| Ti3C2Tx is a representative member of MXene,a new type of transition metal carbon/nitride two-dimensional materials that has emerged in recent years.In addition to the excellent electrical conductivity and large specific surface area as graphene,it has many other excellent physical and chemical properties such as good hydrophilicity and flexibility,adjustable surface functional group,making it an ideal electrode material for energy storage devices such as supercapacitors and secondary batteries.At present,Ti3C2Tx is mainly prepared by selective etching in hydrofluoric acid or fluorine-containing acidic solution,which has safety hazard and reduces the capacitance performance of the material due to the introduction of the-F terminal group which reduces the adsorption performance of the material.Aiming at the above problems,we take Ti3C2Tx of MXene as the research object and prepare Ti3C2Tx material by a novel alkaline etching hydrothermal method.The influence of etching parameters on the structure morphology and yield of the product was analyzed systematically,the electrochemical performance test and analysis of the three-electrode and two-electrode systems were carried out.Besides,by compounding with pseudocapacitors material FeOOH,the performance in Na2SO4 electrolyte was expected to improve.In this paper,The NaOH solution was used as an etchant to prepare Ti3C2Tx by a simple one-step hydrothermal etching of the precursor Ti3AIC2,in which high concentration NaOH and high reaction temperature are necessary for etching.By adjusting the hydrothermal parameters,High yield of Ti3C2Tx could be obtained under the parameters of 28 mol/L of NaOH concentration,280? of the heating temperature and 16 h of the reaction time.The morphological characterization result shows that the etched Ti3C2Tx has a complete morphological structure with an average lateral dimension of several ?m,an average layer spacing of about 1.2 nm and an atomic lattice spacing of 0.28 nm.The product does not contain any-F functional group,the structural characterization showes that the functional groups on the surface of Ti3C2Tx are mainly-O and-OH,corresponding to Ti-C-0 and Ti-C-OH.Thus in general,a high concentration of NaOH solution can successfully prepare Ti3C2Tx by etching the precursor Ti3AIC2 at a high temperature.For the prepared Ti3C2Tx supercapacitor electrode,the electrochemical performance test based on three-electrode system shows that Ti3C2Tx has good capacitance performance in 1 mol/L H2SO4 electrolyte.In the potential window of-0.5 V?-0.05 V,the CV curve under different sweep speeds maintains a similar shape and the galvanostatic charge-discharge curve keeps highly symmetrical like an isosceles triangle.The specific capacity at a current density at 1 A·g-1 reaches 279.3 F·g-1 and still maintains 140 F·g-1 at a large current density of 10 A·g-1,demonstrating its good rate performance.The capacitance retention keeps 82.3%after 5000 cycles at a current density of 2 A·g-1,demonstrating excellent cyclic stability of the material.Ti3C2Tx-based symmetric supercapacitors also exhibit high specific capacitance and low impedance under a potential window of 0 V?0.5 V in 1 mol/L H2SO4 electrolyte,indicating an application potential on devices.Study of Ti3C2Tx/FeOOH composites shows that FeOOH mainly exists in amorphous form.With a loading quantity of 70 mg on 100 mg Ti3C2Tx,FeOOH can uniformly attach on the surface and side of the Ti3C2Tx matrix in a small size.The results of three-electrode test show that the Ti3C2Tx/FeOOH composite has good capacitance performance in the potential window of-1 V?-0.1 V in 1 mol/L Na2SO4 electrolyte.When the current density is 1 A·g-1,the specific capacity reaches 242.4 F·g-1 The AC impedance spectrum also demonstrates that it has a low impedance and its cycling performance is better than pure FeOOH. |
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