In Situ Formation of a Highly Selective Nickel Single Atom Catalyst for Electrochemical CO₂ Reduction to CO

Nickel single atom catalysts (Ni-SACs) perform electrochemical CO₂ reduction (ECO₂R) with near-unity selectivity, making them promising new catalysts for future industrial applications. However, modern synthesis methods are long and complicated, preventing large-scale economic feasibility. This has spurred interest in finding facile, scalable electrochemical pathways to synthesize SACs at ambient temperatures. Here, we propose a mechanism where highly selective Ni-SACs are generated in situ using a Ni anode as the Ni source. In short, during activation, Ni dissolves from the anode, migrates through the membrane, and electrodeposits as Ni(0) on a nitrogen-doped carbon precatalyst. When voltage is removed, the deposited Ni disperses to active sites throughout the cathode surface. Using this method, a highly active and selective Ni catalyst is generated in situ, achieving ECO₂R selectivity of 100% at -2.4 V in chronoamperometric experiments and >90% for 7 h of operation at -2.4 V. Using post-mortem XRD, STEM, EDS, and operando EXAFS, the mechanism for successful generation of the in situ Ni-SAC was uncovered. This study takes a new look at electrochemical SAC synthesis, offering a scalable pathway that maintains the simplicity of electrodeposition techniques while converting selectivity-limiting metal clusters into single atom sites through a simple, in situ cell treatment procedure.