Abstract:

Electrolyzed oxidizing water (EOW), as an innovative disinfectant characterized by its high efficiency, broad antimicrobial spectrum, and non-toxic residues, has been broadly used in health care industry, medicines, agriculture, and food processing. EOW is usually generated by electrolysis of a dilute NaCl solution in a chamber with two cells separated by membrane, and is obtained from the anode side. But low current efficiency and short service life of the anode in EOW generators restrict the application of EOW. Ir_0.5Pt0_.5O₂ anode was prepared by the improved Adams fusion method. The properties of Ir_0.5Pt_0.5O₂ anode was investigated with X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemistry cyclic voltammetry (CV). The crystal type is rutile with (101), (002) and (301) crystal planes. A large number of cellular structures were observed on the surface of the anode, which greatly increased specific surface area of the anode. With increasing specific surface area, electric charge was enhanced to 0.4 mC, which was 2.65 times of pure IrO₂. Electrochemical characteristics of the anode surface, such as oxidation peaks at 1.0 V(Pt-OH) and 0.9 V(Ir³⁺/Ir⁴⁺) proved the formation of platinum iridium oxide. The activities of chlorine evolution and oxygen evolution were also studied through linear sweep voltammetry (LSV). Compared with IrO₂, chlorine evolution activity in unit apparent surface area increased significantly, but oxygen evolution activity decreased obviously. The slope of Tafel was 56.3 mV·dec^1- for chlorine evolution reaction (CER), and the mechanism was Volmer-Heyrovsky in which the rate controlling step was electrochemical desorption. The slope of Tafel was 126.6 mV·dec^1- for oxygen evolution reaction (OER), and the rate controlling step was formation of surface hydroxide on the catalyst surface. Electrochemical surface structure and electrochemical performance of Ir_0.5Pt_0.5O₂ oxide coatings in 1 g·L^-1 NaCl solution were investigated with electrochemical impedance spectroscopy (EIS). CER activity of Ir_0.5Pt_0.5O₂ was better than IrO₂, which was in agreement with previous research. In the actual EOW preparation, electrolysis efficiency and available chlorine content (ACC) of EOW on the Ir_0.5Pt_0.5O₂ anode were much greater than IrO₂ anode under the same condition. The accelerated life of Ir_0.5Pt_0.5O₂ anode was 3.14 times of the IrO₂ anode and the performance of the anode was greatly improved, which favored its commercial use.

Key words: Ir_0.5Pt_0.5O₂ composites, electrolysis, chlorine evolution, oxygen evolution, reaction kinetics

摘要：

氧化电解水作为一种新型、高效、环保的杀菌剂,具有广阔的应用前景。但目前在氧化电解水制备过程中,其阳极电催化材料存在效率低和使用寿命短等问题。采用亚当斯融合法制备了Ir_0.5Pt_0.5O₂复合氧化物电极。通过XRD表征,其晶型为典型的金红石型结构。SEM结果表明虽然颗粒之间存在团聚现象,但是可以明显观察到大量蜂窝状结构存在,提高了催化剂的比表面积和电化学面积。进一步的CV表征证明了这一点,同时在CV图中表现出明显的铂铱复合氧化物结构的特征。利用LSV技术分别考察了Ir_0.5Pt_0.5O₂的析氯和析氧极化曲线,发现其单位表观面积上析氯活性明显提高,而析氧活性明显降低。计算表明Ir_0.5Pt_0.5O₂的析氯反应Tafel斜率为56.3 mV·dec^-1,反应机理为Volmer-Heyrovsky机理,速控步骤为电化学脱附步骤;其析氧反应Tafel斜率为126.6 mV·dec^-1,控速步骤为催化剂表面氢氧化物的形成。进一步电化学阻抗实验表明在1 g·L^-1 NaCl溶液中, Ir_0.5Pt_0.5O₂析氯电催化活性优于IrO₂,这与前面研究结果一致。在此基础上,以Ir_0.5Pt_0.5O₂/Ti为阳极制备氧化电解水,在相同条件下,其有效氯含量明显优于IrO₂/Ti,同时电解效率也明显提高,强化试验寿命是IrO₂/Ti的3.14倍,大大提高了电极性能,有利于其商品化使用。

关键词: Ir_0.5Pt_0.5O₂复合材料, 电解, 析氯, 析氧, 反应动力学