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Electrolyte Effects on the Faradaic Efficiency of CO₂ Reduction to CO on a Gold Electrode.

ABSTRACT: The electrochemical reduction of CO₂ aims to be a central technology to store excess electricity generated by wind and solar energy. However, the reaction is hindered by the competition with the hydrogen evolution reaction. In this paper, we present a detailed quantitative study of the Faradaic efficiency (FE) to CO on a gold electrode under well-defined mass-transport conditions using rotating ring-disk electrode voltammetry. Varying the concentration of the bicarbonate and the electrolyte cation employing different rotation rates, we map out how these parameters affect the FE(CO). We identify two different potential regimes for the electrolyte effects, characterized by a different dependence on the cation and bicarbonate concentrations. For hydrogen evolution, we analyze the nature of the proton donor for an increasingly negative potential, showing how it changes from carbonic acid to bicarbonate and to water. Our study gives detailed insights into the role of electrolyte composition and mass transport, and helps defining optimized electrolyte conditions for a high FE(CO).

SUBMITTER: Marcandalli G

PROVIDER: S-EPMC8154322 | biostudies-literature | 2021 May

REPOSITORIES: biostudies-literature

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Electrolyte Effects on the Faradaic Efficiency of CO<sub>2</sub> Reduction to CO on a Gold Electrode.

Marcandalli Giulia G Goyal Akansha A Koper Marc T M MTM

ACS catalysis 20210408 9

The electrochemical reduction of CO<sub>2</sub> aims to be a central technology to store excess electricity generated by wind and solar energy. However, the reaction is hindered by the competition with the hydrogen evolution reaction. In this paper, we present a detailed quantitative study of the Faradaic efficiency (FE) to CO on a gold electrode under well-defined mass-transport conditions using rotating ring-disk electrode voltammetry. Varying the concentration of the bicarbonate and the elect ...[more]

PMID: 34055454

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Project description:Understanding the electrolyte factors governing the electrochemical CO2 reduction reaction (CO2RR) is fundamental for selecting the optimized electrolyte conditions for practical applications. While noble metals are frequently studied, the electrolyte effects on the CO2RR on Sn catalysts are not well explored. Here, we studied the electrolyte effect on Sn metallic electrodes, investigating the impact of electrolyte concentration, cation identity, and anion properties, and how it shapes the CO2RR activity and selectivity. The activity for formic acid and carbon monoxide increases with the cation concentration and size at mild acid conditions. In contrast, hydrogen production is not strongly influenced by the cathodic potential, electrolyte concentration, and cation size. Furthermore, we have compared the CO2RR performance at a constant cation concentration in K2SO4 (pH 4) and KHCO3 (pH 7), where we show that the reaction rate toward HCOOH and CO are minimally impacted by the anion identity on the SHE scale, while being affected by the cations in solution, which we attribute to the reaction being limited by cation-coupled electron transfer steps rather than by a proton-coupled electron transfer step. We propose that the HCOOH forms via adsorbed hydrides leading to *OCHO intermediate, while CO forms through an electron transfer step, producing *CO2 δ-. Cations facilitate both processes by stabilizing the negatively charged intermediates, and the difference in the extent of the promotion of HCOOH over CO formation would stem from the stronger cation effects on *H compared with *CO2 δ- species. Additionally, the presence of HCO3 - at high concentrations (1.0 mol L-1) is shown to significantly enhance the production of H2 at high overpotentials (>-1.0 V vs RHE) due to bicarbonate ions acting as protons donors, outcompeting water reduction. These findings underscore the significance of electrolyte engineering for enhanced formic acid synthesis, offering valuable insights for optimizing the CO2RR processes on Sn electrocatalysts.

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Electrolyte Effects on the Faradaic Efficiency of CO₂ Reduction to CO on a Gold Electrode.

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Electrolyte Effects on the Faradaic Efficiency of CO<sub>2</sub> Reduction to CO on a Gold Electrode.

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Electrolyte Effects on the Faradaic Efficiency of CO2 Reduction to CO on a Gold Electrode.

Publications

Electrolyte Effects on the Faradaic Efficiency of CO<sub>2</sub> Reduction to CO on a Gold Electrode.

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OmicsDI is part of the ELIXIR infrastructure

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Electrolyte Effects on the Faradaic Efficiency of CO₂ Reduction to CO on a Gold Electrode.