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

• H 2 O 2 generation is hindered on the surfaces of SnO 2 in the absence of HCO 3 species. • Bicarbonate is likely to directly participate in the process of H 2 O 2 generation as a catalytic medium. • The mechanism that H 2 O 2 is formed through the hydrolyzation of HCO 4 − that is produced by the peroxidation of HCO 3 − is likely. • The (1 1 2) facet of SnO 2 is kinetically favored for H 2 O 2 generation compared to the (3 1 0) facet. • A suitable catalyst for H 2 O 2 production should have an appropriate adsorption for HCO 3 − and an effective catalytic ability for the peroxidation of HCO 3 − . The H 2 O 2 formation mechanisms on the (1 1 2) and (3 1 0) facets of SnO 2 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 H 2 O 2 generation is hindered on the surfaces of SnO 2 in the absence of HCO 3 species. In contrast, more H 2 O 2 is detected for SnO 2 films tested in HCO 3 − aqueous solution than those measured in non-bicarbonate electrolyte. Nevertheless, our kinetic simulations suggest that the co-adsorption of HCO 3 species adjacent to H 2 O on the (1 1 2) and (3 1 0) surfaces of SnO 2 do not effectively promote the two-electron WOR to form H 2 O 2 . Considering that the H 2 O 2 production scales linearly with the concentration of HCO 3 − , bicarbonate is likely to directly participate in the process of H 2 O 2 generation as a catalytic medium. That is, the mechanism that H 2 O 2 is formed through the hydrolyzation of HCO 4 − that is produced by the peroxidation of HCO 3 − is likely. Our calculations show that H 2 O 2 is formed through this route on both (1 1 2) and (3 1 0) facets of SnO 2 . In addition, the (1 1 2) surface of SnO 2 is kinetically favored for H 2 O 2 generation compared to the (3 1 0) facet.