Cobalt encapsulated within porous MOF-derived nitrogen-doped carbon as an efficient bifunctional electrocatalyst for aprotic lithium-oxygen battery

In energy storage and conversion field, it is an eternal theme to develop effective and stable catalysts. Carbon composites with embedded metal/metal oxides as electrochemical catalysts has attracted extensive research attention. However, severe carbon evaporation causes the aggregation of metal particles during the pyrolysis synthesis, which directly leads to poor dispersion of the active sites and a decrease in catalytic stability. To solve this issue, cobalt encapsulated within porous nitrogen-doped carbon nano-frame (Co, N-CNF) is prepared by template-induced calcinations strategy using mental organic framework (MOF) as precursor and mesoporous SiO2 as template. This strategy leverages the template to capture volatile carbon and nitrogen species and retains the structure of the MOF precursor after pyrolysis. The prepared Co, N-CNF catalyst has a multi-layered spherical graphite shell with sp2 hybrid orbital and metallic cobalt core with fully exposed catalytic active site. Li-O-2 batteries based on this core-shell structured cobalt-encapsulated catalyst show excellent electrochemical performance, including high specific capacity (5288 mA h g(-1)) and remarkable cycle stability without significant voltage attenuation after 500 cycles. These excellent properties are attributed to the unique core-shell structure, as well as the fully exposed metallic cobalt active sites. (C) 2019 Elsevier B.V. All rights reserved.