In the recent years, significant progress has been made toward designing active and selective catalysts for electrochemical CO 2 reduction, with particular interest focused on the two major C2 productsethylene and ethanol. Numerous efforts have been made to enhance the understanding of the heterogeneous copper-based CO 2 reduction mechanisms by computational studies. Here we provide a critical assessment of various proposed scenarios of the initial and post C−C coupling steps that result in either ethylene or ethanol. In silico rationalization of the parameters controlling the product selectivity, such as the catalyst structure and composition (Cu facets, the presence of defective sites and/or subsurface oxygen atoms, or the interplay with a second metal) and the reaction conditions (pH, applied potential, and electrolyte), is provided. A comprehensive scheme combining the proposed pathways is derived, and the issues that are still under debate and require further investigations are highlighted.

The active sites for propane dehydrogenation in Ga/H-ZSM-5 with moderate concentrations of tetrahedral aluminum in the lattice were identified to be Lewis-Brønsted acid pairs. With increasing availability, Ga and Brønsted acid site concentrations changed inversely, as protons of Brønsted acid sites were exchanged with Ga. At a Ga/Al ratio of 1/2, the rate of propane dehydrogenation was 2 orders of magnitude higher than with the parent H-ZSM-5, highlighting the extraordinary activity of the Lewis-Brønsted acid pairs. Density functional theory calculations relate the high activity to a bifunctional mechanism that proceeds via heterolytic activation of the propane C-H bond followed by a monomolecular elimination of H and desorption of propene.

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Electrochemical CO 2 reduction presents a sustainable route to storage of intermittent renewable energy. Ethanol is an important target product, which is used as fuel additive and as a chemical feedstock. However, electrochemical ethanol production is challenging as it involves the transfer of multiple electrons and protons alongside C−C bond formation. To date, the most commonly employed and effective catalysts are copper-based materials. This review presents and categorizes the most efficient and selective Cu-based electrocatalysts, which are divided into three main groups: oxide-

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