In-situ Microscopic Observation And Enhanced Preparation Of Supported Carbon-based Catalytic Materials

Supported carbon-based catalytic materials are one of the wordwide frontiers and hotspots for catalysis scientific research,and have important applications in the chemical,energy,and environmental fields.Among them,the dispersion of catalytic active sites on the surface of the carbon-based carrier,the size of the particle size,and the exposed crystal faces have a significant impact on the catalytic performance.Therefore,the controllable preparation and high performance of supported carbon-based catalytic materials face two key challenges:one is the need to realize the observation and quantitative analysis of the material transformation phenomenon at nano-micro scale experimental level,especially for the mixing,transfer,reaction behavior and evolution mechanism of middle molecules and their aggregates,thus to clarify the regulation law of the synergistic effect of nano-microscale mass transfer and reaction on the structure and performance of materials,so as to guide the controlable preparation and engineering scale-up of carbon-based supported catalytic materials;Second,realize the precise regulation of molecular to nanomicro scale reaction-mass transfer during material preparation and engineering scale-up,so as to improve the catalysis of the catalytic material on activity,selectivity and stability,and reduce the energy consumption and material consumption in material preparation process.Based on this,this thesis has focused on in-situ microscopic observation and enhanced preparation of supported carbon-based catalytic materials.The main work includes the following aspects.(1)Aiming at the in-situ observation and quantitative characterization of the dynamic evolution of nano-scale structure during the preparation of supported carbon-based catalytic materials,based on computational fluid dynamics simulation and experimental research,a sample heating wire assembly for in-situ environmental transmission electron microscopy is proposed.The surface welding type processing method,compared with spot welding type,has reduced the resistance deviation by 90%;the nitrogen-doped carbon dots/ZIF-67 metal organic framework material mixture is heated to prepare the metal cobalt-supported carbon-based catalytic material as an example for the in-situ observation of the mixture from room temperature to 1000?,and the quantitative characterization of the precipitation-migrationaggregation process was realized;The liquid-phase in-situ transmission electron microscope was used to study the loading process,it was observed that the metal ions were first adsorbed by the functional groups of graphene surface,and then the OH-in the solution was captured and the process of in-situ precipitation growth was completed.(2)The liquid marble(LM)micro-reactor with long life and easy temperature control characteristics is constructed,which is realized by uniformly wrapping nanoparticles on the surface of the droplet.And,encapsulating LM in an organic solution to obtain "liquid marbles in liquid",The "coat" effectively avoids the evaporation of the internal liquid,so that the liquid marbles can exist stably for several weeks without deforming or breaking.Compared with the exposed droplets in organic solvents,its lifespan is increased by about 1000 times.Through the precise temperature control of the organic solvents,the temperature of the liquid marbles can be controlled efficiently,which is a micro-fluid.Combined computational fluid dynamics theoretical calculation analysis with experimental research,it is found that as the size of droplets decreases,the renewal rate of the phase interface increases significantly,which is conducive to molecular mass transfer and mixing,provides guidance for the strengthening of the preparation process of supported carbon-based nanomaterials.(3)Aiming at the characteristics of "multi-component doping and multilevel structure" of supported carbon-based catalytic materials,a high-gravitybased process intensification method is proposed to prepare supported carbonbased catalytic materials.The molecular mixing and mass transfer in the reaction precipitation process effectively control the explosive uniform nucleation of the precursors,and realize the enhanced nano-micro-scale molecular mixing in the macro-reactor.The graphene-supported iron oxide catalytic material is prepared,and the supported iron oxide particles have an average size of 4.4 nm and the size distribution is uniform.It exhibits high catalytic activity in model reactions such as photocatalytic degradation of methylene blue.(4)The graphic carbon nitride(g-C3N4)catalytic material supported by nickel phosphide(Ni2P)nanoparticles was prepared by the high-gravity exfoliation coupled with reaction precipitation method,in which the mixed mass transfer was enhanced.The layer g-C3N4 shows fold morphology.The process of precipitation and loaded Ni2P particles is further enhanced by high gravity to prepare a Ni2P/g-C3N4 catalyst material with uniform particle distribution.When the loading amount of Ni2P is 5 wt%,the photocatalytic hydrolysis rate for hydrogen production is 561 ?mol·g-1·h-1,showing excellent photocatalytic performance.