Enhanced formaldehyde sensing performance at ppb level with Pt-doped nanosheet-assembled In2O3 hollow microspheres

Highlights: • The 1 at% Pt-In₂O₃ composites can detect formaldehyde at ppb level. • High response, quick response-recovery and excellent selectivity were achieved. • The composites also gave good repeatability and cycling stability. • The optimal operating temperature is as low as 120 °C. Monitoring trace formaldehyde gas in air is of critical importance because of its high toxicity and threat to health, which is rather difficult at ppb level, especially at high humidity. Here, Pt-doped In₂O₃ composites consist of nanosheets with excellent formaldehyde sensing performance were prepared by a two-step method. The as-prepared 1 at% Pt-In₂O₃ composites give the best sensing performance toward formaldehyde gas with higher response, better selectivity and short response-recovery time at a low operating temperature (120 °C) compared to the pure In₂O₃. Its response is about 3 times as large as that of pure In₂O₃ to 10 ppm formaldehyde at 120 °C. The response time of the 1 at% Pt-In₂O₃ composite is less than 2 s and its recovery time is 51 s. In particular, it can detect down to 60 ppb formaldehyde in a wide range of relative humidity (25%–90% RH). The enhanced sensing properties of the composites should be attributed to the high catalytic activity of Pt/PtO₂ nanoparticles decorated on the surface of In₂O₃ hollow microspheres and the Schottky barrier between Pt species and In₂O₃.