Visible Light Activation in TiO 2 /Pd/N/Fe 2 O 3 Nanofiber Hydrogen Sensor

In this paper, a Pd–TiO 2 nanofiber structure with photoactivation capability for H 2 gas sensing is made using the electrospinning procedure. The solution which was stacked into the syringe for electrospinning Pd–TiO 2 nanofibers consisted of titanium tetraisopropoxide, acetic acid, ethanol, polyvinyl pyrrolidone, and different amounts of Pd solution. The X-ray diffraction, field emission scanning microscopy, transmission electron microscopy, and spectrophotometry techniques were employed to analyze the crystalline structure and surface morphology of the nanofibers. Moreover, Fe 2 O 3 and HNO 3 were also used as additional additives and the effect of additives in the absorption spectrum shift towards the visible light spectrum was investigated. About 95-nm red shift toward visible light from 370 to 465 nm for TiO 2 /Pd/N/Fe 2 O 3 was observed in comparison with the pure TiO 2 nanofibers. By using additives and visible light irradiation, the operating temperature lowered from 290 °C to 130 °C and the response increased from 11 to 368. At an operating temperature of 150 °C, the response time also reduced from 25 to 0.9 s and recovery times reduced from 40 to 2 s. The response dropped only by $\sim 30$ %, 12%, and 5% after nine months for the TiO 2 , TiO 2 /Pd, and TiO 2 /Pd/N/Fe 2 O 3 samples, respectively.