Synthesis of Pd-loaded mesoporous SnO₂ hollow spheres for highly sensitive and stable methane gas sensors

High performance methane gas sensors have become more and more essential in different fields such as coal mining, kitchens and industrial production, which necessitates the design and synthesis of highly sensitive materials. Herein, mesoporous SnO₂ hollow spheres with high surface area (>90 m² g^-1) are prepared by a progressive inward crystallization routine, showing a high response of 1.31 to 250 ppm CH₄ at a working temperature of 400 °C. Furthermore, loading noble metal Pd onto the surface of SnO₂ hollow spheres by an adsorption-calcination process improves the response to 4.88 (250 ppm CH₄) at the optimal dosage of 1 wt% Pd. Meanwhile, the working temperature decreases to 300 °C, showing the prominent spillover effect of catalytic Pd and PdO-SnO₂ heterostructure sensitization as evidenced by the binding energy shift in the X-ray photoelectron spectroscopy (XPS) analysis. The response/recovery time is as short as 3/7 s and the sensitivity is stable for a test period as long as 15 weeks. All these performances show the promise of the highly porous Pd-loaded SnO₂ hollow spheres for high performance methane sensors.