NaNO3 assisted gelatin-derived multi-level porous carbon aerogel loaded Fe single-atom for high efficient oxygen reduction reaction

In thrall to the low productivity and expensive price of the precious metal catalysts (PMC), it is imminent to develop high-efficient non-noble metal single-atom catalysts (SACs) to replace PMC. However, thermally induced aggregation into nanoparticles and micropores-dominated structures are commonly encountered issues in loading SACs on carbonaceous supports, leading to low exposure ratio of active sites and inadequate mass transference. Herein, we fabricated a series of gelatin-derived carbon-aerogels (GDCAx) to prevent the aggregation of Fe atom and form the hierarchically porous nanonetwork, and thus the Fe SACs (Fe-N-GDCAx) with abundant and hierarchical pores are obtained after pyrolysis. The Fe-N-GDCAx has plentiful accessible Fe-Nx active sites and mass transfer pathways, benefiting to ORR procedure. The optimal sample Fe-N-GDCA0.8 without other gas assisted during annealing (only in argon atmosphere) exhibits exceedingly excellent half-wave potential (E1/2) of 0.93 V (vs. RHE) in 0.1 M KOH. Aqueous zinc-air battery assembled with Fe-N-GDCA0.8 presents ultrahigh specific capacitance of 803.4 mAh gZn−1 (close to 824 mAh gZn−1 theoretical value) and long-term stability. Meanwhile, quasi-solid zinc-air battery has high peak density and specific capacitance of 82.6 mW cm−2 and 713.2 mAh gZn−1 respectively.