纳米分子筛LTA包裹Ni-Salen配合物为修饰碳糊电极用于电催化氧化肼反应

采用柔性配体法将Ni-salen配合物包裹在纳米分子筛LTA的超笼中,用来修饰碳糊电极制得Ni(Ⅱ)-SalenA/CPE,并采用循环伏安法、计时电流法和计时库仑法考察了该电极电催化氧化0.1 mol/L NaOH溶液中肼反应性能.首先采用无有机模板剂法合成纳米分子筛LTA,并用各种技术进行了表征.XRD和粒径分析结果分别显示LTA晶体的平均粒径为56.1和72nm.在Ni(Ⅱ)-SalenA/CPE电极氧化还原位上水合肼催化氧化反应电子转移系数为0.64,速率常数为1.03×105cm3/(mol·s).电催化反应机理研究表明,水合肼氧化反应通过它与Ni3+(Salen)O(OH)反应或直接进行电氧化反应.阳极峰电流与扫描速率的平方根呈线性关系,表明反应受扩散控制,水合肼的扩散系数为1.18×10?7cm2/s.结果表明,Ni(Ⅱ)-SalenA/CPE对水合肼氧化反应表现出高的电催化活性,这是由于纳米分子筛LTA的多孔结构以及Ni(Ⅱ)-Salen的存在.最后研究了水合肼在碱性溶液中Ni(Ⅱ)-SalenA/CPE电极上的氧化反应机理,发现其为四电子过程,第一个电子转移反应为速率控制步骤,然后是一个三电子过程,产生环境友好的最终产物氮气和水.

Encapsulation of a nickel Salen complex in nanozeolite LTA as a carbon paste electrode modifier for electrocatalytic oxidation of hydrazine

A nickel salen complex was encapsulated in the supercages of nanozeolite NaA, LTA (linde type A) structure, using the flexible ligand method. The electrochemical behavior and electrocatalytic activ-ity of a carbon paste electrode (CPE) modified with Ni(Ⅱ)-Salen-A (Ni(Ⅱ)-SalenA/CPE) for hydrazine oxidation in 0.1 mol/L NaOH solution were investigated by cyclic voltammetry, chronoamperome-try, and chronocoulometry. First, organic-template-free synthesis of nanozeolite LTA was per-formed and the obtained material was characterized by various techniques. The average particle size of the LTA crystals was estimated to be 56.1 and 72 nm by X-ray diffraction and particle size analysis, respectively. The electron transfer coefficient was found to be 0.64 and the catalytic rate constant for oxidation of hydrazine at the redox sites of Ni(Ⅱ)-SalenA/CPE was found to be 1.03 × 105 cm3/(mol·s). Investigation of the electrocatalytic mechanism suggested that oxidation of hydra-zine occurred through reaction with Ni3+(Salen)O(OH) and also direct electrooxidation. The anodic peak currents revealed a linear dependence on the square root of the scan rate, indicating a diffu-sion-controlled process, and the diffusion coefficient of hydrazine was found to be 1.18 × 10–7 cm2/s. The results indicated that Ni(Ⅱ)-SalenA/CPE displays good electrocatalytic activity toward hydra-zine oxidation owing to the porous structure of nanozeolite LTA and the Ni(Ⅱ)-Salen complex. Fi-nally, the general reaction mechanism for the electrooxidation of hydrazine on Ni(Ⅱ)-SalenA/CPE in alkaline solution involves the transfer of four electrons, in which the first electron transfer reaction acts as the rate-limiting step followed by a three-electron process to generate environmentally friendly nitrogen and water as final products.