“…Pure WO 3 can easily detect oxidizing gases such as NO 2 , SO 2 , O 3 , etc. [ 5 , 6 , 7 , 8 , 9 , 10 ], but more challenging is an enhancement of its sensitivity towards reducing gases (H 2 , CO, NH 3 , etc.). This can be done by the loading of WO 3 material by noble catalysts such as Au, Pt, and Pd [ 1 , 3 , 11 , 12 , 13 ].…”