Constructing Co-N-C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells.

Exploiting platinum-group-metal (PGM)-free electrocatalysts with remarkable activity and stability toward oxygen reduction reaction (ORR) is of significant importance to the large-scale commercialization of proton exchange membrane fuel cells (PEMFCs). Here, a high-performance and anti-Fenton reaction cobalt-nitrogen-carbon (Co-N-C) catalyst is reported via employing double crosslinking (DC) hydrogel strategy, which consists of the chemical crosslinking between acrylic acid (AA) and acrylamide (AM) copolymerization and metal coordinated crosslinking between Co and P(AA-AM) copolymer. The resultant DC hydrogel can benefit the Co dispersion via chelated Co-N/O bonds and relieve metal agglomeration during the subsequent pyrolysis, resulting in the atomically dispersed Co-Nx/C active sites. By optimizing the ratio of AA/AM, the optimal P(AA-AM)(5-1)-Co-N catalyst exhibits a high content of nitrogen doping (12.36 at%) and specific surface area (1397 m g ), significantly larger than that of the PAA-Co-N catalyst (10.59 at%/746 m g ) derived from single crosslinking (SC) hydrogel. The electrochemical measurements reveal that P(AA-AM)(5-1)-Co-N possesses enhanced ORR activity (half-wave potential (E ) ≈0.820 V versus the reversible hydrogen electrode (RHE)) and stability (≈4 mV shift in E after 5000 potential cycles in 0.5 m H SO at 60 ºC) relative to PAA-Co-N, which is higher than most Co-N-C catalysts reported so far.