H2O2 production at gas-diffusion cathodes made from agarose-derived carbons with different textural properties for acebutolol degradation in chloride media

The excessive cost, unsustainability or complex production of new highly selective electrocatalysts for H2O2 production, especially noble-metal-based ones, is prohibitive in the water treatment sector. To solve this conundrum, biomass-derived carbons with adequate textural properties were synthesized via agarose double-step pyrolysis followed by steam activation. A longer steam treatment enhanced the graphitization and porosity, even surpassing commercial carbon black. Steam treatment for 20 min yielded the greatest surface area (1248 m2 g-1), enhanced the mesopore/micropore volume distribution and increased the activity (E1/2 = 0.609 V) and yield of H2O2 (40%) as determined by RRDE. The upgraded textural properties had very positive impact on the ability of the corresponding gas-diffusion electrodes (GDEs) to accumulate H2O2, reaching Faradaic current efficiencies of ~95% at 30 min. Acidic solutions of β-blocker acebutolol were treated by photoelectro-Fenton (PEF) process in synthetic media with and without chloride. In urban wastewater, total drug disappearance was reached at 60 min with almost 50% mineralization after 360 min at only 10 mA cm-2. Up to 14 degradation products were identified in the Cl−-containing medium. [Display omitted] •Gas-diffusion electrodes (GDEs) made from agarose-derived metal-free C electrocatalysts.•Enhanced textural properties upon steam treatment: greater surface area and mesoporosity.•Positive impact of improved textural properties: greater electroactivity and stability of GDEs.•H2O2 electrosynthesis: 60.5% efficiency at 360 min, greater than commercial GDE.•Total degradation of acebutolol by photoelectro-Fenton process, with 14 products identified.