Study On The Defect Regulation And Room-temperature Hydrogen Sensing Properties Of The In-doped MoO₃ Nanoribbons

Hydrogen energy is considered to be a green,non-polluting,high-energy,non-toxic,recyclable and ideal clean energy alternative to traditional fossil energy sources.Hydrogen is small and easy to leak and spread rapidly in the environment,and it is flammable and explosive,which causes serious safety problems in the process of hydrogen production,transportation and storage.Therefore,the development of hydrogen sensors with high sensitivity and superior performance is an urgent goal to ensure the safe and stable development of hydrogen energy and its industrial chain.Therefore,developing hydrogen sensors with high response sensitivity and superior performance will be an urgent goal to ensure the safe and stable development of hydrogen energy and its industrial chain.Semiconductor resistive hydrogen sensor is widely used in the field of hydrogen security detection because of its high stability,low cost and high sensitivity.MoO₃semiconductor one-dimensional nanomaterial with high aspect ratio,large specific surface area and many active sites on the surface are one of the ideal materials for developing gas sensors.However,most of the existing MoO₃-based hydrogen sensors operate at relatively high temperature,which leads to high power consumption and poor selectivity,and thus many security risks.Therefore,it is necessary to develop a high performance and high sensitivity semiconductor hydrogen sensor operating at room temperature.In this paper,In-doped MoO₃ nanoribbons were prepared by hydrothermal method,and the influence of In doping amount on phase,size,composition and morphology of MoO₃ nanoribbons were studied,and the effects of doping modification on the hydrogen sensitive properties of materials were systematically explored.The main research results are as follows:（1）In（NO₃）₃·4.5H₂O was used as the indium source to synthesize the In-doped MoO₃nanoribbons of each component by hydrothermal method.The results show that the doped MoO₃remains as nanoribbons with good dispersion and no other impurities on the surface.The doped MoO₃is still in the orthorhombic phase and the lattice structure is not changed,and In enters the MoO₃lattice as In³⁺to replace Mo⁶⁺.In addition,In-doped MoO₃can introduce impurity energy levels and thus reduce the forbidden band width of MoO₃,so that the electrons can jump with less energy excitation,and the doping effectively increases the active sites in the material,which can promote the gas-solid reaction activity of gas and material to a certain extent.（2）Hydrogen sensor devices based on In-doped MoO₃nanoribbons were assembled to investigate the effects of different indium doping concentrations on the electrical properties of the devices and on the hydrogen-sensitive performance.The results show that the prepared In-doped MoO₃materials and Pt/Ti electrodes have good ohmic contacts between them,and the resulting MoO₃nanoribbons at each component doping concentration exhibit good room-temperature hydrogen-sensitive performance,and the room-temperature hydrogen-sensitive response of the devices is gradually enhanced with increasing the In doping concentration from2 at%to 6 at%doping concentration,and the hydrogen-sensitive response at 6 at%doping However,increasing the In doping concentration to 10 at%leads to a gradual decrease in the room temperature hydrogen sensitivity performance.The nanoribbon sensor based on 6 at%In-doped MoO₃doping concentration also exhibits good repeatability,selectivity,and long-term stability.（3）The hydrogen-sensitive response mechanism of In-doped MoO₃is calculated and analyzed based on the first-principles of density generalization theory,and the adsorption process of surface oxygen and hydrogen molecules and the reaction process are simulated by replacing one Mo atom with one In atom in the In-doped MoO₃model.First-principles calculations show that in air,oxygen molecules strongly interact with the In-doped MoO₃material and spontaneously adsorb on its surface,trapping electrons and forming adsorbed oxygen,which leads to a lower carrier density of In-doped MoO₃and exhibits a higher resistance in air.In the hydrogen-containing atmosphere,H₂ diffusion interacts with the pre-adsorbed O₂ to generate H₂O.through the feedback effect,electrons are released into the In-doped MoO₃,which leads to an increase in the carrier density and a decrease in the resistance of the doped MoO₃,resulting in the material exhibiting good room-temperature n-type hydrogen-sensing properties,which corresponds to the hydrogen-sensing properties of In-doped MoO₃.