SO₂ Non-equilibrium Gas Sensor Based on Na₃Zr₂Si₂PO₁₂ Solid Electrolyte

This paper reported fabrication and sensing properties of solid-state gas electrochemical sensors for sulfur dioxide based on a non-equilibrium working mechanism. Based on Na₃Zr₂Si₂PO₁₂(NASICON) solid electrolyte, SO₂ non-equilibrium gas sensors were fabricated by using Na₂SO₄-BaSO₄ mixture and NaRe(SO₄)₂ as sensing electrodes. The results showed that there was a good linear relationship between the logarithm of SO₂ gas concentration and the sensor output electric potential value. Working at low temperature of 260℃, the sensors display best performances, with sensitivity up to 160 mV/decade and 136 mV/decade. Furthermore, the devices has good repeatability and stability. AC impedance of the sensors in different concentrations of SO₂ gas reveals that the electrochemical activity at three phase boundary (TPB) rised with the increased SO₂ concentration. Working temperature of the prepared sensor is obviously decreased which is benefited from the high Na⁺ conductivity of NASICON at low temperature. The sensor possesses good stability and repeatability due to its high chemical stability of Na₂SO₄-BaSO₄ mixture and NaRe(SO₄)₂ as sensing materials. The sensor based on non-equilibrium mechanism has many advantages, such as low-cost and simple structure. Owing to the above features, the sensor can be possibly applied in the environment monitoring of SO₂.