In Situ pH Monitoring in Turbid Coastal Waters Based on Self-Electrodeposition Ir/IrO2 Electrode

Abstract

Direct and accurate monitoring of pH in turbid waters is a challenging task for environmental monitoring and analysis. In this study, iridium oxide (IrO2) with selective sensing ability toward H+ was produced on the surface of iridium (Ir) electrode by rapid self-electrodeposition. IrO2 was deposited on electrode surface by atomic force, which could decrease the adverse effect of the suspended particles in turbid water. Properties of the Ir/IrO2 electrode were investigated by X-ray photoelectron spectroscopy, scanning electron microscopy, and electrochemical technology. The sensitivity and response time of the Ir/IrO2 electrode for pH determination were assessed, and a rapid and linear pH response of approximately 65 ± 3.5 mV pH−1 was observed across a wide pH range between 1.8 and 11.9. Moreover, the electrode exhibited a good temperature linearity (20 °C–60 °C), low potential drift (0.75 mV h−1), high accuracy (±0.05), and a long life span (up to 30 d). The practical investigation revealed faster equilibrium rate and higher stability of the Ir/IrO2 electrode than that of traditional glass pH electrode. Furthermore, the Ir/IrO2 electrode was successfully used for in situ pH monitoring in 750 formazin turbidity units (FTU) for turbid coastal river water. Therefore, the developed Ir/IrO2 pH electrode offers large applicability for in situ pH monitoring in turbid environmental water matrices.