相转移法制备PdMo催化剂及其氧还原活性

以四丁基氢氧化铵作为相转移剂,以硼氢化钠为还原剂,利用相转移法在二氯甲烷中制备了一系列不同比例的Pd_xMo/C(Pd/Mo的原子比x=1、2、3、4、5)催化剂。透射电镜(TEM)图像显示,Pd_x Mo/C是呈2～4 nm的圆形颗粒,尺寸均匀、分散性良好。X射线衍射(XRD)结果表明,加入第二组元Mo后,Pd的晶格发生扩张,调节了 Pd的几何结构。此外,X射线光电子能谱(XPS)结果表明,相对于Pd/C,Pd_4Mo/C的Pd3d_(5/)2结合能负移了 0.50 eV,说明电负性较大的Pd从Mo吸电子,电子结构发生改变。氧还原反应(ORR)结果表明,不同比例的Pd_xMo/C催化剂活性均优于Pd/C,其中当x=4时,ORR活性最佳,其起始电位和半波电位分别为0.876和0.813 V,高于商业Pt/C的0.870和0.810 V。此外,在经过3 h的运行之后电流密度仍保留82.9%,与商业Pt/C相比具有明显的优势。

Preparation and Oxygen Reduction Activity of PdMo Catalyst by Phase Transfer Method

A series of Pd_xMo/C (atomic ratio x of Pd/Mo was 1, 2, 3, 4, 5, respectively) catalysts in dichloromethane were prepared by phase transfer method using tetrabutylammonium hydroxide as phase transfer agent and sodium borohydride as reducing agent. Trancmission electron microscope (TEM) images showed that Pd_xMo/C was 2~4 nm circular particles with uniform size and good dispersion. The X-ray diffraction (XRD) results showed that the crystal lattice of Pd was expanded by adding the second component Mo, and the lattice structure of Pd was adjusted. In addition, X-ray photoelectron spectroscopy (XPS) results show that compared with Pd/C, the binding energy of Pd3d_5/2 for Pd₄Mo/C was shifted by 0.50 eV to the lower direction, indicating that Pd with higher electronegativity absorbs electrons from Mo, and the electronic structure changes. The results of oxygen reduction reaction (ORR) showed that the activity of different ratios of Pd_xMo/C was better than that of Pd/C, and the ORR activity was the best when x=4. The initial oxidation potential and half-wave potential were 0.876 and 0.813 V, respectively, which were higher than that of 0.870 and 0.810 V of commercial Pt/C. In addition, the current density retained 82.9% after 3 h of operation, showing a significant advantage over commercial Pt/C.