Synergies between electrochemical oxidation and activated carbon adsorption in three-dimensional boron-doped diamond anode system

In order to enhance the performance of boron-doped diamond (BDD) anode system, activated carbon is added into BDD anode system to construct a three-dimensional electrode system. The degradation rates of p-nitrophenol and COD were significantly improved by 2–7 times compared to two-dimensional BDD anode system. More importantly, the synergy between electrochemical oxidation and activated carbon adsorption was observed. Investigations revealed that the synergy was not only resulted from direct electrochemical oxidation at activated carbon, but also from electro-catalysis of activated carbon to indirect electrochemical oxidation mediated by hydroxyl radicals. Although oxygen was reduced to hydrogen peroxide at the activated carbon surface, but the oxidation of hydrogen peroxide was not the main reason for the improvement of three-dimensional electrode system due to its relative weak oxidation capacity. Instead, the decomposition of hydrogen peroxide to hydroxyl radicals at catalysis of activated carbon played an important role on the enhancement of three-dimensional electrode system.