Bimodally Porous WO₃ Microbelts Functionalized with Pt Catalysts for Selective H₂S Sensors

Bimodally meso- (2-50 nm) and macroporous (>50 nm) WO₃ 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 WO₃ 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 WO₃ MBs, dominated by Knudsen diffusion. The macropores further accelerate gas permeability in the interior and on the exterior of the WO₃ 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 WO₃ MBs functionalized by Pt catalysts showed remarkably high hydrogen sulfide (H₂S) response ( R_air/ R_gas = 61 @ 1 ppm) and superior selectivity to H₂S against other interfering gases, such as acetone (CH₃COCH₃), ethanol (C₂H₅OH), ammonia (NH₃), and carbon monoxide (CO). These results demonstrate a high potential for the feasibility of catalyst-loaded meso- and macroporous WO₃ MBs as new sensing platforms for the possibility of real-time diagnosis of halitosis.