Photoelectrochemical\nSynthesis of Hydrogen Peroxide\nfrom Saline Water via the Two-Electron Water Oxidation Reaction

Hydrogen\nperoxide (H<sub>2</sub>O<sub>2</sub>) production on the\nanode is more valuable than oxygen and chlorine evolution for photoelectrochemical\nsaline water splitting. In this work, by the introduction of bicarbonate\n(HCO<sub>3</sub><sup>–</sup>), H<sub>2</sub>O<sub>2</sub> is\nproduced from saline water (2 M KHCO<sub>3</sub> + 0.5 M NaCl aqueous\nsolution) via the two-electron water oxidation reaction by a photoanode\nof bismuth vanadate (BiVO<sub>4</sub>). Furthermore, the Faradaic\nefficiency (FE) and accumulation for H<sub>2</sub>O<sub>2</sub> are\nimproved by coating antimony tetroxide (Sb<sub>2</sub>O<sub>4</sub>) on BiVO<sub>4</sub>. A H<sub>2</sub>O<sub>2</sub> FE of 26% at\n1.54 V vs RHE is obtained by Sb<sub>2</sub>O<sub>4</sub>/BiVO<sub>4</sub> and 49 ppm of H<sub>2</sub>O<sub>2</sub> is accumulated after\na 135 min chronoamperometry. Similar to that in KHCO<sub>3</sub> pure\nwater solution, infrared spectroscopy and electrochemical analysis\nconfirm that HCO<sub>3</sub><sup>–</sup> plays a surface-mediating\nrole in the formation of H<sub>2</sub>O<sub>2</sub> in KHCO<sub>3</sub> saline water solution. The presence of HCO<sub>3</sub><sup>–</sup> in the electrolyte is able to not only increase the photocurrent\ndensity but also effectively inhibit the chlorine evolution reaction.