PH-sensing properties of PbO2 thin film electrodeposited on carbon ceramic electrode

Abstract

In this paper, a new highly sensitive potentiometric pH electrode is proposed based on the solid-state PbO2 film electrodeposited on carbon ceramic electrode (CCE). Two different crystal structures of PbO2, α and β were examined and the similar results were obtained. Moreover, the experimental results obtained for the proposed pH sensor and a conventional glass pH electrode were in good agreement. The electromotive force (emf) signal between the pH-sensitive PbO2-coated CCE and SCE reference electrode was linear over the pH range of 1.5–12.5. Near-Nernstian slopes of −64.82 and −57.85 mV/pH unit were obtained for α- and β-PbO2 electrodes, respectively. The interferences of some mono-valence and multi-valence ions on potentiometric response of the sensor were studied. The proposed pH sensor displayed high ion selectivity with respect to K+, Na+, Ca2+, and Li+, with log $$K_{H,M}^{{\text{pot}}} $$ values around −12 and has a working lifetime of about 30 days. Key parameters important for the pH sensor performance, including kind of PbO2 film, selectivity, response time, stability, and reproducibility, have been characterized. The proposed electrode showed a good efficiency for direct pH-metry after calibration and pH-metric titrations without calibration step. The response time was about 1 s in acidic medium and less than 30 s in alkaline solutions. The pH values of complex matrix samples such as fruit juices measured by the proposed sensor and a conventional glass pH electrode were in good agreement.