Photoelectrochemical Synthesis of Hydrogen Peroxide from Saline Water via the Two-Electron Water Oxidation Reaction.

Hydrogen peroxide (HO) production on the anode is more valuable than oxygen and chlorine evolution for photoelectrochemical saline water splitting. In this work, by the introduction of bicarbonate (HCO), HO is produced from saline water (2 M KHCO + 0.5 M NaCl aqueous solution) via the two-electron water oxidation reaction by a photoanode of bismuth vanadate (BiVO). Furthermore, the Faradaic efficiency (FE) and accumulation for HO are improved by coating antimony tetroxide (SbO) on BiVO. A HO FE of 26% at 1.54 V vs RHE is obtained by SbO/BiVO and 49 ppm of HO is accumulated after a 135 min chronoamperometry. Similar to that in KHCO pure water solution, infrared spectroscopy and electrochemical analysis confirm that HCO plays a surface-mediating role in the formation of HO in KHCO saline water solution. The presence of HCO in the electrolyte is able to not only increase the photocurrent density but also effectively inhibit the chlorine evolution reaction.