Tailoring the injection action of oxygen over top-surface of bismuth sulfide to change reactive electron transfer path for flexible NO2 sensors

Abstract

Precisely tailoring the surface electronic state of catalysts to realize the optimal design of adsorption sites is essential to the surface-related gas-sensing reaction. Herein, based on both molecular orbital theory and p-band models, we develop a brilliant surface oxygen-injected method to simultaneously enhance the overlap of energy-level alignment (ELA) and reduce the anti-bonding filling (ABF) level between surface Bi p-band and adsorbed NO2 molecule, leading to an optimal NO2 adsorption mode and sensing performance. By controlling the oxygen permeation concentrations, the weak-oxidized Bi2S3-200 catalysts with ordered core/disordered shell configuration exhibit excellent NO2 gas sensitivity (12.5 % to 1 ppm) and low experimental detection limit (100 ppb), surpassing that of most reported NO2 sensors. Ex situ XPS characterizations further demonstrate that the weak-oxidized amorphous Bi species can serve as active adsorption centers to alter the electron transfer path in NO2 atmosphere. Finally, through inserting flexible MEMS sensors array into multifunctional wireless sensing device, the Bi2S3-200 sensors can realize real-time NO2/temperature/humidity monitoring and cloud data transmission at room temperature, which thereby pave the way for the development of crop health monitor and precision agriculture.