Effects of electrolyte variation on ammonia sensing temperature for BiVO4 sensing electrode in mixed potential gas sensor

Abstract

The aim of the present study is to investigate BiVO4 sensing electrode (SE) based electrochemical gas sensor for ammonia (NH3) sensing. Additionally, this study is also focused to reduce the operating temperature of sensor by applying different electrolytes i.e., yttria stabilized zirconia (YSZ) and gadolinia doped ceria (GDC). The maximum sensor response obtained for YSZ and GDC based cells towards 80 ppm NH3 were − 103.03 and − 78.81 mV at 600 ℃ and 550 ℃, respectively. Corresponding sensitivity of YSZ and GDC based cells for NH3 sensing were − 99.24 and − 42.66 mV/decade, respectively. Both the sensors demonstrate excellent selectivity as well as stability against 80 ppm NH3 (10 cycles) and humidity variation (pH2O = 0–0.12 atm.). Electrochemical impedance spectra (EIS) and dc polarization (I-V) curves confirms the mixed-potential sensing mechanism of the sensors. The systematic dependency of electrode’s resistance at a given frequency on the gas concentration reveals a novel pathway for prediction of sensors’ behavior. Additionally, the presence of GDC electrolyte decreases the response/recovery time (16/125 s) compared to YSZ-based cells (21/159 s) against 320 ppm NH3 at 550 ℃ which demonstrate its low temperature sensing capability. This 50 ℃ reduction in the operating temperature can be useful for extension of lifetime of sensor.