On the activation and physical degradation of boron-doped diamond surfaces brought on by cathodic pretreatments

The electrochemical activation and physical degradation of boron-doped diamond (BDD) electrodes with different boron doping levels after repeated cathodic pretreatments are reported. Galvanostatic cathodic pretreatment passing up to −14000 C cm⁻² in steps of −600 C cm⁻² using −1 A cm⁻² caused significant physical degradation of the BDD surface, with film detachment in some areas. Because of this degradation, a great increase in the electrochemically active area was observed in Tafel plots for the hydrogen evolution reaction (HER) in acid media. The minimum cathodic pretreatment needed for the electrochemical activation of the BDD electrodes without producing any observable physical degradation on the BDD surfaces was determined using electrochemical impedance spectroscopy (EIS) measurements and cyclic voltammetry: −9 C cm⁻², passed at −1 A cm⁻². This optimized cathodic pretreatment can be safely used when electrochemical experiments are carried out on BDD electrodes with doping levels in the range between 800 and 8000 ppm.