Study Of Preparation,adsorption And Electrochemical Properties Of Silica/graphene Oxide Composite Aerogel

Silica aerogel and silicon-based electrode materials are two typical silicon-based materials,which have broad application prospects in the fields of adsorption,catalysis,energy and biomedicine.As one of the important chemical materials,the texture properties of silicon-based materials play a decisive role in its application in the field of adsorption and energy.In this paper,a porous SiO2/GO composite aerogel was successfully prepared by supercritical drying of graphene oxide colloid and tetraethyl orthosilicate sol-gel method.Porous Si/SiO2/GO composites were successfully prepared by reducing SiO2/GO aerogel with magnesium powder.The structure and surface chemical state of SiO2/GO composite aerogels were analyzed by means of infrared and low-temperature nitrogen adsorption.The composite aerogel has low density(0.115g/cm3),low shrinkage(4%)and high porosity(94.7%).The specific surface area and pore volume are up to 909 m2/g and 5 cm3/g,respectively.The addition increases the thermal stability of the composite and increases the weight loss temperature by 50?.The existence of a porous structure and many hydrophobic surface groups makes the composite aerogel getting an uneven surface energy distribution and numerous energy peaks.The kinetic analysis indicated that the adsorption process of the cationic dye methylene blue was controlled by the initial stage of adsorption,which was fitting with the pseudo first-order kinetic model,whereas the thermodynamic isotherm adsorption process is more fitting with the Langmuir model.The sample with large specific surface area,large pore volume and many energy peaks would have good adsorption capacity.Langmuir equation give the best theoretical adsorption capacity being 190.9 mg/g for MB.The structure of Si/SiO2/GO composites was analyzed by means of scanning electron microscopy and X-ray diffraction.The Si/SiO2/GO composite has a three-dimensional structure in which particles and sheets are stacked together,and the surface of the particles is rough and the size is below 50 nm.The presence of GO inhibits the structural damage caused by the high temperature reaction.The specific surface area of the reduced sample is up to 420 m2/g,which is only 23%lower than the corresponding aerogel sample,and the porous network of the original aerogel is retained to some extent.The Si/SiO2/GO composite exhibits good electrochemical behavior.When charged and discharged at 0.1 A·g-1,the discharge capacity and charge capacity of the first ring are 1294 mAh·g-1 and 716 mAh·g-1,respectively.The cycle coulomb efficiency is 55%.The reversible capacity after 100 cycles was 559 mAh·g-1,and the capacity retention rate was 80%.The rate test showed that when the current density returned to 0.1 A·g-1,the reversible capacity of each sample could still return to the original 80%or more.When the charge-discharge current density is 1 A·g-1,the specific capacity of the half-cell is 411 mAh·g-1,which is higher than the theoretical capacity of graphite of 372 mAh·g-1.These good lithium storage properties are mainly attributed to good three-dimensional porous network characteristics.