Smart pH Sensor Using Untreated Platinum Sheet Based on Chronopotentiometry and Long-Term Stability Analysis

In this paper, we design a smart pH sensor using untreated platinum sheet based on chronopotentiometry. This novel pH sensor is very suitable for applications in the deep sea, highly polluted water, and other harsh environments, where maintenance is difficult. In order to verify the long-term monitoring stability of the pH sensor, 17-day monitoring experiments are conducted in river water. We draw some conclusions for the properties of the pH sensor. First, the pH values obtained from the positive current agreed well with the pH glass electrode, indicating that it is suitable for pH monitoring. Moreover, the deviation derived from hysteresis is small. Second, the pH values obtained from the negative current could not reflect the actual pH of river water in long-term measurement. There may be two reasons for this: the changing conductivity in the river water and the unstable composition of the platinum sheet. Third, the conductivity may have an obvious impact on the potential obtained from the negative current; the electrochemical reaction where Pt is oxidized to PtO may be influenced by the ionic strength of the solution. Therefore, the pH values obtained from the positive current is more suitable for long-term pH monitoring.