Porous boron-doped diamond for efficient electrocatalytic elimination of azo dye Orange G

Abstract

Boron-doped diamond (BDD) is an ideal material being used for electrocatalytic elimination of environmental organic pollutants, but the commercial BDD electrodes have several limitations such as small electroactive area, slow mass transfer and low pollutants decomposition efficiency. In this paper, porous BDD electrodes with different pore sizes were synthesized by replicating porous Ti (powder metallurgy) with three-dimensional interoperable network structure, controllable aperture and porosity in a hot filament chemical vapor deposition (HFCVD) system. Various aspects of porous BDD with different pore sizes in terms of physicochemical properties, electrocatalytic reaction kinetics and mass transfer, which had not been previously researched, were systematically discussed. Meanwhile, some fundamental issues such as the enhancement mechanism of reaction kinetics of porous electrodes, the electrocatalytic degradation mechanism and pathways of contaminants on flat and porous BDD electrodes have been thoroughly investigated. Porous BDD electrodes had significantly higher Orange G (OG) electrocatalytic apparent reaction rate constants (up to 5.55 times that with flat BDD) and dramatically lower electrical energy per order (down to 25% that with flat BDD) for pollutant removal due to their increased electroactive area, reduced charge transfer resistance, and enhanced mass transfer. The electroanalysis, hydroxyl radical quenching and intermediates identification revealed the electrocatalytic degradation mechanism and reaction pathways of OG. In general, Porous BDD electrodes combined the properties of BDD and porous Ti, making them a commercially applicable and efficient material with high electroactive area, high electrocatalytic activity, long-term stability and low cost for electrocatalytic elimination of environmental organic pollutants.