Unraveling the local coordination effect of Cu-N-C single-atom catalysts towards CO adsorption a gas-phase cluster model approach.

The current understanding regarding how the coordination environment of single-atom catalysts supported on nitrogen-doped carbon (M-N-C SACs) regulates their reactivity remains controversial, due to the complicated surface chemistry and lack of atomic-level insights. Here we introduce an experimental modeling approach to unambiguously identify the individual contribution of the local environment to the adsorption activity of CO on Cu-N-C systems. The fundamental intrinsic activities of Cu-N-C systems with different N coordination numbers, N coordination geometries (, pyrrolic N and pyridinic N), defect sites (, armchair and zig-zag), as well as S and P dopants, towards CO adsorption can be explicitly obtained and compared at the strictly atomic level, which would be challenging to access conventional techniques in SACs research. For all kinds of coordination structures, we further identified general rules that control CO adsorption strength and experimental reaction rate. This novel approach is general and can be applied to other SAC metal and reaction systems.