Co(CN)3 catalysts with well-defined coordination structure for the oxygen reduction reaction

Metal-nitrogen-doped carbon (M-N-C) catalysts are promising platinum group metals alternatives for fuel cell cathodes; however, their randomly formed, unpredictable coordinations complicate any structure–property investigation and lead to low active site density. Here we achieve dense and well-defined cobalt sites on the surfaces of Co(CN) 3 microcrystals, which are identified by single-crystal X-ray diffraction and X-ray absorption spectroscopy. In situ infrared spectroscopy and density functional theory calculations elucidate that the high oxygen reduction reaction performance (half-wave potential is 0.90 V versus RHE) of the cubic Co(CN) 3 is due to its tailored coordination environment that optimizes *OH desorption. The cyanide linkage with minimized spacing between cobalt atoms maximizes active sites’ spatial density, which boosts the anion-exchange membrane fuel cell peak power density to 1.67 W cm −2 . The microcrystals with well-defined coordination structures can be used as Co-N-C analogues for their structure–property relationship investigations.