Electrocatalytic activities of engineered carbonaceous cathodes for generation of hydrogen peroxide and oxidation of recalcitrant reactive dye

Abstract The electrocatalytic activity, H2O2 generation capacities and kinetics, and energy consumption of engineered carbonaceous cathodes including graphite plate, graphite felt, carbon felt, activated carbon felt and carbon fiber felt (CFF) was systematically evaluated in a double-chamber electrolysis system. The CFF cathode exhibited an excellent electrocatalytic activity in 2-electron oxygen reduction for H2O2 generation in both acidic and alkaline solutions. Furthermore, Reactive Red X-3B oxidation efficacy of carbonaceous cathodes via electro-generated H2O2 was compared in synthetic dyeing wastewater. The nature of carbonaceous materials dominated the degradation of Reactive Red X-3B in the cathodic chamber. Decolorization rate of more than 99% was achieved in all the cathodes tested, but there was a significant difference in the rate of mineralization. It was found that CFF was outclassed by 24.54% COD removal and high H2O2 generation ability in long runs. The degradation rate constant of Reactive Red X-3B in the CFF cathode chamber was 3.3 times faster than that of the graphite felt with rate constants of 1.27 × 10−3 min−1 and 3.82 × 10−4 min-1, respectively. The desirable stability and electrocatalytic activity of CFF were attributed to the better graphitic structure, higher conductivity and electroactive surface area with N-containing functional groups. Our findings demonstrate the potential of CFF to be used as a high-efficiency cathode in the electrochemical treatment of recalcitrant pollutants in practical applications.