A Potentiometric $\hbox {CO}_{2}$ Sensor Combined With Composite Metal Oxide and DOP Plasticizer Operative at Low Temperature

A low-temperature lithium ion based potentiometric CO₂ sensor has been developed by adding 10 mol% of SiO₂, B₂O₃, Li₂O, and Bi₂O₃ composite metal oxide mixture to (Li₂-Ba)CO₃ sensing bicarbonate. The sensors added with different mol% of oxides were tested at different operating temperatures. The sensor with 1:2:1:1 mol% of the SiO₂:B₂O₃:Li₂O:Bi₂O₃ composite metal oxide showed a fair Nernstian correlation and obtained n value equal to 2 at 300degC, where n is the number of reaction electrons. A glassy sensing phase resulted that improved response and recovery. The sensor is also found stable against humidity (70% RH) at 300 degC. However, it is further observed that the performance of the sensor deteriorated with increasing Li₂O or decreasing B₂O₃ content. The sensor performance could further be improved at lower temperatures with the introduction of dioctyl phthalate (DOP) plasticizer into the sensing electrode.