Synthesis And Characterization Of Transition Metal Silicates Derived From Bamboo Leaves Applied To Supercapacitors

Due to the rapid consumption of fossil fuels and the growing problems of environmental pollution and energy waste,the exploitation of clean,efficient and environmentally-friendly devices for energy storage has become a hot topic that attracts more and more attention.Supercapacitors have good cycle stability,rapid charge/discharge rate and long cycle life,so they can stand out among numerous energy storage devices.For the past few years,transition metal silicate materials have become a sort of hopeful electrode material because of their great abundance,low cost,and excellent electrochemical performance.Furthermore,biomass materials have attracted a lot of attention owing to their low cost,entensive sources,and three-dimensional porous connected structures.As a kind of biomass material,bamboo leaves are ubiquitous all over the world,and rich in carbon and silicon.This study uses bamboo leaves as the raw material to design and synthesize transition metal silicate materials through a simple in-situ hydrothermal method.We carried out SEM,TEM,XRD,FT-IR and Raman tests to explore and analyze the morphologies,structures and compositions of the as-obtained transition metal silicates,and their electrochemical properies were assessed through a series of electrochemical tests.The results are as follows:Taking bamboo leaves as the raw material,the C/SiO₂ precursor was obtained by calcination,and CoNiSi/C composites were prepared through a simple hydrothermal method by using this precursor as the template.As a kind of single electrode material,the capacitance of CoNiSi/C was 226 F·g^-1at 0.5 A·g^-1,and the capacitance retention rate could reach up to 99%after 10000 cycles.The asymmetric device assembled from CoNiSi/C and Ni(OH)₂ presented the capacitance of 254 m F·cm^-2 at 2 m A·cm^-2,and the energy density of the device could reach0.79 Wh·m^-2at 3.75 W·m^-2.Using bamboo leaves as the raw material,the SiO₂ precursor was obtained by water bath heating and calcination.MSi(M=Ni,Co,Mn)silicates were synthesized through a simple one-step hydrothermal method by using this precursor as the template.The as-obtained MSi silicates were then etched through a strong alkali etching method to obtain e-MSi(M=Ni,Co,Mn)silicates.Employing e-MSi(M=Ni,Co,Mn)silicates as single electrode materials,e-Mn Si presented the best electrochemical properities,the capacitance of which was 439 F·g^-1at0.5 A·g^-1.Asymmetric devices were fabricated from e-MSi(M=Ni,Co,Mn)and activated carbon(AC),and e-Ni Si//AC presented the most excellent electrochemical performance.The specific capacitance of e-Ni Si//AC device was 412 m F·cm^-2 at 4 m A·cm^-2,and the energy density of the device could reach 3.2 Wh·m^-2at 3.75 W·m^-2.Taking bamboo leaves as the raw material,the C/SiO₂ precursor was obtained by calcination in a tube furnace,and C/FeSi composites were successfully prepared through a facile one-step hydrothermal method by using this precursor as the template.As a kind of single electrode material,the capacitance of C/FeSi was 421 F·g^-1at 0.5 A·g^-1.Taking bamboo leaves as the raw material,the SiO₂ precursor was obtained by calcination in a muffle furance,and CoNiSi composites were successfully prepared through a simple one-step hydrothermal method by using this precursor as the template.As a kind of single electrode material,the specific capacitance of CoNiSi was 368 F·g^-1at 0.5 A·g^-1.The asymmetric device fabricated from C/FeSi and CoNiSi presented the capacitance of 492 m F·cm^-2 at 4 m A·cm^-2,and the energy density of the device could reach 0.79 Wh·m^-2at 3.75 W·m^-2.In summary,this paper use bamboo leaves as the raw material to design and synthesize transition metal silicate materials applied to supercapacitors through calcination and in-situ hydrothermal methods,and several kinds of electrode materials with high performance were successfully prepared.More importantly,this work provides a novel and feasible thread to prepare transition metal silicate materials applied to energy storage by using natural biomass rich in silicon.