Ag modified metal oxides (MOx) as sensing electrodes for CeO2 based mixed potential hydrogen sensors

Trace detection and early warning of H2 leakage at high temperatures were of great significance for eliminating safety hazards and ensuring the safety of human lives and property. In this paper, Ce0.8Gd0.2O1.95 based mixed potential H2 sensor were constructed using Ag@MOx (MOx = TiO2, In2O3, ZnO, V2O5) as sensing electrodes synthesized by photochemical reduction method. Two sensing materials (Ag@TiO2 and Ag@In2O3) with excellent performance were selected by analyzing gas sensing properties of different sensing electrodes for H2. Specifically, the detection range of the sensor with Ag@TiO2 as the sensing electrode (operating temperature of 480 degrees C) was 1-10000 ppm, and the response to 200 ppm H2 was -67 mV. The detection range of the sensor with Ag@In2O3 (operating temperature of 490 degrees C) was up to the detection of 1-40000 ppm. The response value was -68 mV for 200 ppm H2. The interaction between Ag and the oxide (synergistic hydrogen spillover effect), and the electron transfer behavior at the interface of Ag and oxide caused by the difference of work function were the main reasons for the sensitivity of sensors to H2. This study contributed to an in-depth understanding for the influence of electronic behavior at the interface of noble metal and oxide on the sensing performance of solid electrolyte type gas sensor. Not only a new reference for subsequent researchers to construct high performance solid electrolyte type H2 sensors was provided, but also a new choice for accurate and stable detection of H2 over a wide concentration range at high temperatures was offered.