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

• Process integration in H 2 O 2 production using BiVO 4 anode and carbonaceous GDC cathode. • Great improvement in production rates and efficiencies by irradiating blue light. • Electrolyte concentration improves cathodic production rate. • Negative effect of competing reactions on anodic efficiency. • -Greener and efficient performance using HCO 3 - electrolyte. This study examines the feasibility of greener and more efficient (photo)electrosynthesis of hydrogen peroxide (H 2 O 2 ) by coupling the anodic and cathodic processes within the same cell and evaluating bicarbonate (HCO 3 - ) as an alternative electrolyte to sulfate (SO 4 2- ). Results confirm the viability of paired H 2 O 2 production in (photo)electrolyzers equipped with a carbon-based gas diffusion cathode (GDC) and a BiVO 4 -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 HCO 3 - solutions enhanced H 2 O 2 production in electrocatalysis but was slightly less efficient than SO 4 ²⁻ in photoelectrocatalysis. The highest energy efficiency was achieved with SO 4 ²⁻ under blue light at 3.5 V, reaching 1.91 and 5.14 mmol H 2 O 2 Wh -1 in the anodic and cathodic compartments, respectively, for a total of 7.05 mmol H 2 O 2 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 HCO 3 - , the anodic and cathodic efficiencies were 0.84 and 3.79 mmol H 2 O 2 Wh -1 , respectively, resulting in a global efficiency of 4.63 mmol H 2 O 2 Wh -1 (0.30 μmol min -1 ). These findings highlight the potential of paired (photo)electrosynthesis for improving H 2 O 2 production while considering electrolyte sustainability.