Hierarchical graphene nanowalls/Ti, Mo-MXene nano compounds for enhanced electrocatalytic hydrogen evolution

In this study, hybrid Ti 3 C 2 T x and Mo 3 C 2 T x MXene nanosheets integrated with graphene nanowalls (GNWs) were synthesized using chemical vapor deposition (CVD) and thoroughly characterized for their electrocatalytic performance in the hydrogen evolution reaction (HER). Comprehensive characterization techniques, including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area analysis, and X-ray photoelectron spectroscopy (XPS), were employed to evaluate the structure, surface chemistry, and morphology of the composites. XPS analysis confirmed the successful removal of aluminum from the MAX phase, alongside the introduction of functional groups such as oxygen and fluorine, which are critical for enhancing HER efficiency. The GNWs/Mo 3 C 2 T x -MXene composite exhibited the lowest overpotential of 132 mV at 10 mA/cm 2 , significantly outperforming its pristine MAX and MXene counterparts. The Tafel slope for GNWs/Mo 3 C 2 T x -MXene was reduced to 178 mV/dec, compared to Mo-MXene (245 mV/dec), indicating improved reaction kinetics. The GNWs/Ti 3 C 2 T x -MXene composite demonstrated an overpotential of 359 mV and a Tafel slope of 242 mV/dec. Furthermore, Nyquist plots revealed low charge transfer resistance (R ct ) for both composites, correlating with enhanced electron transport. The composites also exhibited superior BET surface area and porosity, crucial for catalytic activity. These findings underscore the potential of GNWs/MXene hybrids as scalable, cost-effective alternatives to noble metal catalysts for HER. • GNWs/MXene hybrids synthesized by CVD show enhanced HER catalytic performance. • GNWs/Mo-MXene achieves 132 mV overpotential and 178 mV/dec Tafel slope. • GNWs prevent MXene restacking, boosting surface area and porosity. • GNWs/Mo-MXene shows lower charge transfer resistance and faster HER kinetics. • Scalable GNWs/MXenes offer a cost-effective alternative to noble metal catalysts.