Dinuclear-site catalysts (DSCs) have drawn more and more attention from researchers due to their excellent catalytic ability through incorporating two adjacent metal atoms as the catalytic center, which helps the usage of the potential synergistic interaction. However, it's challenging to precisely synthesis diatomic sites, so as to obtain catalysts with accurate dinuclear structure.

A research team led by Prof. YAO Tao from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), collaborating with Prof. ZHU Manzhou from Anhui University and Prof. LI Yafei from Nanjing Normal University, proposed a method to synthesis uniform atomically precise Ni₂ sites. The calculated results also identified the structural evolution of dinuclear active site during electrocatalytic carbon dioxide (CO₂) reduction conditions for the first time. This work was published in the Journal of the American Chemistry Society. 

(Synthesis scheme. Image by DING Tao et al.)

To obtain the dynamic structures of catalytically active diatomic sites, the researchers chose Ni₂(dppm)₂Cl₃ (dppm referring to bis(diphenylphosphino)methane, Ph₂PCH₂PPh₂), a ligand-protected diatomic cluster, as the metal precursor to introduce the metal atoms. Then the precursor was heated together with nitrogen-doped carbon to obtain supported dinuclear Ni₂ site (Ni₂/NC).

According to the researchers, this novel catalyst exhibited superior catalyzing performance as well as stability.  

In order to figure out the real mechanism, the researchers applied operando X-ray absorption fine structure technique to measure the charge transition of specific atoms and to make conclusions on atomic level. They confirmed the atomic and electronic structural changes of dinuclear sites and discovered the dynamic bridge-oxygen adsorption to form active intermediate O-Ni₂-N₆.  

Moreover, they also conducted the density function theory calculations to provide theoretical explanations. Results suggested that the observed O-Ni₂-N₆ structure acted as the dominating reaction intermediate to form carbon monoxide (CO), leading to satisfactory selectivity and yield.