配体对钯纳米催化剂的形成及其电活性的影响

Effect of Ligands on Formation and Electroactivity for Ethanol Oxidation of Pd Nano-Catalysts

分别在EDTA,甘氨酸(Gly)和木质素磺酸钠(Ls)存在下,以硼氢化钠为还原剂,将Pd2+还原为Pd纳米颗粒并负载在多壁碳纳米管(MWCNT)表面。采用扫描电镜(SEM),透射电镜(TEM)和X射线衍射(XRD)对纳米Pd催化剂的形貌和微结构进行了表征。结果表明:EDTA存在时,所形成的Pd纳米颗粒(Pd-EDTA/MWCNT)的粒径更小,在MWCNT上的分散度更高。采用循环伏安(CV)和计时伏安技术(CA),研究了催化剂在碱性环境中对乙醇的电催化活性。在碱性溶液中对乙醇氧化的电化学研究表明:在Pd-EDTA/MWCNT催化剂上,乙醇氧化反应的起始电位较低,电流密度最大,电子传递阻力较小,反应速率较大,并且对乙醇氧化的电催化活性保持稳定。

Multi-walled carbon nano-tube（MWCNT）-supported palladium nano-catalysts（Pd-EDTA/MWCNT, PdGly/MWCNT and Pd-Ls/MWCNT） were prepared by supporting Pd nano-particles on MWCNT. The Pd nanoparticles were obtained from reduction of Pd2 ＋with Na BH4 as the reducing agent in the presence of EDTA,Glycine（Gly）, and sodium lignin sulfonate（Ls） as the ligand, separately. The catalysts were characterized by SEM,TEM and XRD. The electrochemical activity of the catalysts towards ethanol oxidation in alkaline media was examined by cyclic voltammetry（CV） and chronoamperometry（CA）. The characterization results show that the Pd-EDTA/MWCNT catalyst exhibits a smaller particle size and a better dispersity of Pd nanoaprticles compared to the Pd-Gly/MWCNT and Pd-Ls/MWCNT catalysts. As for the ethanol oxidation in alkaline media, the PdEDTA/MWCNT catalyst exhibits a lower onset potential, a higher current density, a smaller electron transfer resistance, a larger reaction rate, and more stable oxidation current, in comparison with the other two catalysts.