Twofold Porosity and Surface Functionalization Effect on Pt–Porous GaN for High-Performance H₂‑Gas Sensors at Room Temperature

The achievement of H₂ detection, up to 25 ppm, at room temperature using sulfur-treated, platinum (Pt)-decorated porous GaN is reported in this study. This achievement is attributed to the large lateral pore size, Pt catalyst, and surface treatment using organic sulfide. The performance of H₂-gas sensors is studied as a function of the operating temperature by providing an adsorption activation energy of 22 meV at 30 ppm H₂, confirming the higher sensitivity of the sulfide-treated Pt–porous GaN sensor. Furthermore, the sensing response of the sulfide-treated Pt–porous GaN gas sensor increases with the increase in porosity (surface-to-volume ratio) and pore radii. Using the Knudsen diffusion–surface reaction equation, the H₂ gas concentration profile is simulated and fitted within the porous GaN layer, revealing that H₂ diffusion is limited by small pore radii because of its low diffusion rate. The simulated gas sensor responses to H₂ versus the pore diameter show the same trend as observed for the experimental data. The sulfide-treated Pt–porous GaN sensor achieves ultrasensitive H₂ detection at room temperature for 125 nm pore radii.