CO2 reduction on gas-diffusion electrodes and why catalytic performance must be assessed at commercially-relevant conditions

Thomas Burdyny,Wilson A Smith

doi:10.1039/c8ee03134g

Abstract

The substantial implications of high current densities on the local reaction environment and design of catalysts for electrochemical CO2 reduction are addressed. The presented perspectives also reflect on current practices within the field and offer new opportunities for both future catalyst and system-focused research efforts.

Highlights

Electrocatalytic CO2 reduction has the dual-promise of neutralizing carbon emissions in the near future, while providing a long-term pathway to create energy-dense chemicals and fuels from atmospheric CO2
Few of these catalysts have been tested at commercially-relevant current densities (B200 mA cmÀ2) due to transport limitations in traditional testing configurations and a research focus on fundamental catalyst kinetics, which are measured at substantially lower current densities
We consider that the unavoidable interactions between an acidic reagent and commonly-used electrolytes may result in inherently unstable CO2 reduction systems, suggesting that greater research focus is needed in system design to avoid this outcome

Summary

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Catalyst innovations have played a pivotal role in these advances, with a steady stream of new catalysts providing gains in CO2 conversion efficiencies and selectivities of both C1 and C2 products Few of these catalysts have been tested at commercially-relevant current densities (B200 mA cmÀ2) due to transport limitations in traditional testing configurations and a research focus on fundamental catalyst kinetics, which are measured at substantially lower current densities. As a consequence of this, the surface properties of many CO2 reduction catalysts risk being optimized for the wrong operating conditions The goal of this perspective is to communicate the substantial impact of reaction rate on catalytic behaviour and the operation of gas-diffusion layers for the CO2 reduction reaction. This work motivates high current density catalyst testing as a necessary step to properly evaluate materials for electrochemical CO2 reduction, and to accelerate the technology toward its envisioned application of neutralizing CO2 emissions on a global scale

Broader context

Professor in the Department of Chemical Engineering at Delft

Impact of high current densities on system design

Findings

Conclusion