In Situ Observation of the pH Gradient near the Gas Diffusion Electrode of CO2Reduction in Alkaline Electrolyte

Xu Lu, Chongqin Zhu, Zishan Wu, Jin Xuan, Joseph S. Francisco, Hailiang Wang

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

The local pH variation near the surface of CO2 reduction electrodes is important but hard to study. We develop a continuous-flow Raman electrochemical cell that enables the first experimental study of the local pH near a CO2 reduction gas diffusion electrode under reaction conditions. At zero current, CO2 chemically reacts with the 1 M KOH electrolyte at the interface to form HCO3- and CO32-. The local pH on the cathode surface is 7.2, and the HCO3- concentration profile extends a distance of 120 μm into the electrolyte, which verifies that the nominal overpotential reduction from using alkaline electrolyte originates from the Nernst potential of the pH gradient layer at the cathode/electrolyte interface. The CO2-OH- neutralization reaction and the pH gradient layer still persist, albeit to a reduced extent, at CO2 reduction current densities up to 150 mA/cm2.
Original languageEnglish (US)
Pages (from-to)15438-15444
Number of pages7
JournalJournal of the American Chemical Society
Volume142
Issue number36
DOIs
StatePublished - Sep 9 2020
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Colloid and Surface Chemistry
  • Chemistry(all)
  • Catalysis

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