Big Specific Surface Area Of Functional Nanomaterials Assembled Based On Template Method

Functional nanomaterials with large specific surface are widely used in electrochemistry,optics and biomedicines,due to their large active area and surface atomic exposure ratio.It is an effective way to construct nanomaterials with large specific surface by template methods controlling their orientation,morphology and size.In this thesis,nitrogen doped carbon(NC)with optimized laminated spacing is used as the template to obtain manganese oxide(MnOx)as electrocatalyst performing excellent oxygen reduction reaction(ORR)performance.The electrocatalyst Ni3S2/MnS with large active surface area obtained by the Ni foam(NF)template achieves high speed in water splitting.Monodisperse barium carbonate nanorods(BaCO3 NRs)with large surface area are fabricated by using pore channels template of polycarbonate(PC)membrane and self-assembly polyelectrolyte layers.This thesis not only deepens the understanding of the correlation between the structure and properties of nanomaterials with large specific surface,but also provide guidance in experiment,theory and applications for the assembly and catalytic properties of nanomaterials with large specific surface based on template method.The morphology and conductivity of manganese oxides(MnOx)seriously affect their electrocatalytic activities.In chapter three of this thesis,the nitrogen doped carbon(NC)laminate arrays with narrow laminate spacing are obtained by templating the bidirectional ordered ice crystals and adjusting the molecular weight and concentration of soluble chitosan.Then MnOx nanopyramids with uniform distribution,composed of MnOx nanosheets,are vertically grown on the surface of NC laminate arrays as template.The NC consists of hierarchical laminate arrays,closely connecting the uniform MONPMs and ensuring superior electrical conductivity.The MONPMs contain rich oxygen vacancies(OVs),favorable for catalyzing ORR.MONPMs/NC laminate arrays have a large specific surface area(409.7 m2 g-1),hierarchical porous structure,a large ratio of N/C atoms(10.62 at%),and rich OVs.This unique structure of MONPMs/NC not only ensures the full exposure of MONPMs active sites,shorten the diffusion time of O2 between laminate arrays,but also increases the diffusion and adsorption of O2 on the surface of MONPMs/NC,thus enhancing the ORR performance.The electrocalatalytic activity of MONPMs/NC is better than those of so far reported MnOx and MnOx/carbon composited materials.The development of highly active and stable non-noble metal electrocatalysts for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)bifunctional performances for meeting demands of green energy is crucial for efficient water splitting.In chapter four of this thesis,such electrocatalysts are obtained,first in two-step hydrothermal reactions to form Ni3S2/MnS nanosheets on Ni foam(NF/Ni3S2/MnS),then by slightly electroxidizing the Ni3S2/MnS to generate tremella-like Ni3S2/MnS-O with ultrathin nanosheets and abundant OVs(denoted as NF/T(Ni3S2/MnS-O))favorable for electrocatalyzing HER and OER.Benefiting from the abundant OVs,large active surface area,ultrathin nanosheets on tremella-like NF/T(Ni3S2/MnS-O)and hierarchical porous structure,NF/T(Ni3S2/MnS-O)shows high catalytic performance,including lower overpotential and electrochemistry stability for both HER and OER than so far reported MnOx and other metal oxides/sulfides.The NF/T(Ni3S2/MnS-O)directly used as bifunctional electrodes for overall water splitting exhibits a low voltage of 1.54 V with a low overpotential of 0.31 V at a current density of 10 mA cm-2,a fast H2 and O2 evolution speed of 4.13 and 2.04?mol min-1 and a good electrochemistry stability with unchanged current density of 10 mA cm-2 for 50 h.The morphology of inorganic crystals is difficult to be controlled though soluble polymers and other organic additives in solution could be lower down its crystallization process.It has been reported that CaCO3 NRs in pore channels of polycarbonate membrane(PC)can be controlled by polyacrylic acid(PAA).However,compared with PAA,the effect of more rigid poly(sodium 4-styrene-sulfonate)(PSS)on the crystallization of nanomaterials controlled by template is not clear.In chapter five of this thesis,barium carbonate(BaCO3)within the controllable morphology of nanorods(NRs)is prepared by employing pore channels of a polycarbonate(PC)membrane as the template,consisting of PSS and polyelectrolyte layers(PSS/polyallylamine hydrochloride)1.5((PSS/PAH)1.5)assembled on the inner pore walls to regulate nucleation and growth of BaCO3.The formation mechanism of BaCO3 NRs is provided.The polymer-inorganic precursor PSS-BaCO3 generated from the reaction of Ba2+ and CO32-induced by PSS,infiltrates into the inner pore.BaCO3 phase-separates from PSS-BaCO3,initially nucleates and crystallizes and forms BaCO3 microcrystals in pore channels.BaCO3 microcrystals gradually increase along the direction of each end to the middle,until filling the whole channel.The interaction between(PSS/PAH)1.5 and PSS-BaCO3 lower down the crystallization process,thus ensuring BaCO3 filling the whole channel,forming NRs.