Coaxial electrospinning of WO3 nanotubes functionalized with bio-inspired Pd catalysts and their superior hydrogen sensing performance

Abstract

Macroporous WO₃ nanotubes (NTs) functionalized with nanoscale catalysts were fabricated using coaxial electrospinning combined with sacrificial templating and protein-encapsulated catalysts. The macroporous thin-walled nanotubular structures were obtained by introducing colloidal polystyrene (PS) particles to a shell solution of W precursor and poly(vinylpyrrolidone). After coaxial electrospinning with a core liquid of mineral oil and subsequent calcination, open pores with an average diameter of 173 nm were formed on the surface of WO₃ NTs due to decomposition of the PS colloids. In addition, catalytic Pd nanoparticles (NPs) were synthesized using bio-inspired protein cages, i.e., apoferritin, and uniformly dispersed within the shell solution and subsequently on the WO₃ NTs. The resulting Pd functionalized macroporous WO₃ NTs were demonstrated to be high performance hydrogen (H₂) sensors. In particular, Pd-functionalized macroporous WO₃ NTs exhibited a very high H₂ response (R[subscript air]/R[subscript gas]) of 17.6 at 500 ppm with a short response time. Furthermore, the NTs were shown to be highly selective for H₂ compared to other gases such as carbon monoxide (CO), ammonia (NH₃), and methane (CH₄). The results demonstrate a new synthetic method to prepare highly porous nanotubular structures with well-dispersed nanoscale catalysts, which can provide improved microstructures for chemical sensing.