Synthesis Of Noble Metal Nano Materials And Their Electrocatalytic Performance

The direct liquid full cells have always been attrective subjects because of their efficient energy conversion and environment-friendly feature.Noble metals,such as Pt and Pd,have been widely used as catalysts in direct liquid fuel cells early.But the expensive prices of noble metals have seriously restricted the development of fuel cells.Materials with hollow nanostructures can provide more electrochemical catalytic sites which are helpful to reduce consumption of noble metals and enhence activity of catalysts.Herein,using Ag nanowires(NWs)as sacrificial templates,one-dimensional PdAg nanotubes(NTs)and PtAg nanotubes(NTs)were synthesized via a galvanic replacement reaction approach.The morphology,shape and composition of products were characterized by TEM,XRD,EDS,and other modern detection techniques.The electrocatalytic performance of PdAg NTs and Pt Ag NTs towards methanol or ethanol oxidation reaction was also investigated.The experimental details are as follows.In a modified polyol process,Ag NWs with different diameters from 20 to 50 nm were synthesized.Controlling reaction conditions was crucial to the uniform morphology and high yield of Ag NWs.Further experiments were conducted to understand how the type of polyvinylpyrrolidone,concentration of KBr,temperature and other reaction conditions effected final products.In a galvanic replacement reaction approach,one-dimensional PdAg NTs and PtAg NTs were prepared by using Ag NWs as sacrificial templates.These obtained PdAg NTs and PtAg NTs with uniform morphology showed porous structures.The effects of experimental conditions on products were investigated,such as the concentration of noble metal precursor,type of surfactant,concentration of surfactant,and temperiture.Ethanol oxidation reaction(EOR)and durability experiments were conducted for PdAg NTs with thickness of 5~8nm.Methanol oxidation reaction(MOR)and durability experiments were performed for PtAg NTs with thickness of 4nm.These electrochemical measurements were used to evaluated the electrocatalytic performances of those as-prepared catalysts mentioned above.It demonstrated that the specific EOR activity of PdAg NTs was 4.89 times higher than that of commercial Pd/C.Pt Ag NTs showed 4.49-fold enhancement in MOR currents compared with commercial Pt/C,and 2.4-fold enhancement compared with commercial Pt blacks.Both PdAg NTs and PtAg NTs exhibited improved electrocatalytic stability.