Polyoxometalate as pivotal interface in SnO2@PW12@TiO2 coaxial nanofibers: From heterojunction design to photocatalytic and gas sensing applications

In semiconductor composite materials, heterogeneous interfaces often exhibit improved performances compared to mixed composites. Polyoxometalates (POMs), have been regarded as semiconductors and used as electron acceptors in recent years. Herein, to construct POMs/semiconductor heterogeneous interfaces for highperformance photocatalyst and gas sensor, we introduced phosphotungstic acid (PW12) as a pivotal interface into SnO2/TiO2 composite. One-dimensional SnO2 @PW12 @anatase/rutile-TiO2 core-middle-shell coaxial nanofibers are fabricated utilizing facile electrospinning. The triple-layer structure can form tandem TiO2/PW12 and PW12/SnO2 heterogeneous interfaces. The SnO2 @PW12 @TiO2 nanofibers exhibit excellent photocatalytic activities. The optimal degradation efficiency of tetracycline is 73.8 % in 30 min, which is significantly higher than that of PW12-free SnO2 @TiO2 and SnO2/PW12/TiO2 mixed nanofibers. By mechanism analysis, the improvement can be ascribed to the tandem TiO2/PW12, PW12/SnO2 dual Z-Scheme heterogeneous interfaces. They could promote electrons migration and inhibit the recombination of photo-induced electron-hole pairs. Moreover, gas sensing performances of the SnO2 @PW12 @TiO2 nanofibers are investigated. The optimal sensitivity response to 100 ppm acetone is 8.2. It is 3.73 times higher than that of PW12-free nanofibers. Selectivity and other sensing parameters are also boosted. The research results provide new thoughts for exploiting high property photocatalysts and gas sensors by introducing POMs as a pivotal functional interface.