ZIF‐Co3O4@ZIF‐Derived Urchin‐Like Hierarchically Porous Carbon as Efficient Bifunctional Oxygen Electrocatalysts

Co3O4 nanoparticles were sandwiched into interlayers between ZIF‐8 and ZIF‐67 to form ZIF‐Co3O4@ZIF precursors. Pyrolysis of ZIF‐Co3O4@ZIF yielded an urchin‐like hierarchically porous carbon (Co@CNT/NC), the thorns of which were carbon nanotubes embedded Co nanoparticles. With large specific surface area and hierarchically porous structure, as‐prepared Co@CNT/NC exhibited excellent bifunctional oxygen electrocatalytic performances. It has good ORR performance with E1/2 of 0.85 V, which exceeds the Pt/C half‐wave potential (E1/2=0.83 V). In addition, Co@CNT/NC has an OER performance close to that of RuO2. To further demonstrate the effect of Co modifying on the properties, the samples were subjected to acid washing treatment. Co‐based nanoparticles were proved to After acid washing, there was obvious loss of Co particles in Co@CNT/NC, resulting in poor oxygen electrocatalysis. So, the pyrolysis products of ZIF‐8‐Co3O4@ZIF‐67 retained large specific surface area and porous structure can be retained, and on the other hand, the carbon tube structure and original polyhedron framework. Besides, existence of Co nanoparticle@carbon nanotube provided more active sites and improved the ORR and OER performances. Pyrolysis of ZIF‐Co3O4@ZIF yielded an urchin‐like hierarchically porous carbon (Co@CNT/NC), the thorns of which are carbon nanotubes embedded Co nanoparticles. As‐prepared Co@CNT/NC exhibits excellent bifunctional oxygen electrocatalytic performances. To further demonstrate the effect of Co modifying on the properties, the samples are subjected to acid washing treatment. The active site of catalyst is further proved.