Epitaxial synthesis of Ni-MoS2/Ti3C2Tx MXene heterostructures for hydrodesulfurization

Hierarchical structures of 2D layered Ti3C2Tx MXene hold potential for a range of applications. In this study, catalysts comprising few-layered MoS2 with Ti3C2Tx have been formulated for hydrodesulfurization (HDS). The support Ti3C2Tx was derived from MAX phases (Ti3AlC2) via a liquid-phase exfoliation process, while MoS2 was obtained from synthesized aqueous ammonium tetrathiomolybdate (ATM). Furthermore, a series of catalysts with different architectures was synthesized by confinement of ATM and/or the promoter Ni in Ti3C2Tx at different mole ratios, through a thermal conversion process. The synthesized MoS2/Ti3C2Tx and Ni-MoS2/Ti3C2Tx catalysts were characterized using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), high-resolution transmission electron microscopy (HRTEM), and temperature-programmed reduction (TPR) measurements. The number of MoS2 layers formed on the Ti3C2Tx support was calculated using Raman spectroscopy. The heterostructured few-layered MoS2/Ti3C2Tx catalysts were applied in sulfur removal efficiency experiments involving thiophene. The active MoS2 sites confined by the Ti3C2Tx enhanced hydrogen activation by proton saturation, and the electron charge stabilized the sulfur atom to facilitate hydrogenation reactions, leading to predominant formation of C-4 hydrocarbons. The Ni-MoS2/Ti3C2Tx showed the best activity at a promoter molar ratio of 0.3 when compared to the other catalysts. In particular, it is evident from the results that ATM and Ti3C2Tx are potential materials for the in situ fabrication of hierarchical few-layered MoS2/Ti3C2Tx catalysts for enhancing hydrodesulfurization activity in clean fuel production.