A Study On The Synthesis Of PtCu Alloy Nanowires And The Electrocatalytic Performance For Methanol

The ability to impart Pt-based catalysts with high catalytic activity and low cost is essential for advancing fuel cell technologies. When applied in methanol oxide reaction, monometallic Pt is easy to be poisoned by the adsorption of COad intermediate, and then resulted in lower catalytic activity. It becomes an important issue to study the Pt catalyst with high stability. When two different metals formed alloy, the catalytic activity and stability of the catalyst can be effectively improved due to the combination of synergistic effect and electronic effect. Recently, PtCu alloys nanomaterials have been under the spotlight. Research shows that when the Pt and Cu alloyed, the catalytic performance of single metal Pt can be greatly improved, and the stability and resistance to CO toxic of PtCu alloy catalyst were also improved. In addition, due to the high specific surface area and the nanowire structure is conducive to mass & electron transfer during catalytic process, the alloy nanowire material is also a hotspot in the field of catalytic materials. In numerous synthesis methods of nanowires (NWs), solvothermal method has a very good prospect because it is easy to handle and control, without involving any template or external field. The Pt, PtAu, PtPd, PtCu and PtNi nanowire materials have been successfully synthesized by the method. However, the previous work focused on the synthesis, characterization and catalytic application of NWs, little study in the physical properties with different composition, also lack the exploration of catalytic mechanism.This article describes the synthesis of composition-tunable PtCu alloy NWs of ultrathin diameters. The alloy nanowire synthesis condition, growth mechanism, the relationship between the catalytic activity & stability and component, and the catalytic mechanism has been studied by using an array of analytical techniques such as EDX, SEM, TEM, XRD, XPS and electrochemical measurement. The results are as follows:(1) The best synthesis condition of PtCu NWs:500 mg KOH, EG/DMF ratio is 4:6, reaction temperature is 170?, reaction time is 8 h. The growth mechanism of PtCu NWs is the oriented lattice growth mechanism.(2) The diameter of individual PtCu nanowire is about 1.3 nm, that of nanowire bundles is about 25±9nm. The bimetallic NWs exhibit face-centered cubic alloy phase structure. Its composition can be controlled by adjusting the Pt and Cu ions ratio of the precursor solution. Composition of the NWs changed linearly with ion ratio of the precursor solution.(3) The electrocatalytic properties of the PtCu alloy NWs for methanol oxidation reaction were shown to display an intriguing composition-dependent catalytic synergy. The maximum mass activity for Pt32Cu68 NWs was about 707 mA·mg-1. It also exhibited the highest stability and tolerance to CO poisoning.(4) The enhanced activity and stability were attributed to a bifunctional synergy whereby the alloyed Cu atoms in the Pt lattice provides CO-maneuvering sites for reducing the poisoning effect of CO intermediate species on the active surface sites of the NWs and improving the catalytic performance.