Construction of ORR/OER catalysts with Fe/Co nitride synergistic carbon nanotubes for a fast catalytic system

Excellent ORR/OER bifunctionality is the basis for zinc-air battery applications, and transition metal nitrides (TMNs) have been investigated for zinc-air battery applications due to their higher catalytic activity, lower cost, and better stability. Meanwhile, combining TMNs with nitrogen-doped carbon nanotubes (NCNTs), which have excellent electrical conductivity, makes the practical application of zinc-air batteries possible. In this work, we propose a one-pot method for preparing PPY-encapsulated Fe-ZIF-8 and a strategy of secondary pyrolytic doping of Co metal ions on this basis. During pyrolysis, the catalyst formed Co/Fe bimetallic nitrides and many highly graphitized NCNTs. We successfully constructed an electrochemical fast reaction system with Fe/Co bimetallic nitride as the main active site and NCNTs as the fast electron transport channel. The catalyst obtained after a series of experiments is denoted as Co/Fe-NCNT-2. The catalyst Co/Fe-NCNT-2 exhibited excellent ORR and OER performance (ΔE (E j=10 -E 1/2 ) of 0.615 V). Co/Fe-NCNT-2 liquid zinc-air battery cell power density and specific capacity were 128.22 mW cm −2 and 816.79 mAh g −1 , respectively. In particular, a Co/Fe-NCNT-2 liquid zinc-air battery completed 1000 (360 h) charge-discharge cycle tests at 10 mA cm −2 . And, we explored the reason for the increase of voltage gap during the battery charging and discharging. Finally, this work provides a feasible idea for Co/Fe bimetallic nitride efficiently combined with NCNTs to be applied in zinc-air batteries, which broadens the way for zinc-air batteries to be put into large-scale applications in the future.