Controlled Construction And Properties Of Molybdenum-based Hybrid Materials

Henan Province is rich in molybdenum resources.This thesis combines the current material research hotspots with the resource advantages of Henan Province,and optimizes the functions of related materials by tailoring the structure and composition of molybdenum-based materials,and explores new ways for the design and application of new sensing and energy storage devices.The thesis includes three parts:(1)Constructions of Pd@MoO₃ hollow microspheres for aniline sensors.The MoO₃hollow microspheres with high specific surface and porosity have been successfully prepared with a novel two-phase technique developed in our lab first.The materials can be then decorated with Pd nanoparticles for assembling side-thermal gas sensors with enhanced sensing performances on detecting aniline gas.The Pd@MoO₃ hollow microsphere with optimized amount of Pd nanoparticles loaded onto their surfaces show excellent selectivity for aniline gas,high response of 31.9 to 25 ppm aniline gas at the optimal operating temperature of 220°C,and short response/recovery time of 17/25 s.Compared to the devices assembled with MoO₃ hollow microspheres the performances of aniline sensors can be improved by about 5 times.(2)Build MoO₃/MoO₂ hierarchical structures for optimizing the performances of aniline sensors.Based on DFT calculations,the band structure of MoO₃ can be tuned by introducing MoO₂ onto its surfaces,which can enhance the adsorption of aniline.It is therefore predicted that the semiconducting MoO₃ films can exhibit higher sensing activities to aniline gas after introducing metallic MoO₂ to form MoO₃/MoO₂ hierarchical structure.This project has focused on building MoO₃/MoO₂ hierarchical structures through first producing MoO₂ hollow microspheres and then oxidizing MoO₂ into MoO₃ on their surfaces with an oxidation process at high temperature.The MoO₃/MoO₂ hierarchical structures with dynamically optimized compositions achieve highly improved responses to aniline of much lower concentrations at lower working temperature,compared to MoO₃.Specifically,the devices exhibit high response of 14.7 to 5 ppm aniline at 200°C,and the response and recovery times are 16 s and21 s,respectively,which may offer an novel pass way for constructing a novel system in-situ monitoring aniline.(3)Li batteries assembled with bowl-like O-MoS₂@C electrodes.In order to construct O-MoS₂@C electrodes,bowl-like MoS₂ particles have been first prepared with a micro-emulsion method by using CTAB surfactant as a soft template.The oxygen dopants can be then created subsequently to sulfur-rich vacancies in anion exchange reaction performed at high temperature in Ar.Simultaneously,amorphous carbon can be in-situ generated in the bowl-like particles,because of the decomposition of CTAB surfactants during the annealing process.The O-MoS₂@C electrodes assembled with the materials shows excellent performance in storing Li with an average specific capacity of?1442 m Ah g^-1 at 0.2 A g^-1and?394 m Ah g^-1 at 5 A g^-1.The reversible capacities of Li batteries assembled are 1208m Ah g^-1 after 200 cycles,and?361 m Ah g^-1 after 700 cycles,respectively.The DFT calculations performed to understand the highly enhanced Li storage performance of O-MoS₂@C electrodes further reveal that O-dopants and carbon protections can synergistically improve the thermodynamic adsorption of lithium and facilitate the kinetic diffusion of lithium.