Interplay of Local pH and Cation Hydrolysis during Electrochemical CO₂ Reduction Visualized by In Operando Chemical Shift-Resolved Magnetic Resonance Imaging

Abstract

The Cu-catalyzed electrochemical CO 2 reduction enables the conversion of greenhouse gas emissions to fuels or platform chemicals with prospects of storing intermittent energy from renewable sources. While current research in tuning catalyst activity and product selectivity is often mired in finding electrode engineering solutions, the importance of electrolyte engineering is mostly overlooked. This study presents a method for measuring local pH profiles in electrode proximity and correlating them to cation-induced buffering effects. Magnetic resonance imaging (MRI) techniques were applied to evaluate the local pH values using spatially resolved 13 C resonances of the CO 2 /HCO 3 − /CO 3 2− equilibrium. The buffering effect of cation hydrolysis is substantiated by local shifts of the 23 Na resonance of Na + in the NaHCO 3 electrolytes. Steeper local pH gradients, compared to experiments with KHCO 3 , account for increased selectivity for acetate formation from the solution-based reaction. Proven itself capable of elucidating the effect of cations on local pH values, our presented method supports tailoring the electrode−electrolyte interface to selectively generate value-added products.

Ag–Sb/Cu by Galvanic Replacement: Electrochemical CO2 Reduction and Unveiling C3+ Hydrocarbon Pathways

“…Minor acetate production involves *COH + *CO → CH 3 COO – . In addition to the electrode-specific mechanism, the involvement of electrolyte effects in electrochemical processes introduces a multitude of factors that significantly impact the overall system dynamics. − These effects encompassed parameters such as pH, buffering capability, CO 2 solubility, local CO 2 concentration, cation/anion ratio, CO 2 /HCO 3 – /CO 3 2– equilibrium, and cation size, adding complexity to the overall process. The implementation of density functional calculations would greatly contribute to our understanding of the mechanism.…”

Correction to “Interplay of Local pH and Cation Hydrolysis during Electrochemical CO2 Reduction Visualized by In Operando Chemical Shift-Resolved Magnetic Resonance Imaging”

“…The original version of the article with DOI 10.1021/acs.jpcc.3c03563 1 does not contain a data availability statement, which is supplied hereafter.…”