Controllable Preparation And NO_x Gas Sensing Properties Of Three-dimensional Honeycomb Carbon Composites

Nitrogen oxides （NO_x） are mainly composed of two toxic and harmful gases,nitric oxide（NO）and nitrogen dioxide（NO₂）.NO_x will cause serious harm to the environment,and at the same time,NO_x will also cause serious harm to human organs.Therefore,it is urgent to develop a highly sensitive trace NO_x gas sensor with high sensitivity at room temperature to protect people from NO_x.In this paper,a three-dimensional honeycomb nitrogen-doped porous carbon material（N-GC）was synthesized by a combined direct carbonization method,and Fe₂O₃/Fe@N-GC and Bi OCl/N-GC nanocomposites were prepared in a controlled manner using this as a matrix.The gas-sensitive properties of the composites to NO_xwere investigated,and the gas-sensitive mechanism was discussed.First,a simple polymer direct carbonization method was used to prepare highly dispersed Fe₂O₃/Fe nanoparticles embedded in honeycomb-like nitrogen-doped graphitic carbon（Fe₂O₃/Fe@N-GC）on.The prepared Fe₂O₃/Fe@N-GC composites consist of a three-dimensional（3D）supported interconnected graphitized carbon framework,and the unique structure not only avoids material aggregation,but also effectively promotes charge transfer and better provides more reaction interfaces between gas molecules and materials.Combining the combined advantages of Fe₂O₃/Fe,N-doped graphitic carbon,high specific surface area and unique three-dimensional structure,the optimized Fe₂O₃/Fe@N-GC-700 sensor has good sensitivity and selectivity for NO₂ gas detection at room temperature:the gas-sensitive response value for 100 ppm NO₂ is 25.48,the response time is 2.13s,the recovery response time is The Fe₂O₃/Fe@N-GC composite has a simple preparation method and fast gas-sensitive response characteristics,which facilitates the development and design of（based on）3D honeycomb structured composites for more promotion and application.Then,a simple oil bath condensation reflow method was used to form Bi OCl/N-GC composites by in situ growth of flower-like Bi OCl（Bi OCl NFs）on three-dimensional honeycomb nitrogen-doped graphitic carbon（N-GC）.The N-GC graded structure effectively improves the dispersion of Bi OCl NFs,which increases the contact area with NO_xgas molecules.Thanks to the Bi OCl/N-GC-1 composite graded structure,the（102）and（101）faces of Bi OCl with suitable NO_x adsorption energy and electron transfer properties,the abundant mesopores and large specific surface area of N-GC,the formation of p-p heterojunctions,N doping and chemisorption of oxygen,the optimized Bi OCl/N-GC-1 The optimized Bi OCl/N-GC-1 composite sensor has good gas response to NO_x gas at room temperature:the gas response value is up to 52.54 for 100 ppm NO_x,the response time is 3.2s,and it has low detection limit（10 ppb）and long-term stability of 12 weeks.