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Insights into the carbon balance for CO2 electroreduction on Cu using gas diffusion electrode reactor designs

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Abstract

In this work, the carbon balance during high-rate CO2 reduction in flow electrolyzers was rigorously analyzed. The CO2 consumption at gas-diffusion electrodes due to electrochemical conversion and reaction with OH at the electrode/electrolyte interface leads to a substantial reduction in the volumetric flowrate of gas flow out of the electrolyzer, especially when highly concentrated alkaline electrolytes and elevated current densities are utilized, which is primarily due to an elevated pH at cathode/electrolyte interface. Without considering the CO2 consumption, the faradaic efficiencies for major gas products could be significantly overestimated during high current density CO2 reduction conditions, particularly in the case of high pH electrolyte. In addition, a detailed carbon balance path is elucidated via a two-step procedure of CO2 reaction with OH at the cathode/electrolyte interface and subsequent CO2 generation at the anode/electrolyte interface caused by a relatively low pH in the vicinity of the anode. Based on the proposed two-step carbon balance path, a systematic exploration of gases released in the anolyte reveals the transformation of a HCO3 or OH catholyte to a CO32− catholyte, which was further confirmed by pH measurements.

Graphical abstract: Insights into the carbon balance for CO2 electroreduction on Cu using gas diffusion electrode reactor designs

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Article information


Submitted
06 Jan 2020
Accepted
12 Feb 2020
First published
12 Feb 2020

Energy Environ. Sci., 2020, Advance Article
Article type
Paper

Insights into the carbon balance for CO2 electroreduction on Cu using gas diffusion electrode reactor designs

M. Ma, E. L. Clark, K. T. Therkildsen, S. Dalsgaard, I. Chorkendorff and B. Seger, Energy Environ. Sci., 2020, Advance Article , DOI: 10.1039/D0EE00047G

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