Regulation of graphitized pore structure adjacent to atomic Fe[sbnd]N4 sites with pyrolyzing rate for highly active oxygen reduction reaction electrocatalysts

Abstract

Non-noble metal monatomic ORR catalysts supported on carbon materials have drawn extensive attention for their maximum atomic activity utilization and high electrocatalytic efficiency. The pore structure of carbon carriers and rational design of efficient active sites are still one of the most serious challenges. Here, by regulating the graphitization of the pores surrounding FeN4 sites with a rapid pyrolyzing rate, we synthesized a nanosheet Fe-N4@graphitized porous carbon catalyst (Fe-N4@GPC) that exhibits higher ORR activity (E1/2 of 0.891 V) and cyclic stability (5000 cycle decay 11 mV) than commercial Pt/C catalyst in alkaline electrolyte. In addition, the assembled primary zinc-air battery has a superior performance (open circuit potential of 1.47 V and power density of 205.7 mW cm−2) than Pt/C catalyst (1.45 V, 199.6 mW cm−2). Compared with the FeN4 catalyst fabricated at a regular pyrolyzing rate, Fe-N4@GPC feature isolated FeN4 active sites surrounded by rich graphitized pores on nanosheets, which facilitates the electron and molecular-ionic transfer and thereby promoting the ORR performance. Therefore, this study highlights the significance of pyrolyzing rate regulation in modulating the graphitization of pores adjacent to the FeN4 active sites, which contributes to developing rational design and synthesis of efficient carbon-based monatomic catalysts in the future.