Fabrication And Electrochemical Properties Of TiO₂ Nanowires/Graphene Composite Materials

With the global energy focus gradually shifting to clean,renewable new energy direction,the demand for more advanced energy storage devices has become increasingly strong.Therefore,the storage of new energy has become a very popular research direction.Supercapacitors have been widely studied because of their high power density,long cycle life and fast charging and discharging ability.The selection of electrode materials plays a decisive role in the performance of supercapacitors.The key to improve the performance of supercapacitors is to prepare a kind of electrode materials with low cost,good stability and high specific capacitance.TiO₂ has the characteristics of low cost,high electrochemical stability,large specific surface area and pseudocapacitance.However,due to the poor conductivity of TiO₂,it can not play a high capacitance performance.Graphene has very high conductivity and double-layer capacitance,but the charge storage capacity of double-layer capacitance is low.Therefore,this paper proposes a method to prepare one-dimensional TiO₂ nanowires?TiO₂ NWs?from TiO₂ nanoparticles?TiO₂ NPs?and to composite with graphene at the same time.A composite electrode material with high specific capacitance was obtained by synergistic effect of the two materials.Graphene oxide?GO?was prepared by a improved Hummers method.Then,the precursor of TiO₂ NWs-reduced graphene oxide?rGO?composite was prepared by hydrothermal method,using TiO₂ NPs and GO as raw materials at 200?for 24 h.Then the precursor was cleaned in HCl,and the TiO₂ NWs–rGO composite was obtained by annealing in Ar.In order to investigate the effect of mass ratio of TiO₂ NPs and GO on electrochemical performance,we prepared composite materials with different mass ratio,and then characterized their morphologies and structures by Scanning electron microscopy?SEM?,Raman spectroscopy?Raman?and X-ray diffraction?XRD?.In addition,cyclic voltammetry?CV?,galvanostatic charge-discharge?GCD?and electrochemical impedance spectroscopy?EIS?were performed in a three-electrode system using 6 M KOH as electrolyte.The results show that:after the composite of TiO₂ NPs and GO,the TiO₂ NPs formed one-dimensional nanowire structure,and GO was reduced to rGO.When the mass ratio of TiO₂ NPs to GO is 1:4,the electrochemical properties of the composite are the best.And the electrochemical properties of the composites with all ratios are better than those of the single TiO₂ NWs and the single rGO.At a current density of 1 A·g^-1,the specific capacitance of composites with a mass ratio of 1:4 is 572 F·g^-1,and the capacitance retention rate is 84%after 5000 cycles of galvanostatic charge-discharge at a current density of 10 A·g^-1.