金属配合物在ATO/SiO₂大孔电极上的电催化氧化

Electrooxidation of Metal Complexes on ATO/SiO₂Macroporous Electrodes

摘要: 通过SnCl2和SbCl3前驱物的两步水解和高温烧结方法将原位生成的纳米Sb-SnO2(Antimony-doped tin oxide，ATO)均匀负载到SiO2大孔材料上，制备出具有三维复合结构的大孔电极。用SEM、HRTEM和XRD等对该新材料进行结构表征，并测定了材料的比表面积与导电性。用该电极作为阳极开展了铁、铜、镍三种可溶性金属配合物的电催化氧化研究，用XPS鉴定氧化后的固体产物分别是水合氧化铁、氧化镍和单质铜，溶液中金属离子浓度则用原子吸收方法测定，再通过COD测定来跟踪配体化合物的单独氧化过程，这些金属配合物的电氧化实验结果证明：其中的有机配体如CN–、SCN–和EDTA转变成低毒害物质而加以清除，90%以上的金属离子可转变成铁、镍的氧化物或金属铜加以回收。进一步的研究发现SCN–在大孔电极内部发生脱硫反应，所生成的硫在纳米ATO表面的极化作用诱导下发生歧化反应，生成S^2- 和 SO₄^2- 。

Abstract: Large-sized and macroporous SiO₂ was used as a new support in which SnCl2 and SbCl3 were introduced in solution state and then converted into nano-sized Sb-SnO₂ (ATO) through two-step hydrolysis and subsequent calcination at high temperature. The structures of the new materials were characterized by SEM, HRTEM and XRD, and the properties such as specific surface area and conductivity were also measured. The new materials have been served as macroporous anodes to study the electro-catalytic oxidation of complexes containing metal ions such as Fe, Cu and Ni. The solid products from the oxidation of the Fe complexes and Ni complexes were identified by XPS to be Fe₂O₃xH₂O and NiO, respectively, while the product from Cu complexes was elementary copper. The measurement of the content of metal in solution by means of atom absorption indicated that above 90% of metal can be recycled from the solution of the corresponding complex. Through measuring the COD of pure ligands during oxidation it was found that CN–, SCN– and EDTA can be degraded to produce less harmful substances, the final COD reached to a very low level. Further-step investigations indicated that SCN– can be desulfurized in the macroporous anode to produce CN– and sulfur. Since both of S^2- and SO₄^2- were found in the mixture of the products, it might be implied that a disproportionation reaction of the resulted sulfur had been induced on the surface of nano-ATO probably by strong effect of polarization.