Interplay of Particle Size and Facet Engineering in Cu Nanocatalysts for Enhanced CO₂ Reduction in Static System

This work demonstrates how particle size and facet orientation in copper nanocrystals influence CO₂ electroreduction efficiency in a static H-cell system. Three Cu nanocrystal morphologies are studied: blood flow (BF, {100} facets, larger size), spherical (SP, {111} facets, similar size as BF), and trigonal (TR, {100} facets, different size). Although BF and TR share the {100} orientation, they show contrasting selectivity BF favors ethylene (≈60% Faradaic efficiency at −90 mA cm⁻²), while TR promotes formate (85% FE at −39 mA cm⁻²), underscoring the effect of size. SP, with the same size as BF but {111} facets, produces CO (78% FE at −35 mA cm⁻²), highlighting the role of facet orientation. Operando Raman spectroscopy identifies key intermediates associated with C1 versus C2 pathways, while density functional theory simulations (DFT) provide mechanistic insights into energy barriers, emphasizing how size and facet orientation govern electrochemical CO₂ reduction reaction (CO₂RR) performance. These findings offer a new approach to overcoming static system limitations by optimizing Cu nanocrystal properties, paving the way for rational catalyst design without the need for additives or complex modifications.