Pt-Pd Nanoalloys Functionalized Mesoporous SnO₂ Spheres: Tailored Synthesis, Sensing Mechanism, and Device...

Methane (CH₄ ), as the vital energy resource and industrial chemicals, is highly flammable and explosive for concentrations above the explosive limit, triggering potential risks to personal and production safety. Therefore, exploiting smart gas sensors for real-time monitoring of CH₄ becomes extremely important. Herein, the Pt-Pd nanoalloy functionalized mesoporous SnO₂ microspheres (Pt-Pd/SnO₂ ) were synthesized, which show uniform diameter (≈500 nm), high surface area (40.9-56.5 m² g^-1 ), and large mesopore size (8.8-15.8 nm). The highly dispersed Pt-Pd nanoalloys are confined in the mesopores of SnO₂ , causing the generation ofoxygen defects and increasing the carrier concentration of sensitive materials. The representative Pt₁ -Pd₄ /SnO₂ exhibits superior CH₄ sensing performance with ultrahigh response (R_a /R_g = 21.33 to 3000 ppm), fast response/recovery speed (4/9 s), as well as outstanding stability. Spectroscopic analyses imply that such an excellent CH₄ sensing process involves the fast conversion of CH₄ into formic acid and CO intermediates, and finally into CO₂ . Density functional theory (DFT) calculations reveal that the attractive covalent bonding interaction and rapid electron transfer between the Pt-Pd nanoalloys and SnO₂ support, dramatically promote the orbital hybridization of Pd₄ sites and adsorbed CH₄ molecules, enhancing the catalytic activation of CH₄ over the sensing layer.