Ti基IrO_2+Ta_2O_5阳极在H_2SO_4溶液中的电解时效行为

Aging Performances of Ti Based IrO_2+Ta_2O_5 Anodes in Sulfuric Acid During Electrolysis

研究了450℃制备所得Ti/70%IrO2-30%Ta2O5(摩尔分数)高寿命阳极在H2SO4溶液电解过程中电极的物理、化学及电化学性能的时效行为.结果发现,整个电解过程可分为“活化”、“稳定”及“失效”三个阶段.在“活化”及“稳定”区内主要发生电极表面活性氧化物的溶解,涂层中IrO2金红石相的(110)、(101)晶面择优取向随电解时间延长而减弱,而(002)晶面择优增强.但是在“失效区”内,各晶面的择优程度却不随电解时间的变化而变化,这表明在“失效区”内氧化物的损失机制发生了变化.电化学阻抗谱测试表明,电极的析氧电化学反应电阻随电解时间的延长发生缓慢而连续的上升,而整个电极的物理阻抗在“失效区”内却发生突升现象.X射线衍射分析(XRD)表明,随电解时间的延长TiO2金红石相的衍射强度增大,达“失效区”时衍射强度发生突升.根据实验现象特别是“失效区”内阳极的时效行为提出高寿命Ti基氧化物涂层阳极的失效机制.

Physico-chemical and electrochemical performances of long service life Ti/70% IrO2-30% Ta2O5 (mole fraction) anodes prepared at 450 degreesC have been investigated over the whole electrolysis time in H2SO4 solution. The results showed that the whole electrolysis process of this anode could be divided into three Stages consisting of 'active', 'stable' and 'de-active' ones. In the first two stages, the dissolution of coated oxides was dominated (with preferential loss of IrO2 component). It was found that, in these two stages, the preferential orientations of (110) and (101) planes in IrO2 rutile decreased with the electrolysis time, and that of (002) plane increased, while the preferential orientations remained to be stabilized in the 'de-active' region. This indicated that the loss mechanism of the catalyst coatings was changed. Electrochemical impedance spectroscopy (EIS) measurements showed a slight increase in oxygen evolution reaction resistance of the oxide catalysts while a sharp rise in totally physical impedance of the whole anode in the 'de-active' region. X-ray diffraction analysis (XRD) showed that the intensity of TiO2 rutile reflections increased with the electrolysis time, with a sharp increasing in 4 de-active' region. According to the experimental results the degradation mechanism for long service life Ti based coating anodes has been proposed.