Simple Solid-state Ag/AgCl Reference Electrode and Its Integration with Conducting Polypyrrole Electrode for the Production of All-solid-state pH Sensor

Abstract

In this work, a solid-state Ag/AgCl electrode was successfully fabricated via electrodeposition of silver, followed by chlorination in the presence of ferric chloride to obtain silver chloride. Stainless steel rod was used as the supporting electrode. XPS and SEM were performed on the surfaces of silver to investigate the changes in surface composition and morphology, revealing the successful formation of silver chloride on the silver layer after the chlorination process. Calibrated against the commercial Ag/AgCl electrode, the developed solid-state Ag/AgCl electrode showed insensitive potentiometric response in different buffer solutions with the response time of 10 s. All-solid-state pH sensor, constructed by integrating the solid-state Ag/AgCl electrode with the polypyrrole-based pH indicative electrode, showed a linear potentiometric sensitivity of –53.55±1.33 mV.pH^-1 (r² > 0.99) over pH range of 2–12 with excellent reproducibility. The pH measurement in the selected real solutions was demonstrated, suggesting that the constructed all-solid-state pH sensor showed the comparable sensing performance to the commercial glass pH electrode. The all-solid-state sensor is currently miniaturized for the further use in microfluidics and flow injection analysis system.