Low temperature route to Co, N, O tri-decorated carbon nanotubes: Moderate defects toward boosted bifunctional oxygen electrocatalysis and Zn-air batteries

This work develops a simple method to Co, N, O tri-decorated carbon nanotubes (CNTs) prepared at a low temperature of 200 degrees C as highly bifunctional catalysts towards oxygen reduction reaction (ORR)/oxygen evo-lution reaction (OER) and Zn-air batteries. The well-decorated Co, N and O surface species result in defects in CNTs supports and further tune the key features of their valence bands (such as valence band edges and relative contents of p-pi state) and finally determine ORR/OER intrinsic activity (specific activity js). Defects with a moderate of ID1/IG ratio is favorable to optimize ORR/OER intrinsic activity (-12.80 mu A cm-2BET of ORR js and-171.69 mu A cm-2BET of OER js) and bifunctional activity (0.695 V of Delta EOER-ORR) for Co(0.1)-N(6.75)-CNTs-200. It also promotes solid-state Zn-air batteries with excellent battery performance, such as high specific capacity of-800.7 mAh gZn-1(@ 25 mA cm-2,-97.6 % of the theoretical one), high energy density of-959.2 W h kg-1 (@ 25 mA cm-2,-70.9 % of the theoretical one) and long stable discharging-charging of-224 h (@ 25 mA cm-2). This work paves a route to highly efficient catalysts for oxygen electrocatalysis and Zn-air batteries at relatively lower temperatures.

Automated summary

This study develops a simple method to prepare Co, N, O tri-decorated carbon nanotubes (CNTs) as highly efficient catalysts for oxygen reduction/evolution reactions and Zn-air batteries at a low temperature of 200 degrees C. The well-decorated Co, N, and O surface species introduce defects in the CNTs supports, which further tune the key features of their valence bands and determine their intrinsic catalytic activity. These decorated CNTs show optimized intrinsic activity and bifunctional activity, as well as excellent performance in solid-state Zn-air batteries. This work paves the way for efficient oxygen electrocatalysts and Zn-air batteries at relatively lower temperatures.