碳纳米管负载的纳米Pd-Ag催化剂对乙醇和丙醇氧化的电化学活性

在乙二醇和水混合溶剂中，采用硼氢化钠还原的方法制备了多壁碳纳米管（MWCNT）负载的Pd和Pd-Ag纳米颗粒催化剂；在碱性介质中，用循环伏安法测试了这些催化剂对乙醇、正丙醇和异丙醇的电氧化性能。结果表明，Pd和Pd-Ag纳米颗粒均匀地分散在MWCNT表面；Pd/MWCNT、Pd₄Ag₁/MWCNT、Pd₂Ag₁/MWCNT和Pd₁Ag₁/MWCNT催化剂上金属颗粒的平均粒径分别为7、4、7和11 nm。相比乙醇和异丙醇，所制备的催化剂对正丙醇的氧化表现出较大的电流密度。与Pd/MWCNT催化剂相比，双金属Pd_nAg₁/MWCNT（n=4、2、1）催化剂，尤其是Pd₄Ag₁/MWCNT上的电流密度更大，表明Ag的加入提高了Pd催化剂对醇氧化的电化学活性，其原因是因为醇氧化过程所产生的中间体物种在双金属Pd-Ag/MWCNT催化剂上的吸附力有所减弱。

Catalytic activity of Pd-Ag nanoparticles supported on carbon nanotubes for the electro-oxidation of ethanol and propanol

Pd and Pd-Ag nanoparticles supported on multi-walled carbon nanotubes (MWCNT) were prepared by using the NaBH₄ reduction method in a mixed solvent of ethylene glycol and water; their catalytic activity for the electro-oxidation of ethanol, n-propanol and iso-propanol was investigated in alkaline media by the voltammetric method. The results indicate that Pd and Pd-Ag nanoparticles are well-dispersed on the surface of MWCNTs and the average sizes of metal particles on the Pd/MWCNT, Pd₄Ag₁/MWCNT, Pd₂Ag₁/MWCNT and Pd₁Ag₁/MWCNT catalysts are 7, 4, 7 and 11 nm, respectively. Over these catalysts, the electro-oxidation of n-propanol exhibits larger current density than the oxidation of ethanol and iso-propanol. Moreover, the binary Pd_nAg₁/MWCNT catalysts (n=4, 2, 1), especially Pd₄Ag₁/MWCNT, gives higher current density for the oxidation of ethanol and propanols than the Pd/MWCNT catalyst, suggesting that the addition of Ag can enhance the activity of Pd-based catalyst for the electro-oxidation of alcohols. The excellent activity of binary Pd-Ag/MWCNT catalysts is probably attributed to the weak absorption of intermediate species on Pd due to the interaction between Pd and Ag, which may promote the oxidation of alcohols.