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Potentiometric Rotating Ring Disk Electrode Study of Interfacial pH during CO2 Reduction and H-2 Generation in Neutral and Weakly Acidic Media

Journal Contribution - Journal Article

Electrocatalytic reduction of CO2 to CO in aqueous media offers an important path to more sustainable carbon utilization. Optimization of this process relies on a detailed understanding of the dynamics of boundary layer chemistry, e.g., pH, adjacent to the electrode, which is difficult to quantify without perturbing the system. In this work, a versatile IrOx pH-sensing thin film is fabricated on the ring of a rotating ring disk electrode (RRDE) to enable potentiometric boundary layer pH measurement under well-defined mass flow conditions. An analytical reaction-convection-diffusion model is used to translate ring measurements to the pH at the disk surface under reaction conditions. The measurements and model effectively capture the drastic pH shear on a Au electrode during hydrogen evolution reaction in a weak acid electrolyte. The pH trends are measured during CO2 reduction reaction in a 0.5 mol L-1 bicarbonate electrolyte, where the impact of buffering action is clearly demonstrated as a function of the rotation rate and RRDE geometry. The model and measurement provide a useful platform for further exploration of electrode kinetics influenced by reaction-induced pH change.
Journal: Journal of Physical Chemistry C
ISSN: 1932-7447
Issue: 17
Volume: 126
Pages: 7456 - 7467
Publication year:2022
Accessibility:Closed