Stability and Degradation Mechanisms of Copper‐Based Catalysts for Electrochemical CO₂ Reduction

Abstract

To date, copper is the only monometallic catalyst that can electrochemically reduce CO2 into high value and energy‐dense products, such as hydrocarbons and alcohols. In recent years, great efforts have been directed towards understanding how its nanoscale structure affects activity and selectivity for the electrochemical CO2 reduction reaction (CO2RR). Furthermore, many attempts have been made to improve these two properties. Nevertheless, to advance towards applied systems, the stability of the catalysts during electrolysis is of great significance. This aspect, however, remains less investigated and discussed across the CO2RR literature. In this Minireview, the recent progress on understanding the stability of copper‐based catalysts is summarized, along with the very few proposed degradation mechanisms. Finally, our perspective on the topic is given.

Potential‐Dependent Morphology of Copper Catalysts During CO2 Electroreduction Revealed by In Situ Atomic Force Microscopy

“…[9] Disentangling structural and catalytic properties proves to be intricate due to the dynamic nature of copper electrocatalysts with their structure,m orphology,c omposition, and oxidation state becoming altered during CO 2 RR. [10] Previous works showed the dynamic evolution of Cu nanoparticles [11] and electrode restructuring induced by electrochemical potentials [12] or surface-adsorbed species. [13] Studies on Cu model surfaces bear the potential of unravelling structureproperty relations and the mechanisms behind the observed facet-dependent product selectivity.…”

Towards a Critical Evaluation of Electrocatalyst Stability for CO2 Electroreduction

“…[13] Specifically for copper electrocatalysts, which are known to form multi-carbon products, electrocatalyst degradation can also be associated to the loss of well-defined facets and a decrease in particle size. [14] It is evident that for a thorough stability assessment, one needs a sufficient amount of data points to capture the trend of I p (t) or FE t ð Þ realistically. Additionally, for the comparison of selectivity or stability of different electrocatalysts, it is imperative that experimental parameters such as duration and sampling frequency are exactly the same for each experiment, since the sampling frequency may also introduce deviations in FE t ð Þ as shown in section 4 of the SI.…”

“…[10,11] Catalyst lifetimes are currently in the order of hours or a few days, while looking at similar mature electrocatalytic technologies (fuel cells, chlor-alkali and hydro-gen electrolyzers), catalyst lifetimes should be extended to years. [12] There is no unambiguous definition reported for electrocatalyst stability to date, [13,14] leading to poor and biased comparisons between electrocatalysts. A descriptor for stability generally accepted in the literature is the operational time for which a certain value of the faradaic efficiency (FE) or cell voltage remains approximately constant.…”

Pocket the difference

“…In the future, it would be important to understand why Cu nanoparticles undergo surface restructuring in the NOLI structure during the CO 2 reduction process. Judging from the specific conditions under which the NOLI structure is formed and CO 2 is reduced, one may conclude that this stability issue originates from the negative potential applied, which fragments nanoparticles 7 . An important study would be to investigate what factors can be used to stabilize Cu nanoparticles under negative potentials so that the advanced features of the NOLI structure can be applied to maximize the CO 2 conversion efficiency.…”