Boosting the oxygen reduction reaction of a nonprecious metal Fe–Nx/C electrocatalyst by integrating tube-terminated edges into the basal plane of Fe- and N-codoped carbon bubbles.

The preparation of a highly efficient and economical oxygen reduction reaction (ORR) catalyst is one of the greatest challenges for the application of proton exchange membrane fuel cells (PEMFCs). Herein, we integrated tube-terminated edges into the basal plane of Fe- and N-codoped carbon bubbles to obtain an excellent Fe-N x /C ORR electrocatalyst. The synthesis of the uniformly distributed Fe- and N-codoped tube-terminated edge-dominated carbon bubble (Fe-TTNCB) was based on a new self-sacrificing template strategy. The unique micro-meso/macromorphological design endowed the Fe-TTNCB catalysts with abundant surface-terminated features to facilitate the construction of edge-hosted Fe-Nx/C active sites, thus improving the mass transport properties and promoting the accessibility of oxygen to the active sites. Due to the synergistic effects among all of the above characteristics, the Fe-TTNCB catalysts had excellent ORR catalytic activity in 0.1 M KOH electrolyte with a half-wave potential of 0.905 V (E 1/2 , V vs. a reference hydrogen electrode (RHE)), which is 62 mV higher than that of commercial 20% Pt/C (0.843 V vs. RHE). Moreover, by integrating tube-terminated edges into the basal plane of Fe- and N-codoped carbon bubbles, the kinetic current density (J k) of the nonprecious metal Fe–N x /C electrocatalyst increased from 15.38 mA cm−2 (Fe- and N-codoped carbon bubble, Fe-NCB) and 32.25 mA cm−2 (Fe- and N-codoped hybrid carbon bubble, Fe-HNCB to 56.18 mA cm−2 (Fe-TTNCB) at 0.8 V, and E 1/2 was boosted from 0.87 V (Fe- and N-codoped carbon bubble, Fe-NCB) and 0.88 V (Fe-HNCB) to 0.905 V (Fe-TTNCB). Image 1 • Unique micro-meso/macromorphological Fe-N x /C catalysts were designed. • Tube-terminated edges boosted the catalytic activity when comparing the Fe-TTNCB and Fe-HNCB ORR activity. • The Fe-TTNCB catalytic activity had a half-wave potential of 0.905 V (E 1/2 , V vs. RHE). • The J k value increased from 15.38 mA cm−2 (Fe-NCB) and 32.25 mA cm−2 (Fe-HNCB) to 56.18 mA cm−2 (Fe-TTNCB) at 0.8 V. [ABSTRACT FROM AUTHOR]