Standard hydrogen electrode

Physics

Reversible hydrogen electrode

Electrode

Organic chemistry

Hydrogen

Analytical Chemistry (journal)

Faraday efficiency

Catalysis

Physical chemistry

Inorganic chemistry

Chemistry

Reference electrode

Mass transfer

Carbon monoxide

Proton

Quantum mechanics

Electrolyte

Chromatography

Electrochemistry

Journal of the American Chemical Society

In this article we investigate the electrochemical reduction of CO2 at gold electrodes under mildly acidic conditions. Differential electrochemical mass spectroscopy (DEMS) is used to quantify the amounts of formed hydrogen and carbon monoxide as well as the consumed amount of CO2. We investigate how the Faradaic efficiency of CO formation is affected by the CO2 partial pressure (0.1–0.5 bar) and the proton concentration (1–0.25 mM). Increasing the former enhances the rate of CO2 reduction and suppresses hydrogen evolution from proton reduction, leading to Faradaic efficiencies close to 100%. Hydrogen evolution is suppressed by CO2 reduction as all protons at the electrode surfaces are used to support the formation of water (CO2 + 2H+ + 2e– → CO + H2O). Under conditions of slow mass transport, this leaves no protons to support hydrogen evolution. On the basis of our results, we derive a general design principle for acid CO2 electrolyzers to suppress hydrogen evolution from proton reduction: the rate of CO/OH– formation must be high enough to match/compensate the mass transfer of protons to the electrode surface.

Suppression of Hydrogen Evolution in Acidic Electrolytes by Electrochemical CO<sub>2</sub> Reduction

Suppression of Hydrogen Evolution in Acidic Electrolytes by Electrochemical CO2 Reduction

Suppression of Hydrogen Evolution in Acidic Electrolytes by Electrochemical CO₂ Reduction