(574a) Hierarchical “Nanoroll” like MoS2/Ti3C2Tx Hybrid with High Electrocatalytic Hydrogen Evolution Activity

Hydrogen evolution reaction (HER) is an efficient fossil fuel-free path to produce hydrogen, which is an attractive energy carrier to address the global environmental and energy crisis. Platinum (Pt)-based catalysts show brilliant catalytic performance for HER, but the high cost and scarcity severely limit their pervasive application. Molybdenum disulfide (MoS₂) is one of the most promising candidates, because its hydrogen adsorption free energy (ΔGH) is near the optimal value of 0 eV. The HER activity of MoS₂ is mainly derived from the edge sites, despite the possible contribution from the vacancies in the basal plane. Therefore, exposing more edge sites is an effective strategy to enhance the catalytic activity of MoS₂. The electrocatalytic performance of the MoS₂ is also determined by some kinetic factors, especially the electron transport between the MoS₂ and electrolyte. Therefore, conductive additives or supports, such as conductive carbon and graphene, are usually introduced to reduce the resistive loss and enhance the catalytic activity. Two-dimensional (2D) MXenes, such as Ti₃C₂T_x (T_x de-notes surface functionalization, such as −O, −OH, and −F), is a new member of 2D materials. They show distinguished characteristics from graphene, such as the combination of hydrophilic surfaces and good electrical conductivity. Therefore, it may be used as a promising support to disperse catalysts. Meanwhile, MXenes has attracted much attention for HER reaction. Here, we report a simple strategy to synthesize the hierarchical “nanoroll” like MoS₂/Ti₃C₂T_x hybrid by combining liquid nitrogen-freezing and subsequent annealing. The quick freezing of the Ti₃C₂T_x nanosheets and ammonium tetrathiomolybdate mixture causes a sudden change in the strain of Ti₃C₂T_x, which leads to an interesting “nanoroll” like hierarchical structure. After annealing at H₂/Ar atmosphere, vertically aligned molybdenum sulfide (MoS₂) crystallites are in situ formed in and on the nanoroll like Ti₃C₂T_x. Notably, this hierarchical MoS₂/Ti₃C₂T_x hybrid exhibits excellent HER catalytic activity with a small onset overpotential of 30 mV, and a more than 25-fold increase in the exchange current density compared with MoS₂ was observed. The methods described here may be applicable to the preparation of other MXene-based hybrids with novel hierarchical structures for a variety of applications.