Abstract
Boron doped diamond films (BDD) are the most studied electrocatalytic materials and their efficiency for removing organic compounds is attributed to their ability to produce a large amount of hydroxyl radicals by the electrolysis of water. However, some organic compounds are easy to degrade than others, as well as they also interact with BDD surface. Thus, it is necessary to understand the chemical/electrochemical process at the molecular level. In this frame, this work aims to study the electrochemical oxidation (EO) of oxalic acid (OA) at BDD anode, understanding the reaction mechanism, formation of hydroxyl radicals, the effect of supporting electrolyte concentration, and the role of oxidants in solution taking into consideration the cyclic and linear voltammetric measurements. Voltammetric results clearly reveal that a direct electron transfer is achieved as the main mechanistic behavior suffered by OA on BDD surface before oxygen reaction. However, the concentration of sulfates in solution plays an important role in the solvation, diffusion and adsorption species at BDD surface, promoting parallel mechanisms. From the information provided by experimental measurements, the preferential mechanism on BDD surface at low or high overpotential regions was elucidated.
Highlights
The electrochemical oxidation (EO) of organic compounds is an area of intense research in the field of environmental electrochemistry.[1]
Prior to understand the persulfate reactions and on the basis of the introductory considerations regarding the electrocatalytic nature of Boron doped diamond films (BDD) anode, electrochemical measurements were performed to increase the understanding of mechanisms related to the supporting electrolyte oxidation as well as the model organic compound oxidation by involving the participation of oxygen reactive species, like hydroxyl radicals
The signal is dependent on the supporting electrolyte concentration, considering that its concentration is different in both cases (0.0001 and 0.00001 M), because the solvation effect plays an important role on the interaction of oxalic acid (OA) molecules and BDD surface.[9,10,11]
Summary
The electrochemical oxidation (EO) of organic compounds is an area of intense research in the field of environmental electrochemistry.[1] This process can occur by two main mechanisms: direct oxidation at the electrode surface or indirect oxidation mediated by strong oxidants generated at the electrode surface. In the former, pollutants are destroyed directly at anode’s surface (M) by direct electron transfer, yielding very poor decontamination. In the case of persulfate,[2] its production is not feasible at all electrodes because it mainly depends on the nature of electrocatalytic material used It can be produced by direct oxidation of the sulfate ions (equation 1) or by indirect oxidation via OH (equations 2 and 3)
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