A Study On Synthesis Of Pt-Cu Alloy Nanowires Networks And Their Catalytic Oxidation Performance For Ethylene Elycol

It is always an important research topic to research a catalyst with high catalytic activity,stability and low cost for the direct fuel cells.Pt is commonly used for catalysts because of its superior catalytic properties.However,monometallic Pt is particularly vulnerable to be poisoned during the catalytic process.Introducing some transition metals into Pt crystal to form alloy,cannot only effectively improve its catalytic performance,but also reduce the cost.In recent years,Pt-Cu alloy nanomaterials have been widely concerned.The research results showed that its catalytic performance could be greatly improved due to the synergistic effect between Pt and Cu when Pt and Cu form an alloy.In addition,alloy nanowires(NWs)possess high specific surface area,and the one-dimensional continuous linear structure is conducive to transfer mass and electron.So they become a hot spot of research in the field of catalytic materials.At present,among numerous synthesis methods of NWs,the chemical reduction is a good promising method due to its simple,easy to operate,uniform products,and high reproducibility.However,the previous work mainly focused on the synthesis,characterization and catalytic application of NWs,while little attention has been paid to carry out a systematic study on the relationship of the composition with properties of alloy NWs.In present paper,Pt-Cu alloy NWs was successfully prepared by chemical co-reduction method of NaBH4 at room temperature.The morphology,formation mechanism,composition and crystal structure of Pt-Cu NWs were characterized by SEM,TEM,EDS and XRD.At the same time,the formation mechanism and electro-catalytic performance of Pt-Cu alloy NWs was studied.The main conclusions are gained as follows:(1)Pt/Cu ion ratios had a distinct effect on the morphology and size of NWs.In present synthesis system,the NWs could not be formed for single metal Pt,but NWs could be formed when the coexistence of Pt and Cu in precursor.The diameter of NWs gradually decreased with Pt/Cu ion ratio reducing.The high quality and uniform NWs networks could be obtained when the molar ratio between the reducing agent and the metal ion was controlled to 5 and glucose was added to 15 mmol·dm-3.The Pt-Cu NWs grew based on the mechanism of lattice-matched oriented attachment.The glucose not only played the role of one-dimensional growth directing agent,also the stabilizing agent.(2)The composition of Pt-Cu alloy NWs was tuned by adjusting the ratio of PtCl62-/Cu2+ in the precursor,and the metal ion ratio was linearly proportional to the composition of the NWs.Pt-Cu NWs possessed the typical face-centered cubic(fcc)alloy phase structure.The NWs grew along the(111)plane orientation of Pt-Cu alloy.Both of Pt and Cu elements were homogenously distributed throughout the whole NWs networks.(3)The catalytic activity of Pt-Cu alloy NWs were strongly determined by their composition.Pt31Cu69NWs demonstrated the highest catalytic activity,which was about 1.8 times higher than commercial Pt/C catalyst.Meanwhile,Pt31Cu69 NWs could obviously improve the dynamical mechanism of ethylene glycol oxidation reaction.The electro-catalytic oxidation of ethylene glycol in alkaline medium obeyed the two parallel pathways mechanism of poisoning and non-poisoning.Pt-Cu NWs exhibited higher catalytic performance due to the bi-functional synergy between Pt and Cu.The Cu atoms in Pt-Cu NWs can remove the CO poisonous species from adjacent Pt atoms surface,thus some Pt atoms active sites can be re-liberated.