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

研制了一种以掺氢TiO_2单晶为材料的半导体pH传感器，用于高温水溶液的pH测量。该传感器的pH响应基于半导体电极的平带电位E_<fb>的pH依赖性变化。E_<fb>可以通过测量溶液中半导体电极上的Mott-Schottky图得到。在298 ~ 523k的温度范围内，对不同掺杂水平的nb_2o_5掺杂TiO_2单晶电极在不同组成和pH的溶液中进行了测量。结果表明，在10Hz频率下，0.01质量% nb_2o_5掺杂电极测得的曲线在所有实验条件下都具有良好的线性关系，E_<fb>值与溶液pH的关系与Nernstian斜率（-2.303RT/F）呈直线关系。该电极可以测量温度高达523K的纯水的pH值。该传感器的pH响应快速、稳定，不受溶液中氧化还原系统的影响。然而，在较高的K^+和Na^+浓度下，观察到干扰效应。

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.