Controlled Growth And Assembly Of Biomass-Derived Functional Carbon Materials Based On Hydrothermal Carbonization Process

Because of the large surface areas,large porous volumes.inert chemical properties,high conductivity,good biocompatibility,and so on,functional carbon materials have been widely used in space and aeronautics,autos,electron,machinery,chemical,textile and medical industries.In order to meet the urgent need of new functional carbon materials for the development of society,the design and exploration of nano-and micron-carbon materials with special morphological and porous structures have been one of the key research directions in the field of materials synthesis.The common synthetic strategies,such as chemical vapor deposition,arc discharge and pyrolysis methods,always suffer from the drawbacks of complicated preparation process,high cost,and environmental pollution.Therefore,more and more scientists start to explore more simple.sustainable,low-cost and green synthetic routes to prepare nano-and micron-carbon materials.Among them,hydrothermal carbonization(HTC),which uses natural renewable biomass and its derivative as carbon source and water as medium,has received significant attention.Through the hydrothermal process with low temperature(150-350 ?)and self-generated pressure,biomass can be translated into carbonaceous spheres with hundreds of nano to tens of micron.Although this HTC method shows distinguished advantages,it is still in the initial exploration stage in terms of morphology and pore channel regulation.Thus,this paper focus on the regulation of morphological and porous structures of HTC carbonaceous materials.The main results are summarized as follows:1.Controlled synthesis of monodispersed nanospheres and micron spherical superstructuresCarbonaceous spheres produced by HTC method always suffer the common problems of cross-linking and wide size distribution,which limit their applications in heterogeneous catalysis,biomedicine and so on.Herein,poly(4-styrenesulfonic acid-co-maleic acid)sodium salt(PSSMA)is designed and choosed as structure-directing agent,and successfully synthesize monodispersed nanospheres with size less than 400 nm.In addition,monodispersed nanospheres with sizes between 120 to 360 nm can be obtained with the variety of reaction time,temperature,and glucose concentration.Furthermore,spherical superstructures constructed from nanoparticles are synthesized in the presence of both PSSMA and hydrochloric acid,and their sizes could be regulated from 1.4 to 5.2 ?m with the change of PSSMA and acid concentrations.The obtained carbon materials are loaded with Ru nanoparticles to act as heterogeneous catalysts for the hydrogenation of methylbenzene,showing a remarkably high activity and selectivity2.Kinetics-controlled synthesis of hierarchical porous carbons(HPCs)with adjusted poresThe carbonaceous materials prepared by direct HTC of biomass have poor pore structures,which limits their applications in adsorption and desorption,heterogeneous catalysis,energy storage and translation,etc.In this part,HPCs are fabricated with the variety of reaction kinetics in the presence of soft template F127.At low reaction rate,flower-like and layered HPCs with ordered mesoporous structure(3.2 nm)are prepared.With the increase of reaction rate,nucleation rate rapidly increases,and mesoporous nanoparticles with diameters ranging from 372 to 32 nm are generated.Subsequently,the aggregation of these nanoparticles leads to HPCs with tunable mesopores and macropores.In addition,Pt nanoparticles are in suit reducted and encapsulated in HPCs with ordered mesoporous structure,the as-made catalyst reliazes the size-selected hydrogenation of alkenes3.Cooperative assembly of asymmetric carbonaceous bivalve-like superstructures from two kinds of building blocksBased on the above two points,carbonaceous bivalve-like superstructures are synthesized when both PSSMA and F127 are introduced into the reaction system.Due to the fast reaction rate,both carbonaceous solid particles and micelles as two kinds of building blocks are generated in the early stage.Solid particles tend to aggregate to spherical clusters,while micelles are inclined to aslf-assemble into hexagonal morphology.The assembly and growth of micelles on the[001]direction limit the growth of solid particles,leading to the formation of carbonaceous bivalve-like superstructures.Owing to the unique porous structure and high surface area,the carbon bivalve-like superstructures are shown to enhance the performance of supercapacitors4.Controlled synthesis of anisotropic mesoporous nanorods,nanowires and teeth-like superstructuresThrough the further regulation of reaction kinetics,the synthesis of anisotropic mesoporous nanorods,nanowires and teeth-like superstructures is realized.Products prepared in a heterogeneous polymerization system always tend to become spherical in shape due to the minimized interfacial free energy between them and medium Herein,cylindrical micelles will assemble into mesoporous nanorods with PSSMA stabilizing micelles and products.While in the presence of increased amount of PSSMA,smaller nanorods will further assemble into teeth-like superstructures.In addition,fabrication of nanorods and nanowires with tunable sizes can be further achieved by adding trimethylbenzen.With the anisotropic structure in hand,as expected,the Ru based nanohybrids serve as active and stable catalysts for the hydrogen evolution reaction5.Patterning carbon surfaces with biomass-derived mesoporous orientation-adjustable functional polymersTo extend application field of hydrothermal reaction and caron materials,a simple and efficient patterning method is developed to coat carbon surface with monolayer functional polymers.Core-shell structures are formed by micelles assembly and growth on the surface of carbon materials.At low reaction rate,cylindrical micelles will grow into mesoporous channels parallel to the surface.At high reaction rate,spherical micelles will grow into mesoporous channels perpendicular to the surface.In summary,we have developed polyeletrolyte-assisted method,kinetics-controlled soft-templating route,cooperative assembly strategy and so on for the preparation of functional carbonaceous materials with various morphologies and pores.These researches will contribute to the further design,synthesis and improvement of HTC materials,and these methods could be applied to mass production.