丙醇和丁醇异构体在钯镍电极上的电催化氧化

β环糊精(β-CD)具有特殊的空腔结构,将β-CD修饰的多壁碳纳米管(MWCNT)涂在钛基底上,采用电沉积的方法在修饰的钛基底上沉积纳米PdNi催化剂。SEM结果表明,PdNi纳米颗粒在β-CD/MWCNT修饰的钛片上有较好的分散度,粒径为90~130 nm。在碱性溶液中,测试了PdNi-β-CD/MWCNT/Ti电极分别对丙醇和丁醇不同异构体氧化的电催化活性;通过计算与-OH相连的碳原子上的Muliken净电荷,分析不同异构体的氧化机理。结果表明,不同异构体的氧化活性不同,PdNi-β-CD/MWCNT/Ti电极对正丙醇和正丁醇的氧化活性明显高于其异构体,-OH所在碳原子上的Muliken 净电荷越小,醇类分子越容易被氧化。

Electrocatalytic oxidation of propanol and butanol isomers on palladium-nickel catalyst

β-cyclodextrin (β-CD) with a special cavity structure was firstly grafted on the surface of multi-walled carbon nanotubes (MWCNTs), which were then immobilized on Ti plates to obtain the β-CD/MWCNT/Ti substrate. Binary Pd-Ni nanoparticles were electrodeposited on the surface of β-CD/MWCNT/Ti substrate to prepare the PdNi-β-CD/MWCN/Ti electrode; its activity in electrocatalytic oxidation of propanol and butanol isomers in alkaline media was then investigated by voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results indicated that the binary PdNi nanoparticles are highly dispersed with the size of 90~130 nm on the β-CD/MWCNT/Ti substrate. The configuration of alcohols plays a significant role in their electrochemical oxidation activity in alkaline media on the PdNi-β-CD/MWCNT/Ti electrode. For the two propanol isomers, the PdNi-β-CD/MWCNT/Ti electrode exhibits much higher electroactivity for 1-propanol oxidation than that for 2-propanol oxidation. For the four butanol isomers, the electrocatalytic activity of the PdNi-β-CD/MWCNT/Ti electrode towards their oxidation follows the order of 1-butanol > 2-methyl-propanol > 2-butanol >> 2-methyl-2-propanol; the electrode shows almost no electrocatalytic activity in the oxidation of tertiary butanol. The mechanism for the electrocatalytic oxidation of various propanol and butanol isomers was also analyzed by considering the Muliken net charge on the different carbon atoms bonded with hydroxyl –OH, which indicates that the alcohol molecule with lower Muliken net charge value will be more easily oxidized over the PdNi-β-CD/MWCNT/Ti electrode.