Electrochemical Carbon Dioxide Reduction to Ethylene: From Mechanistic Understanding to Catalyst Surface Engineering

Abstract

Electrochemical carbon dioxide reduction reaction (CO2RR) provides a promising way to convert CO2 to chemicals. The multicarbon (C2+) products, especially ethylene, are of great interest due to their versatile industrial applications. However, selectively reducing CO2 to ethylene is still challenging as the additional energy required for the C–C coupling step results in large overpotential and many competing products. Nonetheless, mechanistic understanding of the key steps and preferred reaction pathways/conditions, as well as rational design of novel catalysts for ethylene production have been regarded as promising approaches to achieving the highly efficient and selective CO2RR. In this review, we first illustrate the key steps for CO2RR to ethylene (e.g., CO2 adsorption/activation, formation of *CO intermediate, C–C coupling step), offering mechanistic understanding of CO2RR conversion to ethylene. Then the alternative reaction pathways and conditions for the formation of ethylene and competitive products (C1 and other C2+ products) are investigated, guiding the further design and development of preferred conditions for ethylene generation. Engineering strategies of Cu-based catalysts for CO2RR-ethylene are further summarized, and the correlations of reaction mechanism/pathways, engineering strategies and selectivity are elaborated. Finally, major challenges and perspectives in the research area of CO2RR are proposed for future development and practical applications.

Rare earth oxide based electrocatalysts: synthesis, properties and applications

“…The Haber–Bosch process alone consumes 2% of global energy, with approximately 80% of NH 3 used for urea synthesis. 349,350 The combustion of fossil fuels, fertilizer intensive agriculture and industrial emissions are the main sources of nitrate waste. Compared to nitric acid reduction in ammonia production, electrocatalytic C–N coupling and co-electrolysis with NO 3 − and CO 2 are promising alternative methods for achieving direct urea synthesis.…”

Facet Engineering of Copper for Product Specific CO2 Electroreduction

“…Experiments have proven that selective exposure of crystal facets for electrocatalysts is an effective and straightforward approach to achieve product selectivity and enhanced FE toward specific CO 2 ER products. Tuning the facet exposure of Cu could promote the multicarbon (C2+) products formation in CO 2 ER. , For example, the Cu {111} facets favor preferentially CH 4 and HCOO – , while the Cu {100} favors C 2 H 4 and Cu (110) and some high-index planes leads to C2 products like CH 3 COO – , CH 3 CHO, and C 2 H 5 OH . The origin of this selectivity trend is still inconclusive but important for fundamental understanding.…”

“…Tuning the facet exposure of Cu could promote the multicarbon (C2+) products formation in CO 2 ER. 54,55 For example, the Cu {111} facets favor preferentially CH 4 and HCOO − , while the Cu {100} favors C 2 H 4 and Cu (110) and some high-index planes leads to C2 products like CH 3 COO − , CH 3 CHO, and C 2 H 5 OH. 56 The origin of this selectivity trend is still inconclusive but important for fundamental understanding.…”

A recirculation system for concentrating CO2 electrolyzer products

“…Since the initial reports of Hori et al , 5,6 much progress has been made towards improving the efficiency of electrochemical CO 2 reduction to ethylene, particularly by tuning the microenvironment of Cu catalysts. 7–12 However, most publications in the recent literature report ethylene concentrations below 10% in electrolyzer outlet streams, even with faradaic efficiencies above 50% and current densities higher than 1 A cm −2 . In many of these reports, ethylene is actually produced at concentrations well below 1% (Fig.…”