Effect of Postetch Annealing Gas Composition on the Structural and Electrochemical Properties of Ti₂CT_x MXene Electrodes for Supercapacitor Applications

Abstract

Two-dimensional Ti2CT x MXene nanosheets were prepared by the selective etching of Al layer from Ti2AlC MAX phase using HF treatment. The MXene sheets retained the hexagonal symmetry of the parent Ti2AlC MAX phase. Effect of the postetch annealing ambient (Ar, N2, N2/H2, and air) on the structure and electrochemical properties of the MXene nanosheets was investigated in detail. After annealing in air, the MXene sheets exhibited variations in structure, morphology, and electrochemical properties as compared to HF treated MAX phase. In contrast, samples annealed in Ar, N2, and N2/H2 ambient retained their original morphology. However, a significant improvement in the supercapacitor performance is observed upon heat treatment in Ar, N2, and N2/H2 ambients. When used in symmetric two-electrode configuration, the MXene sample annealed in N2/H2 atmosphere exhibited the best capacitive performance with specific capacitance value (51 F/g at 1A/g) and high rate performance (86%). This improvement in the electrochemical performance of annealed samples is attributed to highest carbon content, and lowest fluorine content on the surface of the sample upon annealing, while retaining the original two-dimensional layered morphology and providing maximum access of aqueous electrolyte to the electrodes.

High-Voltage Symmetric Supercapacitor Based on 2D Titanium Carbide (MXene, Ti2CTx)/Carbon Nanosphere Composites in a Neutral Aqueous Electrolyte

“…The large amount of C-C and the O = C-O peaks may arise from hydrocarbons formed during the etching 80 remaining after washing or formed during oxidation. 6,24 The Ti 2p core level (Figure 7d) was fitted with five components which consist of two doublets (2p 3/2 and 2p 1/2 80,84,85 The Ti-C signal may be ascribed to Ti atoms coming from the interior and can also come from TiC 83 which was evidenced from the XRD results to be present as impurity in the original MAX phase material. Ti signals with oxidation states 2+ and 3+ indicate the formation of different mixed oxides and carboxides on the MXene surface.…”

“…Although the MXene materials do not possess such a high surface area as electric double-layer capacitor (EDLC) materials, 6,11,24,35,36 they are suggested to employ the energy storage through pseudocapacitive ion intercalation route giving rise to high capacitance and attractive electrochemical properties without the need for a high surface area.…”

Room Temperature Oxidation of Ti3C2MXene for Supercapacitor Electrodes

“…The Ti 2p core level is fitted with four doublets (Ti 2p 2p 3/2 -Ti 2p 1/2 ) with a fixed area ratio equal to 2:1 and doublet separation of 5.7 eV. 40 In Fig. 6a, the Ti 2p 3/2 components are detected at 454.4, 455.8, 457.1 and 458.6 eV, respectively.…”

Electronic properties and applications of MXenes: a theoretical review

“…Experimentally, MXenes have already found applications as transparent conductors [18][19][20], field effect transistors [21], supercapacitors [22][23][24], Li ion batteries [25,26], electromagnetic interface shielders [27], fillers in polymeric composites [28], hybrid nanocompositites [29], purifiers [30,31], dual-responsive surfaces [32], suitable substrates for dyes [33], catalysts [34,35], promising materials for methane storage [36], and photocatalysts for hydrogen production [37], as well as being ceramic biomaterials with high photothermal conversion efficiency for cancer therapy [38]. Theoretically, many applications have been proposed for MXenes in electronic [39][40][41][42][43], magnetic [44][45][46][47][48], optical [49,50], thermoelectric [51][52][53][54][55][56], and sensing devices [57], as well as being new potential materials for catalytic and photocatalytic reactions [58][59][60]…”