Efficient Hydrogen Peroxide (H₂O₂) Synthesis by CaSnO₃ <i>via</i> Two-Electron Water Oxidation Reaction

Abstract

Electrochemical in situ hydrogen peroxide (H2O2) generation from a two-electron water oxidation reaction (2e-WOR) is a challenge, not only on catalyst selection but also on electrode making. Herein, the H2O2 electrocatalyst CaSnO3 nanoparticles were prepared by low-cost glucose as an agent and characterized by X-ray diffraction (XRD), thermogravimetric and differential scanning calorimetry (TG-DSC), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The active sites for the OH– adsorption on the surface CaSnO3 (121) was identified by density functional theory (DFT) calculation, and the corresponding reaction mechanism of H2O2 formation was proposed. The CaSnO3 nanoparticles can be formed from 650 to 850 °C, and the particle sizes are in the range of 27.2–37.3 nm. The mechanism of catalyst formation is that species of Ca and Sn reacted with oxygen to generate CaO and SnO2 during low-temperature calcination and CaSnO3 generated during high-temperature calcination. The active sites are the coordination-unsaturated Sn ions, which easily adsorb the negative-charge OH– from the solution, forming an OH* intermediate, and two adsorbed OH* can combine to generate a neutral H2O2 molecule. The H2O2 generation rate over CaSnO3 was calcinated at 850 °C is 347.7 μmol·min–1·g–1 at 2.6 V versus Ag/AgCl under dark conditions. The work opens an in situ H2O2 generation route, direct water oxidation, with wide application prospects.