A research team led by Prof. ZENG Jie from University of Science and Technology of China (USTC), and their collaborators, realized highly selective CO₂-to-formate conversion via Pb₁Cu catalyst. The study was published in Nature Nanotechnology.

Converting CO₂ into valuable chemicals and fuels with renewable electricity offers a sustainable way toward realizing carbon neutral goals. The reported HCOOH-selective electrocatalysts, such as Bi, Sn, In, Pb and Pd, do not yield satisfactory performance in either activity or stability, and are unqualified for industrial applications. In comparison, Cu has both high activity and low cost, yet with limited selectivity.

In this work, researchers obtained single-atom alloyed Cu catalysts modified by Pb, Bi, and In through epoxide gelation approach followed by electrochemical reduction. The atomic dispersion of single atoms in the Cu matrix was then verified, indicating that the single-atom alloyed Cu catalysts were successfully synthesized.

Next, researchers evaluated the catalytic activity of single-atom alloyed Cu catalysts in electrochemical CO₂ reduction (CO₂RR) in a flow cell. They discovered that the catalysts selectively favored formate formation, and Pb single-atom alloyed Cu catalyst (Pb₁Cu) could exclusively convert CO₂ into formate (~96% Faradaic efficiency) with high activity greater than 1 A cm^-2 during the reaction.

In addition, researchers revealed that oxygen protonation was suppressed while carbon protonation was promoted during CO₂RR due to the tuning effect of isolated heteroatoms on the Cu-based catalyst. Thus, the main intermediate during CO₂RR was HCOO* instead of COOH*. The former induced the formation of formate while the latter led to formation of a series of unwanted products. It explained the mechanism of the selectivity of single-atom alloyed Cu catalysts.

Further, to eliminate the cost of separation of liquid electrolyte and products, researchers developed a solid electrolyte to directly generate pure HCOOH. As a result, the continuous preparation of pure formic acid solution for over 180h was achieved.

The study offers a new design principle for efficient Cu catalysts that selectively generate single product.

(Written by TU Bingxin, edited by TONG Xinyang, USTC News Center)