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

Abstract

Hierarchical structures of 2D layered Ti₃C₂T_x MXene hold potential for a range of applications. In this study, catalysts comprising few-layered MoS₂ with Ti₃C₂T_x have been formulated for hydrodesulfurization (HDS). The support Ti₃C₂T_x 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 Ti₃C₂T_x at different mole ratios, through a thermal conversion process. The synthesized MoS₂/Ti₃C₂T_x and Ni–MoS₂/Ti₃C₂T_x 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 Ti₃C₂T_x support was calculated using Raman spectroscopy. The heterostructured few-layered MoS₂/Ti₃C₂T_x catalysts were applied in sulfur removal efficiency experiments involving thiophene. The active MoS₂ sites confined by the Ti₃C₂T_x enhanced hydrogen activation by proton saturation, and the electron charge stabilized the sulfur atom to facilitate hydrogenation reactions, leading to predominant formation of C₄ hydrocarbons. The Ni–MoS₂/Ti₃C₂T_x 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 Ti₃C₂T_x are potential materials for the in situ fabrication of hierarchical few-layered MoS₂/Ti₃C₂T_x catalysts for enhancing hydrodesulfurization activity in clean fuel production.