Selectivity

Physics

Electrode

Organic chemistry

Nernst equation

Diffusion

Analytical Chemistry (journal)

Catalysis

Physical chemistry

Overpotential

Inorganic chemistry

Chemistry

Cathode

Quantum mechanics

Chromatography

Electrochemistry

Electric field

Thermodynamics

ACS Catalysis

Conducting electrochemical reduction of CO2 in acidic media can effectively increase the utilization efficiency of CO2. Alkali cations (M+) are indispensable for CO2 reduction in acidic media, while the high concentration of M+ results in bicarbonate precipitation in a gas diffusion electrode. To develop selective and sustainable CO2 reduction techniques in acidic media, quantitative understandings of cation effects on reduction rates of CO2 and H+ are demanded. Previous study shows that M+ in acidic media can modulate the electric field distribution in a double layer, which suppresses H+ migration and stabilizes the intermediate of CO2 reduction. In this work, we conducted a more quantitative study through the combination of electrochemical experiments and generalized modified Poisson–Nernst–Planck (GMPNP) simulations. When the concentration of M+ is higher than that of H+, the migration of H+ is substantially suppressed. The diffusion rate of H+ is also influenced by the concentration of M+. Furthermore, the concentration and identity of M+ affect the electric field within the Stern layer, which is the driving force of the electron transfer from the cathode to CO2. Only in M+-containing solutions, the electric field strength within the Stern layer increases as the potential moves negatively, and CO2 reduction can be accelerated by applying a larger overpotential. These aspects together determine the selectivity of CO2 reduction in acidic solution.

Quantitative Understanding of Cation Effects on the Electrochemical Reduction of CO<sub>2</sub> and H<sup>+</sup> in Acidic Solution

Quantitative Understanding of Cation Effects on the Electrochemical Reduction of CO2 and H+ in Acidic Solution

Quantitative Understanding of Cation Effects on the Electrochemical Reduction of CO₂ and H⁺ in Acidic Solution