Influence Of Wood Components On The Structure And Properties Of Wood-based Electrocatalytic Materials

Wood is a sustainable and renewable natural resource with three-dimensional porous structure and abundant active functional groups,which can be used as a selfsupporting substrate material for electrocatalysts.The preparation of electrocatalysts based on wood is a new direction for efficient utilization of wood-based functional materials and wood resources.Wood is mainly composed of cellulose,hemicellulose and lignin,and the chemical composition of wood is closely related to the catalytic performance of wood-based electrocatalytic materials.However,most of the researches use wood as a substrate to design and optimize the structure of catalytically active substances to prepare high-performance composite electrocatalysts,but do not study the relationship between the chemical components of wood substrates and the performance of electrocatalytic materials.In this paper,the selective removal of hemicellulose from wood and the selective removal of lignin from wood by hightemperature cooking with acetic acid and sodium chlorite solution were used to study the relationship between wood components and the structure and properties of wood substrates.On this basis,high-efficiency electrocatalysts were prepared by vacuum impregnation of iron and nickel ions with wood with the adjusted components as the substrate material.The main research contents and results are as follows:(1)Selective removal of hemicellulose from natural poplar wood(PW)by acetic acid solution cooking.Dehemicellulose wood substrate HW-1,HW-2,HW-3 and HW4 were prepared with hemicellulose removal rates of 20.72%,42.34%,55.40%and 75.51%,respectively.After selective dehemicellulose,the cellulose retention rate of wood was high,which were 92.23%,90.84%,90.29%and 89.60%,respectively,all of which were rich in active functional groups such as hydroxyl groups.After high temperature carbonization,the prepared dehemicellulose wood carbon(HWC)retains the structural characteristics of HW and had high porosity.The specific surface areas of PWC,HWC-1,HWC-2,HWC-3 and HWC-4 are 370 m2 g-1,463.80 m2 g-1,545.79 m2 g-1,568.50 m2 g-1 and 84.61 m2 g-1,respectively.The surface wettability and underwater air repellency of HWC are also improved,and it has good hydrophilic and air repellency.Compared with the graphitization degree(ID/IG=1.11)and carbon content(92.24%)of PWC,HWC has higher graphitization degree(ID/IG=1.03～1.05)and carbon content(94.56%～94.76%),HWC showed better conductivity.The OER performance of PWC and HWC was further compared.To achieve a current density of 100 mA cm-2,the required overpotentials for PWC,HWC-1,HWC-2,HWC-3,and HWC-4 were 914 mV,832 mV,792 mV,830 mV,and 900 mV,respectively.Among them,HWC-2 has the best electrocatalytic performance.Selective removal of hemicellulose in wood can optimize the structure and properties of wood substrates.The degree of hemicellulose removal is basically the same as the degree of structural optimization of wood substrates,and the degree of performance improvement is basically the same.(2)Selective removal of lignin from natural wood by sodium chlorite solution treatment.The wood substrates LW-1,LW-2,LW-3 and LW-4 with lignin removal rates of 19.27%,36.76%,52.85%and 79.45%were prepared.After selective removal of lignin,the retention rate of cellulose was higher,which were 96.19%,92.71%,91.04%and 89.65%,respectively,and more active functional groups such as hydroxyl groups were exposed.After carbonization,LWC retains the pore structure characteristics of LW,with higher porosity and larger specific surface area.The specific surface areas of LWC-1,LWC-2,LWC-3 and LWC-4 were 684.04 m2 g-1,764.52 m2 g-1,731.87 m2 g-1 and 610.15 m2 g-1,respectively.The surface wettability and underwater air repellency of LWC were significantly improved.Among them,the contact angles of underwater bubbles of LWC-3 and LWC-4 are greater than 150°,and they have superaerophobic surfaces,which effectively reduce the adhesion of bubbles on the catalyst s urface.LWC has a higher degree of graphitization and carbon content,the carbon content of LWC-1,LWC-2,LWC-3 and LWC-4 are 94.65%,94.90%,95.75%and 96.19%,respectively,and the electrical conductivity is also in order improve.The electrocatalytic performance of LWC was further investigated,to achieve a current density of 100 mA cm-2,the required overpotentials for LWC-1,LWC-2,LWC-3 and LWC-4 were 841 mV,808 mV,775 mV and 746 mV,respectively.Among them,LWC-4 has the best electrocatalytic performance.Within the scope of lignin removal in this study,selective removal of lignin can better optimize the structure and properties of the wood substrate,and the optimization effect is more obvious as the degree of lignin removal increases.(3)FeNi/PWC,FeNi/HWC and FeNi/LWC electro catalysts were prepared by using PW,HW and LW as catalyst substrates,respectively.The electrocatalytic performances of the three were FeNi/LWC,FeNi/HWC and FeNi/PWC in order.When the current density is 100 mA cm-2,the FeNi/LWC,FeNi/HWC and FeNi/PWC are 262 mV,293 mV and 372 mV,respectively.LW adsorbs a large amount of iron and nickel ions,and FeNi/LWC has the highest active material loading rate(20.08%),which is higher than that of FeNi/HWC(15.79%)and FeNi/PWC(11.16%).Moreover,FeNi/LWC retains the interconnected pore structure of LWC,which is more conducive to electrolyte infiltration and bubble diffusion.Wood components have a significant effect on the electrocatalytic performance of wood-based iron-nickel composite electrocatalysts.The selectively delignified wood is more suitable as a substrate material for electrocatalysts than the selectively de-hemicellulose-removed wood,and both are more suitable as substrate materials for electrocatalysts than natural wood.In this paper,the relationship between the wood components and the structure and properties of the wood substrate was studied,and the electrocatalysts were prepared by loading catalytically active substances,and the effect of the wood substrate after adjusting the wood components on the catalytic performance of the composite electrocatalyst was further studied.This study is of great significance for the preparation of green and efficient wood-based electrocatalytic materials.