Operando Transmission Electron Microscopy Insights Into the Evolution of Cu₂O-SnO₂-Based Catalysts During CO₂RR

The electrochemical reduction of CO₂ into valuable products is a promising strategy for mitigating atmospheric CO₂ emissions, particularly coupled with solar energy. Among the possible products, CO is currently most attractive, both because it can combine with hydrogen to produce syngas, and because CO is a key reactant in the chemical industry. Copper-based electrocatalysts are extensively investigated for CO₂ reduction; however, their morphological and chemical evolution under operating conditions still needs to be clarified, to understand the relationship between morphology, structure, and catalytic activity. This paper discusses a Cu₂O-SnO₂ based-catalyst, designed to enhance CO selectivity, and studies its evolution under reaction conditions by operando electrochemical liquid-phase transmission electron microscopy (EC-LPTEM). First, the morphology and composition of the as-prepared catalyst is characterized. Then, operando EC-LPTEM is discussed and compared to the post mortem catalyst characterization, together with electrochemical behavior evaluated in the lab-scale device. Different experimental conditions were studied to provide insights on how the catalyst modifies during the electrochemical activity. This characterization contributes to a better understanding of the possible mechanisms involved in the CO₂ reduction, and of the factors influencing the catalyst stability and selectivity, supporting the development of improved catalysts for CO₂ to syngas conversion.