Beyond scaling relations in electrocatalysis: unifying concepts from molecular systems and metallic surfaces.

Transitioning the chemical industry away from fossil fuels is a critical goal that requires the adoption of alternative, non-fossil carbon feedstocks. The electrochemical CO reduction reaction, driven renewable-derived electricity, represents an unparalleled technology that uses CO as a C-building block to generate industrially relevant products. Although many electrocatalytic systems have demonstrated promising activities in producing a wide range of products, challenges remain in controlling the product selectivity and reducing the operating overpotential for large-scale applications. This Perspective outlines recent efforts in designing tailored microenvironments in electrocatalytic systems to boost their selectivity and energy efficiency. We review examples from homogeneous and heterogeneous systems, emphasizing mechanistic studies that elucidate how the modulation of the space surrounding catalytic active sites can control the outcome of electrocatalysis. Lastly, we carry out a thermodynamic-kinetic analysis to identify existing scaling relationships that govern the electrocatalytic performance of molecular catalysts, and we highlight examples of catalysts that circumvent these relations through the functionalization of their secondary coordination sphere.