Synthesis of Cl@Ti3C2 for supercapacitor applications and first-principles insights into its enhanced electrochemical properties

Abstract

In this work, we examine the characteristics of Cl@Ti₃C₂ employing a first-principles approach to assess its suitability for supercapacitor applications. Structural investigations by scanning electron microscopy (SEM) confirm that tiny granules adhered to Cl@Ti₃C₂'s layers, in contrast to the layered morphology of Ti₃C₂ MXenes. Energy-dispersive X-ray spectroscopy (EDX) substantiates the presence of Ti, C and Cl elements in Cl@Ti₃C₂. Fourier transform infrared (FTIR) spectroscopy affirms the presence of C–Cl, –OH, C–C and CC bonds on the Cl@Ti₃C₂ surface, which further substantiates the EDX findings. The hexagonal crystalline structure persists even after the addition of Cl in the composite material according to X-ray diffraction (XRD) patterns. Cyclic voltammetry (CV) indicates the presence of redox peaks, endorsing pseudocapacitive behaviour. Additionally, galvanostatic charge–discharge (GCD) measurements yield a calculated capacitance of 695 F g⁻¹ for the fabricated (Cl@Ti₃C₂) electrode, with a power of 2506 W kg⁻¹ and an energy density of 55 Wh kg⁻¹ while exhibiting 98% cycle efficiency up to 5000 cycles. Electrochemical impedance spectroscopy (EIS) substantiates low impedance resulting from the adequate adsorption/desorption of cations by Cl@Ti₃C₂. Furthermore, electrochemical outcomes are validated by density functional theory (DFT) estimations to gain an understanding of the electronic density of states and charge transfer mechanisms near the Fermi level. The density of state (DOS) analysis demonstrates that the p-orbitals of Cl and the d-orbitals of Ti play an essential role as the primary facilitator of electron mobility across the Fermi level. The DFT computations and electrochemical results corroborate each other, further strengthening our findings of improved supercapacitor performance.