YSZ-Based Mixed Potential Type Sensors Utilizing Pd-doped SrFeO ₃ Perovskite Sensing Electrode to Monitor Sulfur Dioxide Emission

Abstract

Sulfur dioxide (SO 2 ) is one of the key pollutants in the atmosphere that should be monitored in many combustion facilities. In this paper, YSZ-based mixed potential SO 2 sensors were developed utilizing the perovskite-type SrFeO 3 sensing electrode, and Pd doping was applied to enhance the sensing performance. It was found that the sensor utilizing the Pd 0.05 -SrFeO 3 sensing electrode showed the highest sensitivity toward 1–30 ppm SO 2 at 575 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>°</mml:mo> <mml:mi mathvariant="normal">C</mml:mi> <mml:mo>,</mml:mo> </mml:math> and exhibited a piecewise linear relationship between <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:mi>V</mml:mi> </mml:math> and the logarithm of SO 2 concentrations in this concentration range. The significant enhancement of sensing performances by 5 at% Pd doping was mainly attributed to the increasing of electrochemical catalytic activity of the anodic reaction. After the sensing performance test in the temperature range between 525 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>°</mml:mo> <mml:mi mathvariant="normal">C</mml:mi> </mml:math> –625 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>°</mml:mo> <mml:mi mathvariant="normal">C</mml:mi> <mml:mo>,</mml:mo> </mml:math> 575 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>°</mml:mo> <mml:mi mathvariant="normal">C</mml:mi> </mml:math> was selected as the optimum operating temperature. The sensing performances of the developed Pd 0.05 -SrFeO 3 sensor were further evaluated at 575 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>°</mml:mo> <mml:mi mathvariant="normal">C</mml:mi> <mml:mo>,</mml:mo> </mml:math> exhibiting good selectivity to CO, CO 2 , NO, and NO 2 interference and good long-term stability. In addition, the fluctuation of oxygen concentration can be corrected by the Butler-Volmer equation following the mixed potential theory.