Development of a Nb-Doped TiO_2 Semiconductor pH Sensor for the Use in High-Temperature Aqueous Solutions

利用掺Bh的二氧化钛单晶研制了一种用于高温水溶液pH测量的半导体pH传感器。该传感器的pH响应是基于半导体电极的平带电位E&lt；Fb&gt；随pH的变化。E&lt；Fb&gt；的值可以通过测量半导体电极在溶液中的莫特-肖特基图来获得。在298-523K温度范围内，在不同组成和不同pH值的溶液中，对不同掺杂程度的Nb_2O_5掺杂的TiO_2单晶电极进行了曲线测量。结果表明，在所有实验条件下，用质量分数为0.01%的Nb_2O_5掺杂电极在10赫兹频率下测得的曲线具有良好的线性关系，E&lt；Fb&gt；与溶液pH‘s呈直线关系(-2.303RT/F)。该电极可用于523K以下纯水的pH测量。该传感器的pH响应快速、稳定，不受溶液中氧化还原体系的影响。然而，在较高的K~(++)和Na~(++)浓度下观察到了干扰效应。

A semiconductor pH sensor using a Bh-doped TiO_2 single crystal has been developed for pH measurement in high temperature aqueous solutions. The pH response of this sensor is based on the pH-dependent change in the flatband potential, E_<fb>, of semiconductor electrode. The value of E_<fb> can be obtained by measuring the Mott-Schottky plot on the semiconductor electrode in a solution. The measurement of the plots has been done on the Nb_2O_5-doped TiO_2 single crystal electrodes with different doping levels in solutions having various composition and pH's at temperatures in the range 298-523K. It was found that the plots measured using the 0.01mass% Nb_2O_5-doped electrode at a frequency of 10Hz had good linearity under all experimental conditions used and the relationships between the values of E_<fb> and the solution pH's showed straight lines with the Nernstian slopes (-2.303RT/F). The pH of pure water at temperatures up to 523K could be measured by this electrode. The pH response of the sensor was fast, stable and not affected by redox systems in the solutions. Interfering effects were observed, however, at higher K^+ and Na^+ concentrations.