Unravelling the surface structure and active site of CaSnO3, as well as H2O2 formation mechanism in two electron water oxidation reaction

The two-electron water oxidation reaction (2e-WOR) is an eco-friendly process to produce H2O2, which attracts much attention due to its low cost and high safety. CaSnO3 is a potential industrial catalyst for 2e-WOR reaction with high performance. However, the surface structure and active site of CaSnO3, as well as H2O2 formation mechanism, are still unknown due to its complex structure and limitation of characterization technique in resolution of surface fine structure and intermediates. To solve this difficult problem, the authors systematically investigated the surface structures of CaSnO3 and the adsorption and reaction behaviors of H2O, OH and H2O2 on CaSnO3 by density functional theory method. The present work indicated that the O4(Sn) surface with 5-coordinated Sn is the most stable termination of CaSnO3(1 2 1) by comparing the surface energies of 17 terminations of CaSnO3(1 2 1); OH strongly chemisorbs at the top site of Sn on CaSnO3(1 2 1) and can diffuse on surface with the free energy barrier of 0.68 ∼ 1.07 eV; the coordination unsaturated Sn atom is the active site for OH adsorption and H2O2 formation. According to the deep understanding of the mechanism of the 2e-WOR reaction to H2O2 on CaSnO3, two practical ways were proposed to design and develop 2e-WOR catalysts with high performance.