Visualizing the Surface Dynamics of Copper Electrodes under CO2 Reduction Conditions

Abstract

Electrochemical CO2 reduction reaction (eCO2RR) uses electricity, potentially sourced from sustainable and renewable energy, such as solar, wind and tidal energy, to convert CO2 into value-added chemicals and fuels. It is known that copper (Cu) is a remarkable catalyst material for eCO2RR because of its intrinsic nature to catalyze the formation of multi-carbon (C2+) products, such as ethylene and ethanol, which are valuable intermediates for chemicals and fuels manufacturing. However, the long-term stability of Cu-based electrodes is generally limited because they undergo dynamic structural and compositional changes during operation, which modifies the active sites and ultimately lead to catalyst degradation and a decline in their performance. Unfortunately, the mechanisms governing Cu restructuring and degradation remain incompletely understood. Atomic force microscopy (AFM) is a powerful analytical technique for obtaining high-resolution images of the three-dimensional Cu surface topography, where catalytic reactions occur. In this PhD Thesis, AFM was developed to achieve identical-grain measurements to reveal Cu facet-dependent surface restructuring during eCO2RR. In situ and operando AFM set-ups were developed to track the self-healing ability based on the dissolution-redeposition restructuring behavior of Cu electrode under realistic electrolyte conditions. Our findings highlight the critical importance of spatiotemporally resolved characterization, particularly for capturing reversible transformations that are often missed by ex situ measurements. These in situ and operando insights suggest that the community should shift its focus toward dynamic operational conditions and the rational design of dynamically evolving electrocatalyst materials with stable performance, rather than exclusively targeting structurally static catalyst materials.