Template-guided synthesis of Co nanoparticles embedded in hollow nitrogen doped carbon tubes as a highly efficient catalyst for rechargeable Zn-air batteries

Rational design and construction of highly efficient and durable non-noble-metal bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial to promote the widespread implementation of rechargeable Zn-air batteries. Herein, a bifunctional catalyst comprising Co nanoparticles uniformly embedded in hollow nitrogen doped carbon tubes (Co@hNCTs) is fabricated by a facile tube-directed templating strategy. In this strategy, surfactant-treated polypyrrole (PPy) nanotubes serve as the structure-guiding templates for efficient capture of Co2+, realizing the in-situ growth of zeolitic imidazolate frameworks-67 (ZIF-67) nanocrystals on PPy nanotubes. Sodium laurylsulfonate acts as anionic surfactant to endow PPy nanotubes with functional electronegative surface and strong anchoring effect toward ZIF-67, playing the pivotal role in binding of ZIF-67 nanocrystals with PPy nanotubes potently. Consequently, the developed catalyst presents a superior ORR activity with the half-wave potential of 0.87 V excellent durability with only a 7 mV loss of half-wave potential after 5000 cycles. The catalyst also exhibits superior catalytic performance for OER. When serving as an air electrode in Zn-air batteries, a large power density of 149 mW cm−2 and long-term cyclability for over 500 h are realized in ambient air, implying the great potential in practical application. One dimensional Co nanoparticles embedded in hollow nitrogen doped carbon tubes (Co@hNCTs) catalysts with hierarchical pore structure were successfully fabricated through a facile tube-directed templating strategy. The designed Co@hNCTs catalyst exhibits impressive bifunctional oxygen electrocatalytic performance for rechargeable Zn-air battery. [Display omitted] •Co nanoparticles uniformly embedded in hollow nitrogen doped carbon tubes.•The sample exhibits high specific surface area with hierarchically pore structure.•Polypyrrole nanotubes serve as skeleton to promote the dispersion of ZIF-67.•Remarkable electrocatalytic activity and stability for ORR and OER.