarbonate: DFT and experimental Investigations

The H2O2 formation mechanisms on the (1 1 2) and (3 1 0) facets of SnO2 via the water oxidation reaction (WOR) with participation of bicarbonate are investigated by density functional theory calculations and electrochemical measurements. Both computational and experimental results show that H2O2 generation is hindered on the surfaces of SnO2 in the absence of HCO3 species. In contrast, more H2O2 is detected for SnO2 films tested in HCO3− aqueous solution than those measured in non-bicarbonate electrolyte. Nevertheless, our kinetic simulations suggest that the co-adsorption of HCO3 species adjacent to H2O on the (1 1 2) and (3 1 0) surfaces of SnO2 do not effectively promote the two-electron WOR to form H2O2. Considering that the H2O2 production scales linearly with the concentration of HCO3−, bicarbonate is likely to directly participate in the process of H2O2 generation as a catalytic medium. That is, the mechanism that H2O2 is formed through the hydrolyzation of HCO4− that is produced by the peroxidation of HCO3− is likely. Our calculations show that H2O2 is formed through this route on both (1 1 2) and (3 1 0) facets of SnO2. In addition, the (1 1 2) surface of SnO2 is kinetically favored for H2O2 generation compared to the (3 1 0) facet.