Electrocatalyst Transformations Under Reaction Conditions—Insights from Operando Transmission Electron Microscopy of Well-Controlled Pre-Catalysts

The conversion of base molecules found in our environment (e.g., H₂O, CO₂) into the valuable chemicals and fuels needed by our modern society via electrocatalysis is currently an active area of research due to its potential for green energy applications. However, for many of these technologies, the search for optimal catalysts is still a laborious process because we lack a robust understanding of the relationship between a catalyst’s structure and its catalytic function. It is important to note that the catalytic performance is not solely determined by the starting catalyst (or pre-catalyst) structure, the dynamic catalyst structure that exists under reaction conditions also plays a key role. Moreover, probing this dynamic structure is not straightforward because it may not be retained when we examine the catalysts after reaction in the absence of the electrolyte and applied potential. Here, I will present work from my group studying the dynamical transformations that take place in Cu-based catalysts for the electrochemical reduction of carbon dioxide using <i>operando</i> electrochemical cell transmission electron microscopy (EC-TEM). To elucidate the impact of these transformations on catalytic performance, we adopted highly tuneable catalyst synthesis strategies that generate near-identical electrocatalysts for both EC-TEM and benchtop electrochemical and product selectivity measurement setups. Our <i>in situ</i> observations indicate that the application of a reductive potential generally leads to drastic structural changes, such as catalyst detachment, fragmentation, and re-deposition, within minutes. I will also discuss how these effects correlate with changes in catalyst activity and selectivity, thereby providing insights that can inform the design of better electrocatalysts.