Effects of CeVO_4 electrode morphology and oxygen content on ammonia sensing properties for potentiometric sensor

摘要

The influences of sensing electrode morphology, operating temperature and the oxygen content on NH3 sensing properties for the potentiometric gas sensor attached with CeVO4 sensing electrode were studied. With the increase of electrode sintering temperature, CeVO4 grains grow up gradually. The response/recovery time shows a decreasing trend, but the NH3 sensitivity reaches the highest when the sintering temperature reaches 1000 degrees C, this was determined by the amount of TPB and the ammonia concentration involved in the electrode electrochemical reactions. The NH3 sensitivity enhances with the increase of operating temperature in the range of 450-550 degrees C and presents the mixed-potential characteristic. When the temperature exceeds 600 degrees C, the curve between Delta V and logarithm of NH3 concentration presents a broken line relationship, and the concentration corresponding to the inflection point increases with the increase of operating temperature. The response and recovery rates accelerate but the NH3 sensitivity decreases with the increase of oxygen content in testing gas. When the oxygen is above 10 vol.% and NH3 is below 80 ppm, the response value is almost unaffected by the change of oxygen concentration. The broken line feature of the sensitivity curve under high operating temperatures and oxygen concentrations is mainly related to the gas phase catalytic reaction of NH3 by oxygen.