Influence of doping level on the electrochemical oxidation of formic acid on boron doped diamond electrodes

The influence of the boron doping level in boron doped diamond electrodes (BDD) on the electro-generation of active intermediates (hydroxyl radicals and hydrogen peroxide) involved in the oxidation of organic compounds has been studied. It is shown that the boron doping level of diamond electrodes has no influence on the amount of hydroxyl radicals produced at the electrode surface in contrast with hydrogen peroxide, whose formation is favored by low boron doping levels. The influence of the boron doping level on the degradation of formic acid is also investigated. It is shown that lowly doped diamond films have a slight advantage; proving that hydrogen peroxide does not participate in the process. Moreover, the experimental results were compared with a theoretical model, which considers that the oxidation reaction is fast and controlled by mass transfer. All BDD electrodes showed a good agreement with the model independently of the boron doping level. However, the accuracy of the model tend to decrease with increasing boron content, which is probably due to the participation of active couples, which are known to be present at the surface of diamond films with high boron doping levels.