Functionalization of Lanthanated and Thoriated Tunsten Electrodes for pH Sensing

The aim of this study was to evaluate the electrochemical performance of functionalized lanthanated (WLa) and thoriated (WTh) tungsten electrodes as pH sensors, with a focus on their sensitivity, hysteresis, and response time. The goal was to determine the effect of La₂O₃ or ThO₂ combined with WO₃ on the performance of the electrodes for general pH-sensing applications. A simple and low-cost functionalization method based on an oxidant flame from an oxyacetylene torch was used to produce a combined oxide film on the tungsten electrode. The electrochemical response of both electrodes was compared in terms of key parameters. The WLa electrode demonstrated higher sensitivity (-58.8 mV pH^-1), a faster response time (18.4-19.4 s), and moderate hysteresis (12.1 mV), whereas the WTh electrode exhibited lower sensitivity (-41.6 mV pH^-1), a response time of 19.8-21.1 s, and lower hysteresis (8.6 mV). X-ray photoelectron spectroscopy (XPS) analysis was conducted to explore the oxygen vacancies in both electrodes and their impact on electrode performance. The WLa electrode, with more oxygen vacancies, displayed superior sensitivity and a faster response time, making it well suited for general pH sensing. In contrast, the WTh electrode, with fewer oxygen vacancies, exhibited lower sensitivity but reduced hysteresis, which could be advantageous in applications where hysteresis is a critical factor. Both electrodes are durable and cost-effective alternatives to traditional sensing methods, offering high adaptability and reliability.