Thermally treated candle soot as a novel catalyst for hydrogen peroxide in-situ production enhancement in the bio-electro-Fenton system

Abstract Thermally treated candle soot (TCS) was used as a two-electron (2e¯) oxygen reduction reaction (ORR) catalyst to in situ produce H2O2 in a bio-electro-Fenton (BEF) system. Compared with the pristine candle soot (CS), TCS showed larger Brunauer-Emmett-Teller (BET) surface area (102.54 m2 g−1 vs. 61.79 m2 g−1), higher mesoporous ratio (50.39% vs. 34.98%), and improved hydrophilicity. X-ray photoelectron spectra (XPS) results revealed that the C–O–C was the dominant oxygen-containing group of the CS, and its percentage reached at 80.55%. However, the C–O–C ratio of the TCS decreased to 48.93%, whilst it’s C O and O C–O ratios significantly increased to 27.92% and 23.15%. The TCS showed a high H2O2 selectivity (87.5%∼97.0%) at the neutral pH condition, which was much higher than that of the commonly used carbon black (CB) catalyst. Finally, the H2O2 concentration maxima (Cmax-H2O2) of the bio-electro-Fenton system running with the TCS air-cathode (BEF-TCS) achieved at 32.02 mg/L, which was 6.29 times higher than that of the BEF-CB (5.09 mg/L). The removal and mineralization ratios of the SMX in the BEF-TCS reached at 83.0% and 79.0%, respectively. This paper reported a novel 2e¯ ORR electro-catalyst which was low-cost, easily available and highly efficiency.