Nitrogen-Doped Mesostructured Carbon-Supported Metallic Cobalt Nanoparticles for Oxygen Evolution Reaction

A series of metallic cobalt nanoparticles supported on mesostructured nitrogen-doped carbons was successfully synthesized through soft-templating by using poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a structure directing agent. The formation of metallic cobalt nanoparticles and nitrogen-doping into carbon structures were simultaneously achieved by ammonia treatment. The physicochemical properties of the resulting materials and consequently their performance for the oxygen evolution were systematically altered by varying the cobalt loading (5–89 wt %), pyrolysis atmosphere (argon or ammonia), and temperature (600–800 °C). Thereby, up to 37 wt % of the cobalt nanoparticles were confined in the pores of the mesostructured nitrogen-doped carbon materials with a high BET surface area. At temperatures above 700 °C, the cobalt additionally catalyzes the graphitization of the carbon support. The catalyst with a cobalt loading of 37 wt % pyrolyzed at 700 °C under an ammonia atmosphere shows the highest turnover frequency (TOF) of 311 h^–1 in the oxygen evolution reaction due to the improved electronic properties of the carbon support from the incorporation of nitrogen atoms combined with a large amount of accessible cobalt sites. This class of materials shows even higher activity in comparison with ordered mesoporous Co₃O₄.