钴盐阴离子基团对Co-N-C催化剂电催化活性的影响

摘要

采用化学氧化法在苯胺聚合过程中分别加入钴(Co)为 Co2+而阴离子基团为(C2H3O2)22-、Cl22-、(NO3)22-、SO42-及C2O42-的乙酸钴、氯化钴、硝酸钴、硫酸钴、草酸钴等钴盐,合成出不同聚苯胺-钴(PANI-Co)配位聚合物.然后将 PANI-Co 聚合物作为前驱体在N2气氛中900 ℃热处理,制备出氮掺杂的Co-N-C碳基催化剂.采用SEM、XRD、XPS、Raman等手段分析Co-N-C催化剂的形貌、结构、化学组成及化学价态,并采用电化学方法测试了 Co-N-C 催化剂的电催化活性.结果表明,Co 盐的阴离子基团对Co-N-C催化剂的形貌影响不大,但对Co-N-C催化剂中表面化学组成及含量、碳结构、石墨化程度以及Co的价态影响较大,并且Co盐的阴离子基团会影响Co-N-C催化剂的电催化活性,其氧还原(ORR)活性按照(C2H3O2)22->Cl22->(NO3)22->SO42->C2O42-顺序降低.含(C2H3O2)22-和Cl22-阴离子的钴盐制备的Co-N-C催化剂具有较高的 ORR活性,这可能源于其较高含量的石墨氮和吡啶氮.%During the process of the aniline polymerization,bivalent cobalt salt with different anionic groups such as (C2H3O2)22-,Cl22-,(NO3)22-,SO42-and C2O42- were added into the solution and then different polyaniline cobalt (PANI-Co) coordination polymer were obtained.Finally,Co-N-C catalysts were prepared through pyrolysis of PANI-Co coordination polymer. The morphology,structure,chemical composition and chemical valence of the Co-N-C catalysts were characterized by scanning elec-tron microscopy (SEM),X-ray spectroscopy (XRD),X-ray photoelectron spectroscopy (XPS)and Raman spectra (Raman).The electrocatalytic activity of Co-N-C catalysts were tested by electrochemical method.The results showed that the cobalt salt anionic groups had little impact on the morphology of Co-N-C catalysts,but had a great influence on the composition and surface chemistry of Co-N-C catalysts,carbon structure,degree of graphitization and the valence of Co.The cobalt salt anionic groups could affect the electrocatalytic activity of Co-N-C catalysts.The catalytic activities decreased as(C2H3O2)22- >Cl22- >(NO3)22- >SO42- >C2O42-.The Co-N-C catalysts prepared by cobalt salt containing (C2H3O2)22- and Cl22- anions had higher ORR activity,which possibly due to the higher content of graphite nitrogen and pyridine nitrogen.