Intensifying paired hydrogen peroxide (H2O2) electrosynthesis: Influence of electrolyte composition and light irradiation

Abstract

This study examines the feasibility of greener and more efficient (photo)electrosynthesis of hydrogen peroxide (H₂O₂) by coupling the anodic and cathodic processes within the same cell and evaluating bicarbonate (HCO₃^-) as an alternative electrolyte to sulfate (SO₄^2-). Results confirm the viability of paired H₂O₂ production in (photo)electrolyzers equipped with a carbon-based gas diffusion cathode (GDC) and a BiVO₄-coated FTO anode. Under constant cell potential, higher electrolyte concentrations led to increased current, enhancing H₂O₂ production in the cathodic process but not in the anodic one, suggesting the occurrence of competing anodic reactions. Coulombic and energy efficiencies decreased with electrolyte concentration but improved under light irradiation, with blue light yielding the highest efficiency. The use of HCO₃^- solutions enhanced H₂O₂ production in electrocatalysis but was slightly less efficient than SO₄²⁻ in photoelectrocatalysis. The highest energy efficiency was achieved with SO₄²⁻ under blue light at 3.5 V, reaching 1.91 and 5.14 mmol H₂O₂ Wh^-1 in the anodic and cathodic compartments, respectively, for a total of 7.05 mmol H₂O₂ Wh^-1 (production rate of 0.45 μmol min^-1 and 0.34 mmol l^-1 and faradaic efficiency of 132.4 %). In contrast, with HCO₃^-, the anodic and cathodic efficiencies were 0.84 and 3.79 mmol H₂O₂ Wh^-1, respectively, resulting in a global efficiency of 4.63 mmol H₂O₂ Wh^-1 (0.30 μmol min^-1). These findings highlight the potential of paired (photo)electrosynthesis for improving H₂O₂ production while considering electrolyte sustainability.