Physics

Electrode

Nernst equation

Gas diffusion electrode

Diffusion

Analytical Chemistry (journal)

Physical chemistry

Overpotential

Inorganic chemistry

Chemistry

Supporting electrolyte

Cathode

Diffusion layer

Electrolyte

Chromatography

Electrochemistry

Thermodynamics

Journal of the American Chemical Society

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.

In Situ Observation of the pH Gradient near the Gas Diffusion Electrode of CO<sub>2</sub> Reduction in Alkaline Electrolyte

In Situ Observation of the pH Gradient near the Gas Diffusion Electrode of CO2 Reduction in Alkaline Electrolyte

In Situ Observation of the pH Gradient near the Gas Diffusion Electrode of CO₂ Reduction in Alkaline Electrolyte