Mechanism of Cations Suppressing Proton Diffusion Kinetics for Electrocatalysis

Abstract

Proton transfer is crucial for electrocatalysis. Accumulating cations at electrochemical interfaces can alter the proton transfer rate and then tune electrocatalytic performance. However, the mechanism for regulating proton transfer remains ambiguous. Here, we quantify the cation effect on proton diffusion in solution by hydrogen evolution on microelectrodes, revealing the rate can be suppressed by more than 10 times. Different from the prevalent opinions that proton transport is slowed down by modified electric field, we found water structure imposes a more evident effect on kinetics. FTIR test and path integral molecular dynamics simulation indicate that proton prefers to wander within the hydration shell of cations rather than to hop rapidly along water wires. Low connectivity of water networks disrupted by cations corrupts the fast‐moving path in bulk water. This study highlights the promising way for regulating proton kinetics via a modified water structure.

Electrochemical Hydrogenation of Aliphatic Aldehydes and Acids using Pentlandite Catalysts

“…This increase in FE is presumably achieved by the transport of potassium ions to the catalyst or the lower hydrophobicity of the electrode surface. While the latter could improve the aldehyde adsorption in catalyst layer, the presence of cations is known to suppress proton reduction [54,55].…”

Interaction of Cathode Interface Microenvironment and Anode Electrolyte in Zero-Gap Electrolyzer for CO2 Conversion

“…This is attributed to the aggregation of cations in the outer Helmholtz plane, which hinders proton migration and hydrogen evolution reaction. 13,14 Additionally, the accumulation of cations enhances the local electric field intensity, promoting CO 2 adsorption and C−C coupling. 15,16 Furthermore, cations also exert a certain influence on the cathode catalyst.…”

“…Moreover, the alkaline metal cations present in the electrolyte have been proven to play a beneficial role in the electroreduction of carbon dioxide. This is attributed to the aggregation of cations in the outer Helmholtz plane, which hinders proton migration and hydrogen evolution reaction. , Additionally, the accumulation of cations enhances the local electric field intensity, promoting CO 2 adsorption and C–C coupling. , Furthermore, cations also exert a certain influence on the cathode catalyst. A study has indicated that the percentage of Cu in the surface oxidation state decreases with the increase of cation crossing: at high anode electrolyte concentration, only Cu 0 is present, whereas at low anode electrolyte concentration, both Cu 0 and Cu + coexist .…”