Competition between CO2 Reduction and Hydrogen Evolution on a Gold Electrode under Well-Defined Mass Transport Conditions

Journal of the American Chemical Society, vol. 142, pp. 4154–4161

Abstract

(CO2RR) to CO. However, the concomitant hydrogen evolution reaction (HER) remains unavoidable under aqueous conditions. In this work, a rotating ring disk electrode (RRDE) setup has been developed to study quantitatively the role of mass transport in the competition between these two reactions on the Au surface in 0.1 M bicarbonate electrolyte. Interestingly, while the faradaic selectivity for CO formation was found to increase with enhanced mass transport (from 67% to 83%), this effect is not due to an enhancement of the CO2RR rate. Remarkably, the inhibition of the competing HER from water reduction with increasing disk rotation rate is responsible for the enhanced CO2RR selectivity. This can be explained by the observation that, on the Au electrode, water reduction improves with more alkaline pH. As a result, the decrease in the local alkalinity near the electrode surface with enhanced mass transport suppresses HER due to the water reduction. Our study shows that controlling the local pH by mass transport conditions can tune the HER rate, in turn regulating the CO2RR and HER competition in the general operating potential window for CO2RR (-0.4 to -1 V vs RHE).

Authors 4

1. Akansha Goyal Aachen

   Leiden University

   Affiliation as printed

   Leiden University , , PO Box 9502, ,

   Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands

2. Giulia Marcandalli Aachen

   Leiden University

   Affiliation as printed

   Leiden University , , PO Box 9502, ,

   Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands

3. Vladislav A. Mints Aachen

   Leiden University

   Affiliation as printed

   Leiden University , , PO Box 9502, ,

   Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands

4. Marc T. M. Koper corresponding Aachen

   Leiden University

   Affiliation as printed

   Leiden University , , PO Box 9502, ,

   Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands