Synthesis, characterisation and application of an exfoliated graphite–diamond composite electrode in the electrochemical degradation of trichloroethylene

Abstract

A composite electrode made up of exfoliated graphite (EG) and diamond was prepared for the electrochemical oxidation of trichloroethylene (TCE). The SEM images of the EG–diamond material showed that diamond powders were dispersed on the surface of EG materials. The N₂ adsorption–desorption isotherm of EG–diamond material resulted in a poor adsorption capability due to the insertion of diamond powders into the porous matrix of EG. Raman spectroscopy revealed the presence of characteristic sp³ bands of diamond confirming good interaction of diamond with EG. Electrochemical characterisation of EG–diamond in 0.1 M Na₂SO₄ resulted in an enhanced working potential window. The EG–diamond electrode was employed for the electrochemical oxidation of trichloroethylene (0.2 mM) in a Na₂SO₄ supporting electrolyte. The EG–diamond, in comparison to the pristine EG electrode, exhibited a higher removal efficiency of 94% (EG was 57%) and faster degradation kinetics of 25.3 × 10⁻³ min⁻¹ showing pseudo first order kinetic behaviour. Under the optimised conditions, 73% total organic content (TOC) removal was achieved after 4 h of electrolysis. The degradation of TCE was also monitored with gas chromatography-mass spectrometry. Dichloroacetic acid (DCAA) was identified as a major intermediate product during the electrochemical oxidation of TCE. The electrochemical degradation of TCE at the EG–diamond electrode represents a cost effective method due to the ease of preparation of EG–diamond composite material without the necessity of diamond activation which is normally achieved through doping.