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

Hydrogen peroxide (H 2 O 2 ) 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 3 - ), H 2 O 2 is produced from saline water (2 M KHCO 3 + 0.5 M NaCl aqueous solution) via the two-electron water oxidation reaction by a photoanode of bismuth vanadate (BiVO 4 ). Furthermore, the Faradaic efficiency (FE) and accumulation for H 2 O 2 are improved by coating antimony tetroxide (Sb 2 O 4 ) on BiVO 4 . A H 2 O 2 FE of 26% at 1.54 V vs RHE is obtained by Sb 2 O 4 /BiVO 4 and 49 ppm of H 2 O 2 is accumulated after a 135 min chronoamperometry. Similar to that in KHCO 3 pure water solution, infrared spectroscopy and electrochemical analysis confirm that HCO 3 - plays a surface-mediating role in the formation of H 2 O 2 in KHCO 3 saline water solution. The presence of HCO 3 - in the electrolyte is able to not only increase the photocurrent density but also effectively inhibit the chlorine evolution reaction.