Bimetal Ag NP and Au NC modified In2O3 for ultra-sensitive detection of ppb-level HCHO

Detecting trace ppb-level of formaldehyde (HCHO) in indoor ambient and human exhaled breath using metal oxide semiconductor (MOS) gas sensor has attracted increasing attention. Herein, Ag nanoparticles (Ag NP) modified In2O3 and Au nanocage (Au NC) modified In2O3 as well as bimetal Ag NP and Au NC co-modified In2O3 were successfully prepared via one-step microwave-assisted solvothermal method and were used to construct semiconductor gas sensor. It is exciting to observe that the sensor based on Ag6Au1/In2O3 exhibits the highest response of 277 toward 5 ppm HCHO at low operating temperature (170 °C), which is about 7 times, 38 times and 102 times higher than 6 wt. % Ag/In2O3, 1 wt. % Au/In2O3 and pristine In2O3, respectively. Moreover, the selectivity and detection limit (down to 26 ppb) of Ag6Au1/In2O3 sensor to HCHO have been proven to be greatly improved. This excellent sensing performance indicates that the proposed bimetal Ag and Au co-modification with synergistic catalysis effect offers an effective design for highly sensitive and efficient HCHO detection devices. Moreover, the mechanism of HCHO sensing with Au and Ag co-loaded In2O3 was explored by the calculations obtained from first-principle density functional theory studies.