| In 21st century,the rapid development of industry with huge energy consumption caused that the mankind is faced with the exhaustion of the non-renewable energy(e.g.,fossil fuels)and a series of serious environmental problems.Hence,it is urgent to develop new clean energy materials and make full use of solar energy and other renewable energy sources.There are plenty of biomass resources in nature.Among these biomass resources,the natural cellulose substances possess the rich production,good biological degradability,biocompatibility,flexibility and mechanical strength,and the complex interactions between cellulose molecules endow the natural cellulose substances with unique three-dimensional hierarchical structure,porosity and large specific surface area.Natural cellulose materials,therefore,are good biological templates,and the rich active surface hydroxyl groups enable a variety of the guest materials to self-assemble on the surface of cellulose.Herein,the natural cellulose substance(ashless quantitative filter paper)was applied as the template to direct the self-assembly of a lot of oxide molecules on the surface of each cellulose nanofiber.Then,various new advanced functional nanomaterials with specific structure of natural cellulose template and the specific properties of the guest materials were obtained through differently subsequent treatment,which show potential applications in the fields of photoelectrical conversion systems and lithium-ion batteries.The main content is described as follows:1.Photosystem ?/porous TiO2 nanotube network photoanode system:On the basis of the covalent bonding between the surface hydroxyl groups of cellulose and the titanium alkoxide,titania thin gel layers were layer-by-layer self-assembled on each cellulose nanofiber of filter paper,and then,the cellulose template was calcined in air,resulting in the anatase titania nanotube material which exactly replicated the hierarchical porous network structure of the template.The electrode substrate surface was modified by the fabricated titania material,followed by assembly of photosystem ?(PS?)protein purified from spinach leaves with function of light-induced water splitting on the electrode.Thus,a novel protein/semiconductor hybrid biomimetic photoanode system was successfully established.Due to the optimization of the flat structure of the electrode surface by titania nanotube material,the protein loading on the electrode surface was increased.Moreover,the synergistic effect was exited between PSII and titania,and the Z-scheme electron transfer chain in natural photosynthesis process was simulated by the electron transfer pathway between PS? and titania.This PS?/TiO2 hybrid photoanode system possessed good photoelectrochemical performance.When the hybrid photoanode system was applied for solar energy conversion and electricity generation,enhanced photocurrents were achieved under white light irradiation similar to the sunlight,and LEDs were driven under a certain condition.2.Photosystem ?/nanotubular indium-tin oxide film co-assembled photoanode system:On the basis of the covalent bonding between the surface hydroxyl groups of cellulose and the indium/tin alkoxides,indium/tin oxides(ITO)thin gel layer/cellulose composite material was prepared.Then,the cellulose component was removed from the as-prepared composite material by calcination in air,giving a nanotubular ITO film with cellulose templated hierarchical porous network structure.This ITO material possessed a relatively higher optical transmittance in the visible region,and a relatively higher electrical conductivity given by the proper In/Sn molar ratio.The modification of the flat electrode substrate was realized by pasting the fabricated ITO film on it by the conductive gold adhesive,followed by assembly of the PSII protein in the porous network structure,resulting in a novel semi-artificial PSII/nanotubular ITO film hybrid photoanode system.The nanotubular ITO film modified on the electrode surface improved the protein loading effectively.Moreover,the specific structure,superior optical and electrical properties of the nanotubular ITO allow for enhanced electron transfer efficiency in this photoanode system.When the hybrid photoanode system was employed for solar energy conversion and electricity generation,relatively higher photocurrent responses were achieved under white light irradiation similar to the sunlight,presenting a superior photo-to-current conversion efficiency and good photoelectrochemical performance.3.Nanofibrous polypyrrole/silicon composite material:On the basis of the covalent bonding between the surface hydroxyl groups of cellulose and the silane,silica thin gel layer/cellulose composite was prepared by means of sol-gel method,which was subjected to calcination in air to give a nanotublar silica material.Then,the silica nanotube was transferred to silicon nanofiber composed of silicon crystal nanoparticles by means of magnesiothermic reduction.The pyrrole adsorbed on the surface of silicon nanofiber was in-situ chemical polymerized,resulting in polypyrrole(PPy)nanoparticles deposited on the silicon nanofiber uniformly and completely.The fabricated nanofibrous PPy/silicon composite material inherited the three-dimensional porous network structure of the cellulose template.The hybrid material was used as an active anode material for lithium-ion batteries,the structural integrity of material and the crystal phase of silicon were well maintained during the charge/discharge processes,showing high reversible capacity,high cycling ability and enhanced rate performance.4.Vanadium-doped titania hybrid material:On the basis of the covalent bonding between the surface hydroxyl groups of cellulose and the titanium/vanadium alkoxides,titania/vanadia hybrid thin gel layers were layer-by-layer self-assembled on each cellulose nanofiber of filter paper by means of surface sol-gel method,and then the composites were subjected to flame burning and calcination in air to remove the cellulose template,respectively,giving a series of vanadium-doped titania hybrid materials.Among them,the portion of vanadium doping was controlled by the molar ratio of titanium alkoxide and vanadium alkoxide.By comparison with the hybrid materials prepared by calcination,the phase separation of titania and vanadia as well as the crystal particles aggregation and growth in the process of phase transformation was suppressed to a certain extent,and vanadium doping into titania crystal lattices was promoted by means of flame burning.Nanofibrous vanadium-doped rutile titania hybrid materials were fabricated and replicated the cellulose templated hierarchical structure precisely,and the nanofibers were composed of nanoparticles with small and uniform sizes.In addition,the phase transformation of titania materials prepared by calcination were further studied.It is indicated that the phase transformation temperature of titania was decreased effectively by vanadium doping into titania crystal lattices and by the layer-by-layer self-assembly method with cellulose as a template,and the initial anatase titania was completely transformed into rutile titania at a relatively lower calcination temperature of 600 ?. |
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