Singlet oxygen generation for selective oxidation of emerging pollutants in a flow-by electrochemical system based on natural air diffusion cathode

Abstract The decay of free radicals involved in side reactions is one of the challenges faced by electrochemical degradation of organic pollutants. To this end, a non-radical oxidation process was constructed by a natural air diffusion cathode (ADC) and a RuO2-Ti anode for cathodic hydrogen peroxide activation by anodic chlorine evolution. The ADC fabricated by the carbon black of BP2000 produced a stable concentration of hydrogen peroxide of 339.94 mg/L (current efficiency of 73.4%) without aeration, which was superior to the cathode made by the carbon black of XC72. The flow-by electrochemical system consisted of an ADC and a RuO2-Ti anode showed high selectivity to aniline compared to benzoate. Quenching experiments revealed the main active intermediate responsible for the pollutant degradation was singlet oxygen (1O2), which was also identified by the electron spin resonance (ESR) analysis. Finally, the steady-stable content of 1O2 was quantitatively determined to be 6.25×10− 11 M by the method of furfuryl alcohol (FFA) probe. Our findings provide a fast, low energy consumption and well controlled electrochemical oxidation method for selective degradation of organic pollutants.