Explosion effect directly induced hierarchical carbon nanotube electrocatalyst integrated with Fe/Co dual sites for hydrogen fuel cells

Abstract

Atomically dispersed metal-site catalysts, especially those derived from high temperature calcination of zeolite-based imidazole salt framework (ZIFs), have great potential in catalyzing oxygen reduction reaction (ORR) with slow kinetics owing to their large atomic utilization and tunable coordination environment. However, ZIFs-derived carbon-based catalysts often exhibit octahedral particle morphology and thus complex post-treatment processes were usually required to modulate the pore structure of the membrane electrodes to enhance the utilization of metal-site sites in the cathode ORR of fuel cells. Herein, a highly efficient catalyst with Fe/Co dual metal sites anchored onto N-doped carbon nanotubes (CNTs) was synthesized by one-step calcination based on the explosion effect of ClO₄^- ion and Fe-Co bimetal coordination interaction, named FeCo-N-CNT. The introduction of ClO₄^- ions and Fe/Co bimetals gives the catalyst a dense reachable active site and a hierarchical porous structure. It is worth noting that the half-wave potential of the FeCo-N-CNT reached 0.9 V in an alkaline medium and showed good cyclic stability. More impressively, the FeCo-N-CNT also shows excellent ORR catalytic performance in both acid and neutral electrolytes, with a maximum power density 1.2 and 1.4 times higher than Fe-N-PC and Co-N-PC with single-metal sites in hydrogen fuel cells, respectively. This work provides a novel method for adjusting the structure of catalysts and improving the accessibility of metal-sites.