Effect of Feature Shape and Dimension of a Confinement Geometry on Selectivity of Electrocatalytic CO₂ Reduction

The local confinement effect, which can generate a high concentration of hydroxide ions and reaction intermediates near the catalyst surface, is an important strategy for converting CO₂ into multi-carbon products in electrocatalytic CO₂ reduction. Therefore, understanding how the shape and dimension of the confinement geometry affect the product selectivity is crucial. In this study, we report for the first time the effect of the shape (degree of confinement) and dimension of the confined space on the product selectivity without changing the intrinsic property of Cu. We demonstrate that geometry influences the outcomes of products, such as CH₄ , C₂ H₄ , and EtOH, in different ways: the selectivity of CH₄ and EtOH is affected by shape, while the selectivity of C₂ H₄ is influenced by dimension of geometry predominantly. These phenomena are demonstrated, both experimentally and through simulation, to be induced by the local confinement effect within the confined structure. Our geometry model could serve as basis for designing the confined structures tailored for the production of specific products.