| The rapid development of social economy and the continuous growth of population have put forward more urgent requirements for the exploration and utilization of renewable biomass resources.Wood is one of the most abundant biomass resources on Earth and has been widely used in buildings,Bridges,furniture and everyday tools since ancient times.After millions of years of evolution,wood has a large number of layered porous cellulose skeleton structures composed of hollow cells with significant anisotropy.This hierarchical structure provides a channel for the transport of nutrients required by wood during its growth,as well as a good platform for transformation into functional materials.It is an important way to solve the problems of resources,energy and environment to study and utilize wood cellulose skeleton deeply and realize the effective transformation and high value utilization of wood resources.Based on this,guided by high-value utilization of wood,this thesis carried out a series of studies on controllable construction and application of micro-nano structure of lignocellulose-skeleton,with specific contents as follows:(1)In order to solve the problems of high inorganic base consumption,resin enhancement agent pollution and limited dimensional stability due to limited compression,the lignin in wood was removed from fast-growing poplar residues by using formic acid-water azeotrope temperate system environment,and the delignification wood(DW)was prepared and hot pressed and compressed to form CW.The degradation degree of wood cellulose was measured by controlling the degree of delignification.The results showed that under mild azeotrope conditions(formic acid mol%=53%,temperature=107.6°C),lignin was basically dissolved(25.0-8.0%)after two hours of treatment,and the cellulose hydrolysis reaction was weak during the large amount of lignin extraction stage(1-2h),achieving a balance between high intensity lignin removal and low cellulose degradation.Strength tests showed that the mechanical properties of CW were affected by low cellulose degradation and high lignin removal.Furthermore,on the basis of high strength compressed wood(CW),combined with cellulose nanocrystalline(CNC)embedding,the structure of the reinforced wood(RW)was densified,and the water absorption of the wood was effectively reduced,the stability of the structure was improved,and the mechanical properties of the wood was improved.Without the introduction of heterogeneous components,the prepared RW showed excellent mechanical properties,with the maximum HV(800),flexural strength(211.3 MPa),tensile strength(183.4MPa)and tensile elastic modulus(14.0 GPa)increased by 12%,22%,11%and 16%compared with CW.Compared with natural wood,the increase is 5.3,5.2,4.1,2.6 times.It is proved that the combination of decomposition and separation of cellulose protection strategy has a positive effect on the strength properties of compressed wood,and it is also verified that CNC is a promising green wood strengthening agent.(2)To address the problems of mass transfer limitations and chemical activation contamination associated with the existence of biomass-derived carbon electrodes in powder form for supercapacitors,self-supporting wood-based supercapacitor carbon electrode materials were prepared using waste larch trimmings as raw material,combined with component separation and multi-stage carbonization methods.The wood-based carbon morphology and pore structure were regulated by controlling the delignification treatment,charring time and charring temperature.The results showed that the coupled delignification and multi-stage carbonization treatments effectively controlled the microtubular structure and porosity of the wood-based carbon.When the carbonization temperature was 800°C,the resulting sample had a stable self-supporting microtubule array structure with good porosity(surface area of 945.09 m~2/g)and a microporous content of 88%.The material has a high specific capacitance(211.3 F/g and 58.3 F/cm~3),energy density(105.6 Wh/kg~1),power density(900.0 W/kg~1)and stability(98%after 8000 cycles).By comparing with the biomass waste-derived supercapacitor electrode materials reported in the literature from multiple angles,the prepared self-supported woody carbon electrode has obvious advantages,and the biomass waste-supported carbon electrode material was constructed to initially solve the problem of mass transfer limitation posed by biomass carbon powder in the field of supercapacitors.(3)To address the problem of unification of electrode activity and stability under high current density in electrolytic hydrogen production,a wood-based cellulose skeleton prepared from waste larch trimmings by component dissociation was used as the catalyst carbon substrate precursor,and a large number of metal ions were uniformly adsorbed by the abundant hydroxyl functional groups on its surface,and a metal organic framework(MOF)layer bridging strategy was used to embed cobalt-nickel bimetallic nanoparticles(Co Ni NP)in situ in a layered charred wood framework(CW)covered by MOF-derived N-doped porous metal layers(N@Co Ni)to prepare a self-supported hydrogen precipitation reaction catalyst with a three-dimensional porous structure(Co Ni NP-N@Co Ni/CW).The results show that the introduced MOF-derived N@Co Ni metal layer can act as an effective bridge to firmly connect the porous charred delignified wood(CW)to the Co Ni NP.Meanwhile,the introduction of the metal layer not only preserves the porous properties of the wood-derived porous carbon substrate,but also effectively achieves the migration of the d-band center and the reduction of the charge impedance,which in turn ensures the rapid electron transfer and smooth adsorption/desorption of the adsorbed intermediates in the charred wood framework during strong bubble impingement generated by high current density,synergistically enhancing the electrochemical performance and stability of the catalyst.the CW,N@Co Ni layer and the synergistic effect of Co Ni NP combines the advantages of layered porous structure,abundant exposed active sites and structural stability,resulting in good activity and stability.The prepared Co Ni NP-N@Co Ni/CW hydrogen precipitation catalysts require an overpotential of only 143 m V at a current density of 100 m A/cm~2 and a Tafel slope of only 50 m V/dec,and can operate at a high current density of 100 m A/cm~2 for 90 h with negligible loss of activity. |
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