Oxygen Vacancy\nMediated-Bismuth Molybdate/Graphitic\nCarbon Nitride Type II Heterojunction Chemiresistor for Efficient\nNH<sub>3</sub> Detection at Room Temperature

Metal oxide-based chemiresistive gas sensors are expected\nto play\na significant role in assessing human health and evaluating food spoilage.\nHowever, the high operating temperature, insufficient limit of detection\n(LOD), and long response/recovery time restrict their broad application.\nHerein, 3D Bi<sub>2</sub>MoO<sub>6</sub>/2D Eg-C<sub>3</sub>N<sub>4</sub> heterocomposites are developed for advanced NH<sub>3</sub> gas sensors with RT operational mode. Utilizing the synergetic engineering\nof micro-nanostructure, surface oxygen vacancies, and well-defined\nType II n–n heterojunctions, BMOCN3 demonstrated superior NH<sub>3</sub> sensing properties at 23 °C, including the high response\n(S = 13.6 at 10 ppm), fast response/recovery speed (8/30 s), excellent\nselectivity, and low LOD (166 ppb). Based on the experimental, DFT,\nand MD studies, the improved sensing performance can be ascribed to\naccelerated charge transfer, superior redox capacity, and improved\nadsorption/desorption kinetics. Moreover, the practical application\nin rapid exhaled NH<sub>3</sub> biomarker detection of the as-fabricated\ngas sensor was preliminarily verified. This work highlights that the\nnovel synergetic engineering can effectively modulate the electronic\nstructure and charge transfer, offering a rational solution for room\ntemperature chemiresistive gas sensors.