Electrochemical Impedance Spectroscopic Analysis of RuO2 Based Thick Film pH Sensors

TiO2-Based Thick Film pH Sensor

“…In an impedancemetric and/or conductimetric based sensor, any changes that occur on the surface of the sensitive electrode while reacting with solution, changes the electrical properties of the sensor [2,14,23,31]. For a constant pH, we see decrease in the impedance and increase in phase as the frequency increases.…”

“…In the case of TiO 2 , the dissociative chemisorption of water molecule results in the formation of surface hydroxyl group [15]. Due to adsorption/diffusion of H + /OH -ions the surface of TiO 2 becomes charged and it creates an electrical double layer structure by site binding theory [23,32]. With changes in the pH of a solution the contribution of both H + and OH -ions also varies.…”

“…6. Observed behavior of the sensor from the Nyquist plot in analyzed frequency range, was discussed in more details in Section III.C, but a large incomplete arc in the Nyquist plot is possibly due to charge transfer and ion exchange at the surface of the material while reacting with ions in the solution [14,23,31].…”

“…The fabrication procedure of the conductimetric pH was similar to that reported in [2,23]. We chose alumina as a substrate to investigate the performance of pure metal oxide and to avoid any reaction at metal-metal oxide interface.…”

“…These changes in impedance and phase of TiO 2 based sensor can be attributed to electrochemical surface reaction of H + /OH -ions with the oxide surface. When a metal oxide is introduced into an electrolyte, many electrochemical reactions occur at the oxide-solution surface [2,23]. In the case of TiO 2 , the dissociative chemisorption of water molecule results in the formation of surface hydroxyl group [15].…”