Enhanced selective performance of mixed potential ammonia gas sensor by Au nanoparticles decorated CeVO4 sensing electrode

A mixed-potential type sensor using a new sensing electrode (SE) of CeVO 4 is developed for NH 3 detection. Well-dispersed Au nanoparticles are introduced into the CeVO 4 -SE by a simple immersion method to further improve the performances, especially the selectivity of the sensor. The sensor using the CeVO 4 -SE exhibits well response-recovery characteristics to NH 3 at 500–600 °C. Good linear correlations between the response potential difference of sensor and the logarithm of NH 3 concentrations are obtained. The sensor displays the negligible cross-sensitivities to CH 4 and CO 2 except NO 2 present in the gas mixture. After the introduction of the Au nanoparticles into the CeVO 4 -SE, the sensitivities of the sensor reach −78.9, −77.3 and −43.1 mV/decade at 500, 550 and 600 °C, respectively, which are much higher than those using the single CeVO 4 -SE. More importantly, the cross-sensitivity of the sensor with CeVO4/Au-SE to NO 2 is almost eliminated. Introduction of 1000 ppm NO 2 in sample gas containing 300 ppm NH 3 causes a response Δ V from 67.2 (for CeVO 4 -SE) to 4.6 mV (for CeVO 4 /Au-SE). The complex-impedance measurements display that introduction of Au can promote electrochemical oxidation reaction of NH 3 to TPBs. The results of the temperature-programmed desorption indicate that the improvement of the selectivity is attributed to the effective depression of NO 2 adsorption in the sensing electrode by introduction of Au.