A research group led by Prof. XIAO Jianping from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) and their collaborators synthesized a single-atom Pb-alloyed Cu catalyst (Pb₁Cu), which showed  high activity for the electrochemical CO₂ reduction reaction (CO₂RR) with a selectivity of 96% to formate and stability of up to 180 h at 100 mA cm^-2. 

This study was published in Nature Nanotechnology on Sept. 16. 

The researchers reported multi-path for CO₂ reduction to formate, namely the reaction paths through COOH* and HCOO* intermediates. The reaction phase diagram was built based on the "energy global optimization" approach, describing the activity trend for CO₂RR to formate. A double-peak activity trend was obtained owing to the consideration of multi-path. 

They found that Cu preferred the COOH* path, resulting in the production of hydrocarbons and oxygenates, which exhibit limited selectivity and activity toward a specific product. However, Pb₁Cu preferred the HCOO* path. The optimal HCOO* binding energy in Pb₁Cu revealed either high activity or selectivity to formate via CO₂RR. The agreement between experimental and theoretical activity trend confirms the reliability of multi-path mechanism. 

The Cu site on the Pb₁Cu step surface, rather than the single-atom Pb site, showed the highest CO₂RR activity toward exclusive formate production. The free-energy diagram with the calculated electrochemical barriers also confirms the formate selectivity. 

"The 'double-peak' describes a more accurate activity trend for CO₂RR, providing a significant insight for catalyst design," said Prof. XIAO.