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 Co2+ and P(AA-AM) copolymer. The resultant DC hydrogel can benefit the Co2+ 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(2) g(-1)), significantly larger than that of the PAA-Co-N catalyst (10.59 at%/746 m(2) g(-1)) 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-1/2) approximate to 0.820 V versus the reversible hydrogen electrode (RHE)) and stability (approximate to 4 mV shift in E-1/2 after 5000 potential cycles in 0.5 m H2SO4 at 60 oC) relative to PAA-Co-N, which is higher than most Co-N-C catalysts reported so far.