管径对碳纳米管负载铂催化剂氧还原的影响

摘要

A series of nanocatalysts consisting of acid treated carbon nanotubes (CNTs) with different diameters (8-15,20-30,30-50,＞50 nm) supporting platinum (Pt) nanoparticles (PtJCNTs) were synthesized via a microwave-assisted ethylene glycol method.The as-synthesized catalysts were characterized by X-ray photoelectron spectroscopy (XPS),X-ray diffraction (XRD),thermogravimetric analysis (TGA),and transmission electron microscopy (TEM).Their catalytic performances in the oxygen reduction reaction (ORR) were evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV).The experimental results showed that the diameter of the CNTs influences the particle size,loading,and dispersion of Pt NPs.Furthermore,the Pt/CNTs having different CNT diameters displayed different catalytic activities in the ORR.The catalyst Pt/CNT8,which was prepared by using CNTs with diameters ranging between 8-15 nm as the support,exhibited the highest Pt loading,catalytic activity,and stability in the ORR.The mass activity of Pt/CNT8 was determined to be 0.188 A.mg-1 at 0.9 V,which is folds higher than that of the commercially available JM Pt/C catalyst.After testing the stability for 5000 potential cycles,the negative shift (～7 mV) of the half-wave potential for Pt/CNT8 was found to be significantly lesser than that for the JM Pt/C catalyst (～32 mV),indicating superior catalytic stability.%采用微波辅助乙二醇法制备了一系列酸处理后的不同管径(8-15,20-30,30-50,＞50 nm)的碳纳米管(CNT)负载铂(Pt)催化剂(Pt/CNT).通过X射线光电子能谱(XPS)、X射线衍射(XRD)、热重分析仪(TGA)、透射电子显微镜(TEM)对所制得催化剂进行结构表征;采用循环伏安法(CV)和线性扫描伏安法(LSV)对其催化性能进行测试.结果表明,不同管径的碳纳米管对Pt的粒径、载量和分散性有一定程度影响;然而,不同CNT管径的催化剂表现出明显不同的催化氧还原反应(ORR)活性.采用管径为8-15 nm的CNT作为载体制备的催化剂(Pt/CNT8)的Pt载量最高,表现出有很好的催化活性和稳定性.Pt/CNT8在0.9 V时Pt的质量活性为0.188 A·mg-1,是商业催化剂(JM Pt/C)的2倍.经扫描5000圈稳定性测试之后,Pt/CNT8的半波电位负移(～7 mV)远远小于商业JM Pt/C半波电位的负移(～32 mY),表现出优越的催化ORR稳定性.