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A series of NiO-WO 3 composite nanofibers with different molar ratios (Ni/W ¼ 0%, 1%, 3% and 5%) were fabricated based on an electrospinning and calcination technique. The gas sensing performances of sensors based on the as-produced nanofibers were studied towards acetone in detail. Compared with the pure WO 3 nanofibers, the porous NiO-WO 3 composite nanofibers exhibited higher sensitivity, faster response, and shorter recovery time towards acetone. Particularly, the 3 mol% NiO-WO 3 heterojunction nanofibers demonstrated the largest sensitivity, exhibiting a prominent value of 22.5 under 100 ppm acetone at the operating temperature of 375 C, which is almost 2.1 times larger than that of the pure WO 3 nanofibers. Moreover, the 3 mol% NiO-WO 3 heterojunction nanofibers also exhibited excellent selectivity and long-term stability to acetone. The combined effects including the formation of p-n heterojunctions between NiO and WO 3 , high oxygen species absorbing capacity, and special porous structural features with high surface area and small grain size, contributed to the enhanced sensing properties of the 3 mol% NiO-WO 3 composite nanofibers. These attractive gas sensing properties enable the NiO-WO 3 heterojunction nanofibers to be a promising material for application in gas sensors.

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