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. Anion-exchange membrane fuel cells are promising devices to produce electricity from green hydrogen, but the development of suitable cathode catalysts is required for their successful deployment. Now, Co(CN)3 microcrystals with cyanide linkages and well-defined coordination structures are shown to exhibit high oxygen reduction reaction performance in alkaline conditions.