双功能yolk-shell钴@钴氮碳掺杂氧电极催化剂

以ZIF-67为模板，通过表面原位聚合多巴胺，与金属Co²⁺发生强烈螯合，释放出有机配体，得到中空的金属-有机结构材料（Co-PDA）。通过900℃高温处理得到类似蛋黄（yolk-shell）结构的金属氮掺杂碳材料（Co@Co-N/C）。这种特殊结构的材料具有优异的氧还原（ORR）和析氧反应（OER）电催化活性，在0.1 mol/L KOH电解液中，其ORR的半波电位为0.81 V，Tafel斜率为60 mV/dec；在电流密度为10 mA/cm²时，其OER过电位为390 mV，Tafel斜率为71 mV/dec，总的氧电极催化活性为0.82 V，是一种优良的双功能氧电极催化剂。

York-shell Co@Co-N/C of bifunctional oxygen electrocatalysts

ZIF-67 was used as a template for producing metal and nitrogen doped carbon composite as electrocatalysts. By an in-situ polymerization of dopamine on the surface of ZIF-67, Co²⁺ ions were extracted into the polydopamine shell due to the strong chelation between them and led to the decomposition of ZIF-67, which resulted into a hollow composite of Co-PDA. Subsequently, a yolk-shell structure of metal and nitrogen doped carbon composites (Co@Co-N/C) was obtained by a high temperature pyrolysis at 900℃. The unique structure of Co@Co-N/C provided excellent bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), repetitively. For ORR, the half-wave potential was 0.81 V and the Tafel slope was 60 mV/dec. For OER, the overpotential was 390 mV at the current density of 10 mA/cm², and the Tafel slope was 71 mV/dec. More importantly, the total oxygen electrocatalytic activity was as low as 0.82 V.