Innovative experiments and teaching practices in exploring the gas-sensitive properties of tin dioxide materials

Metal oxide semiconductor gas-sensing materials, such as tin dioxide (SnO₂), suffer from poor selectivity, long-term instability, and difficulty achieving accurate monitoring in complex environments (e.g., varying humidity and interfering gases). Reliable detection of methane (CH₄), a major greenhouse gas and explosion hazard in coal mines and industrial settings, is required. However, pristine SnO₂ sensors often exhibit cross-sensitivity to other reducing gases and gradually degrade due to poisoning by sulfides or water vapor. Meanwhile, traditional experimental education emphasizes procedural compliance over innovation, making it difficult to cultivate compound safety experts who can integrate materials science, sensor engineering, and data analysis. In response to the nation’s urgent need for energy safety and environmental monitoring, this study focuses on using SnO₂-based gas sensors to detect methane, aiming to explore ways to optimize their performance through anti-poisoning modifications. Furthermore, the research outcomes are transformed into teaching content to enhance students’ practical skills and innovative thinking.

The experimental research encompasses material synthesis, modification with 1 wt% Pt, 1 wt% Pd, and different CeO₂ mass fractions (0–20 wt%), systematic testing of sensor response (CH₄ concentrations of 325–6500 mg/m₃), long-term stability over 15 days, and anti-poisoning performance in a mixed atmosphere of 325 mg/m³ CH₄ and 66.4 mg/m³ hexamethyldisiloxane (HMDSO). On this basis, an innovative “research-driven, problem-oriented” experimental teaching model is constructed. The model focuses on optimizing the performance of SnO₂-based methane sensors, enabling students to systematically master key procedures, including the preparation of gas-sensing materials, sensor assembly, operation of gas-sensing and characterization equipment (e.g., tube furnaces, scanning electron microscopy (SEM), and X-ray diffraction (XRD)), and data acquisition and analysis. The pedagogical model comprises five fundamental components: (1) Research thinking training: Guided by national energy safety needs, students progress through three dimensions (sensing response → mechanism analysis → device optimization) to build a systematic research framework. (2) Innovation ability stimulation: Students independently design experimental schemes to explore performance enhancement pathways. (3) Teamwork cultivation: Group-based collaboration encompasses material synthesis, device fabrication, and performance testing. (4) Scientific attitude development: Students conduct multiple rounds of testing and data fitting using Origin software. (5) Theory and practice integration: Students apply their knowledge of semiconductor physics and surface chemistry to real problems, such as coal mine gas warning and urban gas leak detection.

Pristine SnO₂ exhibits a response value of only 2.11 to 6500 mg/m₃ CH₄ at 5 V, with response/recovery times of 13 s/67 s. Following impregnation with 1 wt% Pt and 1 wt% Pd, the response increases to 3.846 (82.2% improvement), and response/recovery times shorten to 10 s/22 s (23.07% and 67.16% reductions, respectively). The optimal operating temperature for doped samples is 300–360 ℃. The 20% CeO₃ sample demonstrated the optimal overall performance, exhibiting a robust response even at 325 mg/m³ CH₄. Long-term stability tests lasting 15 days on the optimal sensor (20% CeO₂+Pt + Pd) indicate a final stable response of 11.476±0.719. Anti-poisoning tests in a CH₄/HMDSO mixed atmosphere have demonstrated that a higher content of CeO₂ significantly suppresses siloxane-induced sensitivity degradation. In the educational setting, the implementation of this innovative teaching model yields significant advantages. Students gain hands-on experience with advanced equipment (SEM, XRD, gas-sensing test platforms), and their ability to formulate hypotheses, design experiments, and analyze data is markedly improved. Furthermore, teamwork and scientific rigor (e.g., data fitting with Origin) are enhanced, and theoretical knowledge is successfully applied to practical scenarios. Surveys administered post-course indicate that a minimum of 90% of students report an enhancement in their research literacy and engineering skills.

This work effectively enhances the methane sensing performance, long-term stability, and anti-poisoning capability of SnO₂ through the process of co-doping with Pt, Pd, and CeO₂. It establishes an innovative “research-driven, problem-oriented” experimental teaching model that systematically cultivates students’ research thinking, innovation ability, teamwork, scientific attitude, and theory-practice integration. The integrated approach addressed the key technical challenges associated with SnO₂ sensors, establishing a replicable paradigm for functional materials research and experimental teaching reform in academic institutions.