PtPb/ C 催化剂的制备及其对甲酸电氧化的催化性能

目的通过Pb元素的添加来提高Pt/C催化剂电催化氧化甲酸的性能。方法通过乙二醇协助硼氢化钠还原法,以氯铂酸为Pt源和硝酸铅为Pb源制备不同原子比的PtxPb/C催化剂。采用X射线衍射光谱法(XRD)和透射电子显微镜技术(TEM)表征样品的晶体结构和颗粒形貌;采用循环伏安法表征样品催化氧化甲酸的性能。结果利用乙二醇协助硼氢化钠还原法成功制得了Pt和Pb原子比不同的PtxPb/C催化剂,XRD和TEM测试结果表明这些样品均为Pt的面心立方结构,且颗粒大小均一、分散均匀,其平均粒径为4 nm左右。循环伏安测试结果表明PtxPb/C催化剂催化氧化甲酸的性能优于商业Pt/C催化剂的催化性能,且受Pt和Pb原子比的影响,当原子比为5∶1时,其对氧化甲酸的催化性能最好,峰电位对应的Pt的比质量活性达到2000 m A/(mg Pt),远远高于商业Pt/C,同时计时电流曲线表明其具备良好的稳定性。结论 Pb原子的加入影响了Pt原子的电子结构,与Pb对Pt的协同作用共同促进了CO等中间产物在Pt表面的快速氧化,降低了催化氧化甲酸的初始电位,促使甲酸在低电位直接氧化为CO2和H2O,提高了其催化氧化甲酸的峰电流,有效减轻了Pt中毒,提高了其催化活性。

Preparation of PtPb/ C Catalyst and Its Electro-oxidation Catalytic Performance for Formic Acid

ABSTRACT:Objective To improve the electro-oxidation catalytic performance of Pt/C catalyst for formic acid by adding the Pb element. Methods The Ptx Pb/C catalysts with different atomic ratios were prepared by an ethylene glycol-assisted NaBH4 reduction method. The structure and morphology of the catalyst were characterized by X-ray diffraction ( XRD) and transmission electron mi-croscopy ( TEM) , electrochemical performances were investigated by cyclic voltammetry. All electrochemical measurements were carried out in a conventional three-electrode electrochemical cell at 25 ℃ using cyclic voltammetry (CV) on a CHI 760B. Results The results of XRD and TEM showed that all prepared catalysts displayed typical character of Pt face center cubic phase with an av-erage size of Pt nanoparticles at 4 nm which had an uniform dispersion on carbon support. The Ptx Pb/C catalysts had better electro-catalytic activity for formic acid electrocatalytic oxidation than that of JM-Pt/C. The electro-catalytic activity was affected by the a-tomic ratios of Pt and Pb. In addition, when the atomic ratio was 5 : 1, the PtxPb/C catalyst showed the highest peak current den-sity ( mass activity) of 2000 mA/mg Pt with better stability. Conclusion The adding of Pb atoms affects the electronic structure of Pt atoms. With the assistance of Pb to Pt, the rapid oxidation, such as CO, is promoted the intermediate products on the surface of Pt. In addition, the synergistic effect reduce the initial electric potential of catalyzing oxidation formic acid, promote formic acid di-rectly oxidated as CO2 and H2 O, improve the peak current of catalyzing oxidation formic acid, effectively deduce the poisoning of Pt, and enhance its catalytic activity.