缺陷调控石墨烯复合催化剂在氧还原反应中的作用

电化学氧还原反应(ORR)在能源、催化等领域具有广阔的应用前景, 因此开发性能优异、选择性高的催化剂对于促进ORR发展具有重要意义。ORR反应按照反应过程可以分为二电子反应过程和四电子反应过程。本研究以化学修饰石墨烯为原料, 通过调控其表面缺陷并与银-对苯二琨二甲烷(Ag-TCNQ)纳米点复合, 合成了不同缺陷程度的复合催化剂, 在此基础上比较了Ag-TCNQ/高缺陷石墨烯和Ag-TCNQ/低缺陷石墨烯的ORR性能。研究结果显示Ag-TCNQ/高缺陷石墨烯催化ORR的电子转移数为2.4, 双氧水产率达0.62 mg/h, 法拉第效率为64.45%。相比之下, Ag-TCNQ/低缺陷石墨烯参与ORR的电子转移数为3.7, 氧还原半波电位约为0.7 V(vs. RHE)。因此, 高缺陷催化剂促进ORR的二电子过程, 而低缺陷的催化剂促进ORR的四电子过程。在复合材料中, Ag-TCNQ纳米颗粒和石墨烯发挥了各自的结构优势, 形成复合效应, 共同提高了催化活性。

Defect Engineering of Graphene Hybrid Catalysts for Oxygen Reduction Reactions

Oxygen reduction reaction (ORR) is important for energy and catalytic applications. Therefore, it is significant to develop highly active and selective catalysts to promote ORR. According to the reaction process, ORR can be categorized into two- and four-electrons transfer pathways. In this work, chemically modified graphene sheets with different defects were used as precursors, which were integrated with Ag-7,7,8,8-tetracyanoquinodimethane (Ag-TCNQ) to form hybrid catalysts. The ORR activities of Ag-TCNQ/high defect graphene and Ag-TCNQ/low defect graphene were compared. The results show that the electron transfer number of ORR with Ag-TCNQ/high defect graphene is 2.4. And its corresponding production yield of H₂O₂ is 0.62 mg/h, and Faraday efficiency is 64.45%. In comparison, the electron transfer number of ORR with Ag-TCNQ/low defect graphene is 3.7 and the corresponding half-wave potential is about 0.7 V (vs. RHE). Therefore, high structural defects promote the two-electron process of ORR, while low structural defects facilitate the four-electron process of ORR. In the composites, Ag-TCNQ nanoparticles and graphene have formed a hybrid effect to improve the catalytic activities.