Study on Influence Factors of H₂O₂ Generation Efficiency on Both Cathode and Anode in a Diaphragm-Free Bath

Electrosynthesis of H₂O₂ via both pathways of anodic two-electron water oxidation reaction (2e-WOR) and cathodic two-electron oxygen reduction reaction (2e-ORR) in a diaphragm-free bath can not only improve the generation rate and Faraday efficiency (FE), but also simplify the structure of the electrolysis bath and reduce the energy consumption. The factors that may affect the efficiency of H₂O₂ generation in coupled electrolytic systems have been systematically investigated. A piece of fluorine-doped tin oxide (FTO) electrode was used as the anode, and in this study, its catalytic performance for 2e-WOR in Na₂CO₃/NaHCO₃ and NaOH solutions was compared. Based on kinetic views, the generation rate of H₂O₂ via 2e-WOR, the self-decomposition, and the oxidative decomposition rate of the generated H₂O₂ during electrolysis in carbonate electrolytes were investigated. Furthermore, by choosing polyethylene oxide-modified carbon nanotubes (PEO-CNTs) as the catalyst for 2e-ORR and using its loaded electrode as the cathode, the coupled electrolytic systems for H₂O₂ generation were set up in a diaphragm bath and in a diaphragm-free bath. It was found that the generated H₂O₂ in the electrolyte diffuses and causes oxidative decomposition on the anode, which is the main influent factor on the accumulated concentration in H₂O₂ in a diaphragm-free bath.