A La10Si5.5Al0.5O27-δ based mixed-potential H2 sensor using Au-CeO2 composite sensing electrode

Abstract

Herein, a high-temperature applicable hydrogen sensor was prepared using a highly catalytically active Au-CeO₂ composite as a sensing electrode loaded on La₁₀Si_5.5Al_0.5O_27-δ electrolyte (LSAO). The CeO₂ addition hinders the sintering of Au and leads to forming the porous three-dimensional structure of the sensing electrode. Moreover, CeO₂ oxygen ion conduction enlarges the electrode reaction active sites, which improves the response performance of the sensor. Among all sensors, the sensor based on Au-40 wt% CeO₂ sensing electrode exhibits the largest response value and the highest sensitivity (-86.20 mV/decade) in 50–2000 ppm H₂ at 450°C. The Pt reference electrode covered by porous LSAO coating enhances the sensor sensitivity and shortens response and recovery time. When 50 ppm NO, 50 ppm NO₂, 1000 ppm CO or 2000 ppm CH₄, was introduced to test gas containing 500 ppm H₂, the response value change rate is + 0.35 %, −1.34 %, + 0.04 % and −0.61 %, respectively, showing that the sensor has excellent anti-interference for those interfering gases. The humidity and CO₂ have a greater effect on the sensor response, and 40 % humidity or 24 % CO₂ coexisting with 500 ppm H₂ causes the response decreases by −19.25 % or −8.89 %. However, it should be noticed that the sensor response signal has a little change over a wide concentration range of humidity or CO₂ (3–40 vol% humidity or 3–24 % CO₂). In addition, the sensor also shows good stability and reproducibility. The mixed potential mechanism of the sensor is verified using Tafel and polarization methods.