Noble Metal/Tin Dioxide Hierarchical Hollow Spheres for Low-Concentration Breath Methane Sensing

Abstract

The high surface area, penetrable shell, and loaded catalyst are of crucial importance to sensing performance of semiconductor oxide sensors by providing sufficient active sites, good diffusion path, and catalytic effect. Here, we report a novel general synthetic protocol to noble metal/SnO2 (M/SnO2) hierarchical hollow spheres (HHSs) through one-pot in situ polymerization and calcination. In particular, the Pt/SnO2 HHSs have a mean diameter of ∼0.5 μm, uniform distribution of PtO and PtO2 nanoparticles in the shell, high surface area of greater than 90 m2/g, and pore size of 3∼8 nm. Interestingly, the Pt/SnO2 HHSs exhibit improved CH4 sensing response (4.33–250 ppm, 20% relative humidity (RH)) compared to Pt/SnO2 HSSs (1.82) and pristine SnO2 HHSs (1.30). In addition, the low detection limit in high humid condition (20 ppm, 80% RH) and long-term stability also show excellent CH4 sensing characteristic, which might be applicable to the breath methane sensing for the constipation. Moreover, this method can also be applicable for Pd/SnO2 HHSs and Au/SnO2 HHSs, which would serve as a novel strategy in preparing various M/MOx HHSs with potential applications in disease diagnosis and gas alarm.