Electrochemical CO2 reduction to C2+ species: Heterogeneous electrocatalysts, reaction pathways, and optimization strategies

Electrochemical CO2 reduction to fuels and chemicals using renewable electricity offers a green and efficient tool/strategy to mitigate global warming and energy supply problems. Relative to C-1 products, C2+ hydrocarbons and oxygenates containing two or more carbon atoms have higher energy densities. Also, many multi-carbon products are chemical feedstocks in high demand. However, C-C bond formation competes with the H-H and C-H bond formation. H-H and C-H bonds have stronger bond energies and thus require lower energies for their formation than C-C bonds. Therefore, to increase C2+ fuel selectivity and yield requires the design of advanced tailor-made electrocatalysts and electrolytes as well as optimization of electrochemical cells. An overarching aim of this article is to comprehensively summarize recent advances on the electrocatalytic conversion of CO2 to C2+ hydrocarbons (oxygenates) over various materials. The fundamentals of CO2 catalysis and possible C-2(+) reaction pathways are provided. We highlight strategies available for improving C2+ compound production. (C) 2018 Elsevier Ltd. All rights reserved.