Electrocatalytic arsenite oxidation in bicarbonate solutions combined with CO2 reduction to formate

Wonjung Choi, Minju Kim, Byeong ju Kim, Yiseul Park, Dong Suk Han, Michael R. Hoffmann, Hyunwoong Park

Research output: Contribution to journalArticle

Abstract

Sunlight-driven water-energy nexus technologies are receiving increasing attention. This study presents a hybrid electrochemical system that catalyzes the oxidation of As(III) to As(V) with a nanoparticulate TiO2 electrocatalyst (Ti/Ir1-xTaxOy/TiO2; denoted as an n-TEC) while simultaneously converting CO2 to formate on a Bi electrode in aqueous bicarbonate solutions at circum-neutral pH. Linear sweep voltammograms of n-TEC exhibit a specific As(III) oxidation peak (Ep,As), at which the Faradaic efficiency (FE) of As(V) production is ∼100 %. However, the application of a potential higher than the peak (E > Ep,As) leads to a significant decrease in the FE due to water oxidation. Upon the addition of chloride, the oxidation of water and chloride occur competitively, producing reactive chlorine species responsible for mediating the oxidation of As(III). The Bi electrodes synthesized via the electrodeposition of Bi3+ typically show high FEs of >80 % for formate production in bicarbonate solution purged with CO2. The addition of chloride significantly enhances the current while maintaining the FE. The n-TEC catalyst and Bi electrodes are paired in a single device equipped with a membrane, and significant effort is made to achieve the same FEs in both the anodic and cathodic reactions as in their half-reactions. Finally, the optimized n-TEC/Bi pair is coupled with a low-cost, commercially available photovoltaic (PV). Various technical factors that drive the overall reactions with the PV are considered, and maximum FEs of ∼95 % are achieved for the production of both As(V) and formate.

Original languageEnglish
Article number118607
JournalApplied Catalysis B: Environmental
Volume265
DOIs
Publication statusPublished - 15 May 2020

    Fingerprint

Keywords

  • Electrocatalysis
  • Redox reactions
  • Solar fuels
  • Water treatment
  • Water-energy nexus

ASJC Scopus subject areas

  • Catalysis
  • Environmental Science(all)
  • Process Chemistry and Technology

Cite this