双功能
过电位
材料科学
电催化剂
碳纤维
催化作用
化学工程
析氧
无机化学
碳化
化学
物理化学
有机化学
电极
电化学
复合材料
工程类
复合数
扫描电子显微镜
作者
Yao Li,Jiahuan Li,Ying Dai,Xuerui Li,Chunguang Shao,Yubo Sun,Rongyue Wang,Jinlong Zou
标识
DOI:10.1016/j.mtener.2021.100737
摘要
Zeolite imidazole framework-67 (ZIF-67) derivatives are increasingly used for oxygen reduction and evolution reactions (ORR/OER). Many fundamental issues concerning their structure-bifunctional activity relationships still remain unknown. Here, we use nitrogen-doped carbon nanospheres (NCS) to support ZIF-67-derived Co3O4@carbon to obtain Co3O4@Z67/NCS catalysts with the assistance of polyvinylpyrrolidone. Carbonization temperatures have great effects on the structure and active-component changes of Co3O4@Z67/NCS. Co3O4@Z67/NCS-850 (850 °C) with the Co2+/Co3+ ratio of 1.58 shows the promising bifunctional (ORR/OER) activity (ΔE = Ej=10 (1.55 V)-E1/2 (0.812 V) = 0.738 V) and long-term stability via the 4e− process in alkaline electrolytes. Co3O4@Z67/NCS-850 exhibits a comparable half wave potential of 0.812 V with a better ORR durability (an activity decline of 16.3% after 30,000 s) and methanol resistance, by comparing with commercial Pt/C (0.817 V and 29.1%). For OER, Co3O4@Z67/NCS-850 obtains a low overpotential of 0.32 V at 10 mA/cm2 and a low charge transfer resistance of 9.69 Ω. The active-sites (Co2+ (ORR) and Co3+-CoOOH (OER)) on Co3O4 are well protected by carbon shell (Z67), which can hinder the fast deactivation (corrosion and agglomeration) of Co3O4 during electrocatalysis. The high porosity (387.88 m2/g) of Z67/NCS-850 should facilitate the mass transfer through the pores to promote the in situ electrochemical O2 reduction/evolution on the Co and/or N active sites. These results not only find the relationships between structure/components and ORR/OER activities but also indicate a direction on promoting ZIF-derived catalysts.
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