Researchers in China led by a team from Fudan University have demonstrated the electrochemical reduction of CO₂ toward C₂₊ alcohols with a faradaic efficiency of ~70% using copper (Cu) catalysts with stepped sites. In a paper published in the journal Joule, they suggest that the results show great potential for the electrocatalytic conversion of CO₂ into value-added chemicals.

Electrochemical reduction of carbon dioxide (CO₂) is a promising approach to solve both renewable energy storage and carbon-neutral energy cycle. In order to improve the economic feasibility in applications, electrocatalytic CO₂ reduction with high activity, selectivity, and stability toward multi-carbon products should be realized. When considering highly selective electrocatalysts for CO₂ electroreduction, Cu catalysts have shown their potentials of producing multiple C₂₊ products in catalytic systems, while the selectivity among different C₂₊ products has yet to be optimized.

Here, we demonstrated a rational strategy to synthesize the Cu catalyst under a CO-rich environment to induce the growth of defect-rich sites that are best for the adsorption of CO. During the electrochemical CO₂ reduction process, these defect-rich sites enabled a high surface density of adsorbed *CO intermediates, allowing to tune the CO₂ electroreduction pathways toward the formation of C₂₊ alcohols.

—Gu et al.

Schematic of the synthesis of electrocatalysts and the subsequent CO₂RR process. (A and B) Cu-DS catalyst synthesized under a CO-rich environment favors high coverage of *CO intermediate and promotes alcohol production. (D and E) Cu-c catalyst deposited under an Ar environment promotes ethylene production due to the low adsorption density of *CO. (C and F) The electrochemical CO₂RR process where the adsorption density of *CO intermediates on catalyst surface tunes the CO₂RR selectivity of (C) Cu-DS toward ethanol or (F) Cu-C toward ethylene. Gu et al.

When powered by renewable solar or wind energy sources, the electrocatalytic CO₂ reduction reaction (CO₂RR) is a promising approach to produce value-added chemicals/fuels and store renewable energy to achieve the goal of net-zero-emissions. C₂₊ alcohols are desirable due to their high energy densities and large global market capacities.

However, the researchers noted, building alcohol-selective CO₂RR electrocatalysts is a challenge. Copper, one of the most effective catalysts toward C₂₊ products, typically favors the formation of hydrocarbons other than alcohols.

Current strategies for building alcohol-selective Cu-based electrocatalysts have achieved alcohol faradaic efficiency of ~50%; however, the authors noted, to approach industrially relevant performance metrics for CO₂-to-alcohol electroreduction, the selectivity toward alcohols needs to be improved further.

The researchers found that using a copper catalyst with defect-site-rich surfaces greatly enhanced the CO₂-to-alcohol reduction pathways.

Resources

• Gu et al. (2020) “Efficient Electrocatalytic CO₂ Reduction to C₂₊ Alcohols at Defect-Site-Rich Cu Surface,” Joule doi: 10.1016/j.joule.2020.12.011