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

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 Na ₂SO₄ 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.