Strategies to Modulate the Copper Oxidation State Toward Selective C₂₊ Production in the Electrochemical CO₂ Reduction Reaction

Abstract

The electrochemical reduction of CO2 to form value‐added chemicals has received considerable attention in recent years. Copper (Cu) has been recognized as the only element capable of electro‐reducing CO2 into hydrocarbons with two or more carbon atoms (C2+), but the low product selectivity of the Cu‐based catalyst remains a major technological challenge to overcome. Therefore, identification of the structural features of Cu‐based catalysts is of great importance for the highly selective production of C2+ products (ethylene, ethanol, n‐propanol, etc.), and the oxidation state of Cu species in the catalysts has been found critical to the catalyst performance. This review introduces recent efforts to fine‐tune the oxidation state of Cu to increase carbon capture and produce specific C2+ compounds, with the intention of greatly expediting the advance in the catalyst designs. It also points to the remaining challenges and fruitful research directions for the development of Cu‐based catalysts that could shape the practical CO2 reduction technology.This article is protected by copyright. All rights reserved

Electrocatalytic CO2 Reduction for Dynamic C1, C2, and C3+ Chemistry over Electrodeposited Zn on Cu and CuZn Mesh Supports

“…Among various screening tests involving different electrodes and electrolytes (Figure S1), two electrodes, Zn/Cu and Zn/CuZn, were selected and tested at applied potentials in 0.1 M KHCO 3 and 0.1 M K 2 CO 3 electrolytes. The reduction products were categorized into several groups: C 1 gaseous products (CO and CH 4 ), C 2 gaseous products (C 2 H 4 and C 2 H 6 ), C 3,4 hydrocarbons, major C 1 /C 2 /C 3 liquid products (formate, ethanol, and propanol), and minor C 1 /C 2 /C 3 liquid products (methanol, acetate, acetaldehyde, and isopropanol). − In discussing the reduction products over Zn/Cu and Zn/CuZn electrodes, it was observed that bare Zn produced only H 2 , CO, and formate, with negligible amounts of C 2+ products . In contrast, bare Cu exhibited high FEs for C 2+ products (Figure S1), although propanol production was negligible under the present conditions.…”

“…The EC CO 2 reduction mechanism was inferred from the identified reduction products and established mechanistic frameworks. As mentioned earlier, the reduction products were categorized into several groups: C 1 gaseous products (CO and CH 4 ), C 2 gaseous products (C 2 H 4 and C 2 H 6 ), C 3,4 hydrocarbons, major C 1 /C 2 /C 3 liquid products (formate, ethanol, and propanol), and minor C 1 /C 2 /C 3 liquid products (methanol, acetate, acetaldehyde, and isopropanol). − Additionally, H 2 emerged as a dominant product in the EC process. The production of H 2 is a well-known and common outcome, typically proceeding via the reaction H + + e – → H*, followed by association reactions such as H* + H + + e – → H 2 and H* + H* → H 2 .…”

“…Electrochemistry (EC) has been extensively utilized in the quest for CO 2 recycling and the production of value-added products, offering promising solutions for both energy and environmental challenges. − Cu-based electrocatalysts have demonstrated superiority over other metal catalysts by exhibiting high C–C coupling efficiency, leading to the production of C 2+ (oxygenated) hydrocarbons. − They also offer a higher likelihood of yielding desired products among a range of options. In contrast, catalysts based on other metals generally offer fewer options for reduction products.…”

Revolutionizing electrochemical CO2 reduction to deeply reduced products on non-Cu-based electrocatalysts

“…, *COOH, *CO). 9 In general, non-Cu metals exhibit poor eCO 2 RR activity towards deeply reduced products due to either strong ( e.g. H 2 mainly produced on iron, cobalt, nickel) or weak ( e.g.…”