Unraveling the role of electrolytes during electrochemical oxidation by differential electrochemical mass spectrometry. (10th August 2021)

• Record Type: Journal Article
• Authors: Mostafa, Ehab; Baltruschat, Helmut; Garcia-Segura, Sergi
• Is Part Of: Electrochimica acta. Volume 387(2021)
• Publication Date: 2021-08-10
• Subjects: Electrochemical advanced oxidation processes (EAOPs) -- Boron-doped diamond anodes (BDD) -- Water treatment -- Chlorine volatile species -- Oxalic acid -- Persistent organic pollutants; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2021.138521
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Differential electrochemical mass spectrometry monitor incineration at BDD anode. CO oxidation occurs by electrogenerated OH radicals at the BDD anode. Oxalic acid oxidation occurs via OH radicals and other oxidants produced at BDD. High oxalic acid oxidation capability in perchlorate and chloride electrolytes. Abstract: A fundamental understanding of the role of supporting electrolytes on the electrochemical oxidation of organics is essential to develop strategies for water treatment applications. This work completes research efforts of literature by evaluating directly the evolution of CO2 at the BDD electrode as a result of the mineralization of oxalic acid. The use of differential electrochemical mass spectrometry (DEMS) as an electroanalytical tool enables online measurement of engineering figures of merit of electrochemical advanced oxidation technologies and unravels the influence of coexisting ionic species in solution. Furthermore, the oxidation of CO is conducted to elucidate how different electrogenerated oxidants may be involved in oxidation reactions. CO2 current efficiencies calculated for the oxidation of CO were higher for electrolytes where more OH radicals are available for the oxidation of CO which suggests the OH radicals-mediated CO oxidation at BDD. Thereby, higher efficiency was observed in the perchlorate electrolyte than nitrate, sulfate, and chloride electrolytes. The decrease in the CO2 current efficiencies in the other electrolytes is explained by the competitive consumption of OH due to the formation of other oxidants such as SO4 –, Cl, other chlorine active species, and possibly also NO4 − . CO2 was the predominant oxidation product during the oxidation of oxalic acid in all electrolytes with a higher oxidation capability in the perchlorate and chloride electrolytes than nitrate and sulfate. These results show that the oxidation of oxalic acid is mediated by OH, direct charge transfer, as well as by other oxidants produced at the BDD at different electrolytes.