Activated carbon filled in a microporous titanium-foam air diffusion electrode for boosting H₂O₂ accumulation

In the electro-Fenton process, there still suffers concern of low H₂O₂ generation caused by inadequate mass transfer of oxygen and low selectivity of oxygen reduction reaction (ORR). To solve it, in this study, various particle sizes (850 μm, 150 μm, and 75 μm) of granular activated carbon filled in a microporous titanium-foam substate was used to develop a gas diffusion electrode (AC@Ti–F GDE). This facile-prepared cathode has seen a 176.15% improvement in H₂O₂ formation compared to the conventional one. Aside from a much higher oxygen mass transfer by creating gas-liquid-solid three-phase interfaces coupled with much high dissolved oxygen, the filled AC played a significant role in H₂O₂ accumulation. Among these particle sizes of AC, the one in 850 μm has observed the highest H₂O₂ accumulation, reaching 1487 μM in 2 h electrolysis. Because there is a balance between chemical nature for H₂O₂ formation and micropore-dominant porous structure for H₂O₂ decomposition, resulting in an electron transfer of 2.12 and H₂O₂ selectivity of 96.79% during ORR. In a word, the facial AC@Ti–F GDE configuration is promising for H₂O₂ accumulation.