Hollow Ti3C2Tx MXene sphere-based ZIF-67 derived central radiative cobalt-tipped carbon nanotubes electrocatalysts for ORR and OER

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a key role in many renewable energy conversion and storage technologies. As the state-of-the-art ORR and OER electrocatalysts, noble-metal-based electrocatalysts suffer from high price, low earth abundance, single functionality, and poor stability. Developing high performance noble-metal-free ORR and OER bifunctional electrocatalysts as alternatives is highly desirable but remains a significant challenge. In this work, we reported a metal-organic-framework-engaged strategy for the fabrication of central radiative cobalt-tipped N-doped carbon nanotube/hollow Ti3C2Tx sphere composites (h-Ti3C2Tx@Co-NCNT), in which ZIF-67 particles were in situ grown on spherical structure composed of Ti3C2Tx nanosheets constructed with hard template PMMA and then were converted to cobalt-tipped N-doped carbon nanotubes through a pyrolysis process. The hollow Ti3C2Tx nanosheets sphere not only served as conductive scaffolds for the growth of Co-NCNT but also balanced the tradeoff between graphitization of carbon and the surface area. Benefiting from the abundant Co-N/C active sites, reasonably high graphitization of carbon and suitable surface areas, the optimized h-Ti3C2Tx@Co-NCNT manifested comparable ORR (half-wave potential of 0.843 V) and OER (overpotential of 323 mV) activities. In addition, the h-Ti3C2Tx@Co-NCNT assembled zinc-air battery exhibits superior performance beyond commercial Pt/C+RuO2. Certificating this strategy can provide great opportunity for its application in renewable conversion and storage technologies.