Room temperature H₂S gas sensing characteristics of platinum (Pt) coated porous alumina (PoAl) thick films

The study reports H₂S gas sensing characteristics of platinum (Pt) coated porous alumina (PoAl) films. The porous alumina (PoAl) thick layers were formed in the dark on aluminum substrates using an electrochemical anodization method. Thin semitransparent platinum (Pt) films were deposited on PoAl samples using chemical bath deposition (CBD) method. The films were characterized using energy dispersive X-ray analysis (EDAX) and scanning electron microscopy (SEM). The thicknesses of coated and bare films were measured using ellipsometry. The sensing properties such as sensitivity factor (S.F.), response time, recovery time and repeatability were measured using a static gas sensing system for H₂S gas. The EDAX studies confirmed the purity of Pt–PoAl film and indicated the formation of pure platinum (Pt) phase. The ellipsometry studies revealed the thickness of PoAl layer of about 15–17 μm on aluminum substrates. The SEM studies demonstrated uniform distribution of spherical pores with a size between 0.250 and 0.500 μm for PoAl film and nearly spherical platinum particles with average particle size ∼100 nm for Pt–PoAl film. The gas-sensing properties of these samples were studied in a home-built static gas characterization system. The H₂S gas sensing properties of Pt–PoAl at 1000 ppm of H₂S gave maximum sensitivity factor (S.F.) = 1200. The response time and recovery time were found to be 2–3 min and ∼1 min respectively. Further, the measurement of H₂S gas sensing properties clearly indicated the repeatability of gas sensing response of Pt–PoAl film. The present study indicated the significant potential of Pt coated PoAl films for H₂S gas sensing applications in diverse areas. - Highlights: • Electrochemical anodization, cheap and effective method for fabrication of PoAl. • Chemical bath deposition, a simple and effective method for deposition of Pt on PoAl. • A nano-composite film sensor with high sensitivity (S.F. = 1200). • The study indicates significant potential of Pt–PoAl film for H₂S gas sensing