Abstract

It is of great significance to develop the highly active, durable and inexpensive oxygen reduction reaction (ORR) electrocatalysts for fuel cells and metal-air batteries. Nitrogen-doped carbon nanotube (NCNTs) was considered to be one of the most significant non-noble metal ORR electrocatalysts, but its catalytic activity has some shortcomings due to its unfavorable ORR intermediates adsorption characteristics. Herein, we report a new kind of nitrogen-doped carbon nanotubes, which have filled with Fe3C nanowires (NCNTs@Fe3C NWs), working as a stable and effective ORR catalyst. The half-wave potential of the obtained catalyst in a 0.1 M KOH solution is 0.88 V, which is significantly higher than the pristine NCNTs (0.79 V) and the commercial Pt/C (0.85 V). Compared with NCNTs, the improvement in ORR activity of NCNTs@Fe3C NWs can be attributed to the strain effect on the outermost carbon layer due to the high filling of Fe3C NWs. Most importantly, NCNTs@Fe3C NWs shows higher durability and better methanol tolerance than the commercial Pt/C catalyst. Density functional theory (DFT) calculation shows that the tensile strain can optimize the binding energy of ORR intermediates to a certain extent. This work provides new research ideas for the rational design of high-efficiency carbon-based ORR electrocatalysts through the direction of strain engineering.

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