In Situ Growth of Interfacially Nanoengineered 2D-2D WS₂/Ti₃C₂T_x MXene for the Enhanced Performance of Hydrogen Evolution Reactions

In line with current research goals involving water splitting for hydrogen production, this work aims to develop a noble-metal-free electrocatalyst for a superior hydrogen evolution reaction (HER). A single-step interfacial activation of Ti₃C₂T_x MXene layers was employed by uniformly growing embedded WS₂ two-dimensional (2D) nanopetal-like sheets through a facile solvothermal method. We exploited the interactions between WS₂ nanopetals and Ti₃C₂T_x nanolayers to enhance HER performance. A much safer method was adopted to synthesize the base material, Ti₃C₂T_x MXene, by etching its MAX phase through mild in situ HF formation. Consequently, WS₂ nanopetals were grown between the MXene layers and on edges in a one-step solvothermal method, resulting in a 2D-2D nanocomposite with enhanced interactions between WS₂ and Ti₃C₂T_x MXene. The resulting 2D-2D nanocomposite was thoroughly characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses before being utilized as working electrodes for HER application. Among various loadings of WS₂ into MXene, the 5% WS₂-Ti₃C₂T_x MXene sample exhibited the best activity toward HER, with a low overpotential value of 66.0 mV at a current density of −10 mA cm^-2 in a 1 M KOH electrolyte and a remarkable Tafel slope of 46.7 mV·dec^-1. The intercalation of 2D WS₂ nanopetals enhances active sites for hydrogen adsorption, promotes charge transfer, and helps attain an electrochemical stability of 50 h, boosting HER reduction potential. Furthermore, theoretical calculations confirmed that 2D-2D interactions between 1T/2H-WS₂ and Ti₃C₂T_x MXene realign the active centers for HER, thereby reducing the overpotential barrier.