Interplay of the electrolyte on CO2 reduction selectivity in copper gas-diffusion electrodes
Thomas Burdyny a
a Department of Chemical Engineering, Delft University of Technology (TU Delft), The Netherlands, Netherlands
Invited Speaker, Thomas Burdyny, presentation 035
Publication date: 7th June 2020

An ever-increasing number of works have assessed the activity of CO2 electrolysis on copper catalysts, specifically targeting high selectivities towards multi-carbon products such as ethylene and ethanol. From a catalytic perspective, many works have examined the impact that catalyst morphology and restructuring have on activity. The conditioning of the pre-catalyst, exposed facets and applied potential have continuously been shown to impact not only C2 product formation, but the stability of the catalyst.

 

As part of the 'catalyst', the environment around copper is similarly important. The role of electrolyte pH has been relentlessly assessed both experimentally and theoretically, and has shown to be a dominating factor in CO2 reduction; heavily due to hydrogen evolution maintaining a pH-dependent potential as compared to the pH-independent nature of CO2 to *CO. For these reasons the selectivity of CO2 reduction benefits at higher pH, and has shown large performance differences when using KHCO3, KCl and KOH electrolytes.

 

In this work we describe the impact of changes in the reaction environment at higher current densities for 3 different electrolytes. Specifically, we wanted to understand if the choice of electrolyte was important as it seems when production rate is pushed to the extreme using gas-diffusion electrodes. Through a combined modelling and experimental study we show that 1 M KHCO3, KCl and KOH show identical catalytic performance at 300 mA/cm2. Using experimental data as an input we find that [CO2], [CO], pH and the standard hydrogen potential are similar at higher current densities despite their apparent differences at lower current densities. Such findings help us to consolidate past findings within the field, and begin to better understand the interplay between catalysts, the electrolyte and proximity to a gas-liquid interface.

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