Structural, Morphological, Optical and Electrochemical Study of Er-Intercalated V2CTx and Ti3C2Tx MXenes for Energy Conversion Applications

Abstract

Two-dimensional (2D) MXenes, also referred to as transition metal carbides/nitrides, exhibit electrocatalytic water-splitting applications due to their unique characteristics. These include a layered structure, high density, metallic-like conductivity, and functional surface groups that help to achieve efficient water splitting for the generation of clean and sustainable hydrogen energy. This study presents a comprehensive experimental investigation focusing on two different MXenes namely, V2CTx and Ti3C2Tx, and their corresponding nanocomposites, Er@V2CTx and Er@Ti3C2Tx, for their suitability for water-splitting applications. The electrochemical behaviour of the Er@V2CTx and Er@Ti3C2Tx nanocomposites, with varying percentages of Er incorporated into vanadium carbide and titanium carbide MXene matrices, is extensively studied and discussed. Electrochemical testing was conducted in an alkaline medium (1M KOH) to evaluate hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) potential. The Er@V2CTx nanocomposite exhibited a redox potential of 174 mV at a current density of 10 mA/cm2, with a Tafel slope of 107 mV/dec for HER. Similarly, the Er@Ti3C2Tx nanocomposite demonstrated an overpotential of 256 mV at 10 mA/cm2 current density, with a Tafel slope of 102 mV/dec for HER. For the OER, the Er@V2CTx nanocomposite exhibited an overpotential of 370 mV at 10 mA/cm2 current density, with a Tafel slope of 131 mV/dec, while the Er@Ti3C2Tx nanocomposite showed an overpotential of 381 mV at 10 mA/cm2 current density, with a Tafel slope of 157 mV/dec. The structure and morphology of the compounds were examined using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy, confirming the successful formation of the nanocomposites while retaining the desirable two-dimensional (2D) structure of MXene.