Bimodally Porous WO 3 Microbelts Functionalized with Pt Catalysts for Selective H 2 S Sensors

Bimodally meso- (2–50 nm) and macroporous (>50 nm) WO 3 microbelts (MBs) functionalized with sub-3 nm Pt catalysts were fabricated via the electrospinning technique followed by subsequent calcination. Importantly, apoferritin (Apo), tea saponin and polystyrene colloid spheres (750 nm) dispersed in an electrospinning solution acted as forming agents for producing meso- and macropores on WO 3 MBs during calcination. Particularly, mesopores provide not only numerous reaction sites for effective chemical reactions, but also facilitate gas diffusion into the interior of the WO 3 MBs, dominated by Knudsen diffusion. The macropores further accelerate gas permeability in the interior and on the exterior of the WO 3 MBs. In addition, Pt nanoparticles with mean diameters of 2.27 nm were synthesized by using biological protein cages, such as Apo, to further enhance the gas sensing performance. Bimodally porous WO 3 MBs functionalized by Pt catalysts showed remarkably high hydrogen sulfide (H 2 S) response ( R air / R gas = 61 @ 1 ppm) and superior selectivity to H 2 S against other interfering gases, such as acetone (CH 3 COCH 3 ), ethanol (C 2 H 5 OH), ammonia (NH 3 ), and carbon monoxide (CO). These results demonstrate a high potential for the feasibility of catalyst-loaded meso- and macroporous WO 3 MBs as new sensing platforms for the possibility of real-time diagnosis of halitosis.