【摘要】 通过浸渍还原法,以乙二醇作为还原剂,以H2PtCl6 6H2O作为Pt的前驱体制备了Cu@Pt/MWCNTs核壳型电催化剂;通过水热法,以KMnO4和Mn(NO3)2作为锰源制备了α-MnO2和β-MnO2,并把Cu@Pt/MWCNTs核壳型电催化剂与二氧化锰进行掺杂制得Cu@Pt/MWCNTs-MnO2复合材料.利用XRD,SEM,TEM对复合材料的结构和形貌进行表征,利用循环伏安测试曲线和阴极极化曲线等电化学测试方法对电催化剂的性能进行测试.结果表明,电催化剂中Cu@Pt纳米颗粒为核壳型,粒径为6～8 nm,MnO2的晶型为α-MnO2和β-MnO2;另外,Cu@Pt/MWCNTs-MnO2复合材料具有良好的催化性能,其中Cu@Pt/MWCNTs-β-MnO2电催化剂的电化学性能较好,具有较大的电化学活性面积,为71.1 m2 g-1,同时对MnO2促进氧还原的机理进行了初步探讨.更多还原

【Abstract】 The core-shell structure catalysts with reduced Pt loading and improved catalytic activity which are inter-metallic Pt electrocatalyst with a cheap transition metal core have become a critical issue in fuel cells.In this study,Cu@Pt/MWCNTs core-shell electrocatalyst was prepared through the impregnation chemical reduction method,by using ethylene glycol as the reducing agent,H2PtCl6as a precursor of Pt and CuSO4as a precursor of Cu.At the appropriate temperature and pH(adjusted by KOH/EG solution),Cu nanoparticles were reduced on the surface of MWCNTs(140 ℃,pH=10),and then Pt atoms were deposited on the surface of Cu nanoparticles(90 ℃,pH=7～8).α-MnO2and β-MnO2were prepared by hydrothermal method with KMnO4 and Mn(NO3)2 as the manganese source,the reaction time of α-MnO2 and β-MnO2 is 8 h and 72 h,respectively.The obtained manganese dioxide was doped onto Cu@Pt/MWCNT under ultrasound to make Cu@Pt/ MWCNTs-MnO2composite catalysts.The structure and morphology of Cu@Pt/MWCNTs and MnO2were characterized by XRD,SEM and TEM,electrochemical performances were investigated by cyclic voltammetry,cathodic polarization and other electrochemical methods.In order to discuss the oxygen reduction method of Cu@Pt/MWCNTs-MnO2,RRDE(rotating ring-disk electrode) was further used to examine the catalytic oxygen reduction reactions of Cu@Pt/MWCNTs-MnO2.Our results demonstrated that the Cu@Pt nanoparticles have the core-shell structure.The diameter of the nanoparticles is about 6 ～ 8 nm.The crystal morphology of MnO2 is α-MnO2 and β-MnO2.It was also found that the Cu@Pt/ MWCNTs-β-MnO2 composite catalysts have better catalytic performance and higher electrochemical activity surface(up to 71.1 m2 g-1).The RRDE results for the ORR indicate that,the main reaction of Cu@Pt/MWCNTs-β-MnO2 catalyst is the direct reduction of O2 to H2O which is same as the mechanism of Cu@Pt/MWCNTs catalyst,both with a four-electron charge transfer.Moreover,the mechanism of MnO2-promoting effects for the oxygen reduction was also discussed in this paper.更多还原