In the electrochemical CO2 reduction reaction (CO2RR) selectivity still remains an important issue. In this talk, I will showcase a few examples which highlight how shape-controlled nanocrystals can contribute to address this challenge. First of all, I will discuss how size control of Cu nanocubes (Cucub) and Cu octahedra (Cuoh) has revealed the importance of facet-ratio to maximize the selectivity towards ethylene and methane, respectively. Second, I will present our recent computational-experimental efforts towards using well-defined NCs to elucidate selectivity rules at the hydrocarbons/alcohols branching nodes in the CO2RR pathway. The formation of ethanol via *CHx-*CO coupling or *CO-*CO coupling is an open debate in the literature. As a platform to address this question, we have used CH4 favoring (i.e. *CHx populated) Cuoh and C2H4 favoring (i.e. *CO-*CO populated) Cucub under enhanced *CO coverage induced by the presence of Ag NCs. The selective promotion of ethanol on the Cuoh provided evidence for *CHx-*CO coupling being the preferred pathway. Following theoretical predictions, we have also demonstrated that such pathway is favored on Cu(110) edge sites compared to Cu(100) terraces by studying the size-dependent edge/face ratio of the Cucub always in the presence of the CO-generating Ag domains. Indeed, we found that smaller cubes are more selective for ethanol than bigger sizes. Generally, these examples encourage the application of well-defined nano catalysts as a bridge between theory and experiments in electrocatalysis.

Shape-controlled Cu nanocrystals to unlock selectivity pathways in the electrochemical CO2 reduction reaction

ACS Spring 2022

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