| Colloidal micro/nanospheres have attracted wide attention because of their intrinsic properties such as precise controllable size,chemical composition,internal structure and crystallinity.In recent decades,scientists have successfully synthesized a series of representative colloidal spheres,such as colloidal silica spheres,polystyrene colloidal spheres,phenolic resin colloidal spheres,etc.The appearance of each colloidal sphere has promoted the development of nanoscience.These colloidal spheres play important roles in the fields of biomedicine,colloidal catalysts,active material encapsulation and photonic crystals.Especially,highly cross-linked polymer colloidal spheres such as phenolic resins can be converted into porous carbon colloidal spheres by a high temperature pyrolysis.The obtained porous carbon colloidal spheres are widely used in energy conversion and storage,gas adsorption and separation,and electrocatalysis.However,the synthetic strategy of these colloidal spheres still has some limitations:(1)Current syntheses mostly focus on the improvement of traditional colloidal spheres,while the exploration of new reactions for colloidal spheres is insufficient;(2)The harsh synthetic conditions and toxic solvents increase production costs;(3)Most of the synthetic colloidal spheres own poor thermal stability;(4)The control of porous structures is still challenging.These shortages have limited the large-scale synthesis and applications of colloidal spheres.Thus,it is necessary to explore synthetic strategies with mild conditions to produce functionalized colloidal spheres.This thesis contains the exploration of new chemical reactions suitable for the formation of polymer VI colloidal spheres,the design of synthetic strategies under mild conditions,the syntheses and applications of nanocomposites based on polymer colloids,and the control of porous structures in polymer colloidal spheres.The major achievements are described as following:(1)Based on the self-polymerization of 2,6-diaminopyridine(DAP),we have designed a facile strategy to rapidly synthesize a totally new type of polymer colloidal nanospheres.The obtained polydiaminopyridine nanospheres(PDAP)have a uniform particle size distribution(76~331 nm),and the size of PDAP nanospheres can be precisely adjusted by two programmable factors,providing more composite modes and predictable sphere sizes.The PDAP nanospheres are rapidly formed within 5 minutes and at least 11 g of PDAP powder can be obtained from 750 m L of the reaction solution,still with high yield of ~95 %.The PDAP nanospheres can be easily converted into microporous carbon nanospheres with high surface areas and high N content up to 24 wt%.The obtained N-doped microporous carbon nanospheres show excellent CO2 adsorption properties.CO2 areal capacities of microporous carbon nanospheres(~9.8 ?mol m-2)is the highest among the previously reported porous carbons.As-synthesized PDAP can not only encapsulate conventional metal and oxides nanoparticles to form core-shell composite nanospheres,but also stabilize ultra-small metal nanoparticles during the thermal reduction process by the nitrogen sites from sphere frameworks.The Pd nanoparticles stabilized by PDAP are very active for solvent-free aerobic oxidation representative alcohols with high selectivity and remarkable turnover frequencies.(2)Taking advantages of the abundant nitrogen sites in PDAP,we use PDAP as a media to immobilize Pd ions in the polymer.This Pd-containing PDAP(PDAP-Pd)can be used to encapsulate various oxide colloidal particles such as non-metal oxide Si O2,transition metal oxide Ti O2 and rare earth metal oxide Ce O2 colloidal spheres,to synthesize a series of Oxide@PDAP-Pd core-shell composites.A series of Oxide@Pd catalysts can be obtained by pyrolyzing Oxide@PDAP-Pd in air to retain palladium and oxides.Due to the excellent stabilizing effect of the Ce O2 lattice surface on Pd,the Pd species in Ce O2@Pd1 do not exist as Pd particles or Pd O particles but exist as monatomic atoms.This kind of monoatomic catalyst shows extremely high catalytic VII activity in the process of solvent-free oxidation of benzyl alcohol,with a TOFs of up to 14812 h-1.We used the same method to load Pd onto three kinds of Ce O2 with different exposed crystal planes.It was found that C-Ce O2@Pd1 exposing Ce O2(100)surface exhibited similar high catalytic activity compared to Ce O2@Pd1.This is consistent with the distribution of monoatomic Pd on the Ce O2(100)crystal plane in TEM image.Computer simulations show that the Ce O2(100)crystal plane is more conducive to the formation of oxygen vacancies than the(110)and(111)crystal planes so that palladium is easily fixed on the(100)crystal plane,and its enhanced oxygen storage capacity also promotes the oxidation of benzyl alcohol,which is the main reason for the high catalytic activity of Ce O2@Pd1.(3)We have copolymerized DAP with formaldehyde and synthesized multi-chamber polymer microspheres(MCP)using a surfactant-induced confinement polymerization strategy.The synthesis process includes two stages of polymerization: the first stage mainly realizes the initial hydroxymethylation reaction of DAP in an alkaline environment and forms unstable precursor microspheres with large caveties;the second stage achieves sufficient hydroxymethylation of DAP and dehydration condensation of methylol to ether by reducing the p H of the solution with acetic acid,the limited polymerization in the large cavity allows the cavity to be divided into a large number of small chambers to obtain a multi-chamber polymer MCP.As-synthesized MCP can be carbonized into a multi-chamber microporous carbon MCC under N2-CO2 atmosphere.This structure is favorable for the loading and fixation of cargo molecules.When MCC is used in a lithium-sulfur battery,a large amount of sulfur can be loaded and the elution of lithium polysulfide can be suppressed to achieve high cycle stability of sulfur cathode.The composite cathode containing MCC-6H can reach a specific capacity of 600 m Ah/g,and the capacity can maintain 93% of the initial value after 150 cycles.(4)We designed a series of one-pot synergetic reactions to synthesize noble metal nanoparticles@mesoporous carbon(NM@MC)core-shell colloids.The obtained NM@MC shows uniform and highly dispersed morphology,tunable size,high surface area,and clear core-shell structure with abundant mesopores.During the one-pot reaction,the raw material resorcinol and the surfactant hexadecyl trimethylammonium chloride for the synthesis of mesoporous carbon act as the reductant and coordination stabilizer for the formation of Au cores.Meanwhile,the noble metal cores accelerate the growth of phenolic resole-silica(RF-Si O2)shell by decreasing the nucleation process.Thus,the formation and encapsulation process of noble metal nanoparticles are happened simultaneously in a one-pot synthesis system.The uniform RF-Si O2 shell can protect the noble metal cores from agglomeration during the calcination process.The obtained Au@MC colloid exhibits the better catalytic performance than those of Pt@MC,Ag@MC,Au@microporous carbon and even ultra-small Au nanoparticles in the reduction of 4-nitrophenol to 4-aminopheol,thanks to the excellent catalytic performance of Au inner core and the fast mass transfer of mesoporous carbon shell.(5)We combined the diversity of coordination compounds with the excellent stability of cross-linked polymers,and designed a coordination-polymerization strategy to synthesize metal-gallic acid resin(X-GR).Experiments show that the cross-linking of formaldehyde can significantly improve the stability of metal-gallic acid complexes.The obtained X-GR can be pyrolyzed under nitrogen to obtain metal nanoparticlesfunctionalized mesoporous carbon materials(X-MC),which contains highly dispersed metal nanoparticles with a content of metal up to 20 wt%.Thanks to the diversity of coordination modes,metals in materials can be replaced with various transition metals,including Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn,etc.to synthesize X-GR and X-MC with similar structures.In addition,this strategy can also be extended to the synthesis of nitrogen-doped bimetallic catalysts.For example,simultaneous addition of Fe and Co metal sources during the synthesis process can yield bimetallic gallic acid resin(Fe CoGR).The nitrogen-doped bimetallic catalyst(Fe Co-MCN-900)showed comparable catalytic activity to commercial Pt/C in the electrocatalytic oxygen reduction reaction. |
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