Fabrication of MoO_x/Mo₂C-Layered Hybrid Structures by Direct Thermal Oxidation of Mo₂C

Abstract

Two-dimensional (2D) Mo2C, as a new member of transition metal carbides, has many intriguing properties and potential applications in superconductors and electronic devices. The thermal stability of 2D materials is essential for the performance of the related devices, especially the ones with a vertical heterostructure. However, rare reports have demonstrated the thermal stability of Mo2C and the effects of thermal stability on its performance. Here, we propose a facile and controllable method to directly oxidize Mo2C to MoO x , forming a MoO x /Mo2C heterostructure. During the oxidization process, an in situ technique is employed to uncover the transformation and thermal stability of the Mo2C. The chemical vapor deposition Mo2C shows high structural stability below 550 °C in Ar or below 350 °C in O2, which demonstrates the high thermal stability and antioxidation of the Mo2C film. The metallic Mo2C is gradually oxidized to semiconducting MoO x as the temperature increases above 350 °C. The oxidization rate can be easily controlled by adjusting the oxidation temperature and time. Further, the obtained MoO x /Mo2C vertical hybrid structure shows obvious Schottky junction behaviors, strongly indicating the perfect interfacial contact between the component layers. This work offers a new strategy for the controllable fabrication of high-quality 2D heterostructures.

Rational Design of Two-Dimensional Transition Metal Carbide/Nitride (MXene) Hybrids and Nanocomposites for Catalytic Energy Storage and Conversion

“…For instance, PC applications require semiconducting photo-absorbers, which can be formed via in-situ oxidation or hydro/solvothermal treatment of Ti-based MXenes. 89 In contrast, oxide formation on MXenes is detrimental to electrocatalysis, as oxides are less conductive and limit charge transport properties, 148 so a self-assembly process may be more appropriate. MXene hybrids should also be carefully designed to optimize chemical coupling at the MXene-secondary material interfaces toward catalytic activity enhancement.…”

“…This method was also employed to synthesize S-doped TiO2 NPs/C (Figure 7b) from S-doped Ti3C2Tx, whereby S doping further optimized H + binding energy for efficient HER. 97 The strategy of using MXenes as precursors to synthesize MXene/TM oxide hybrids has also been applied to other MXenes, given the relative ease in oxidizing MXenes, 192,193 such as in the oxidation of Nb2CTx to Nb2CTx/C/Nb2O5, 194 Mo2CTx to Mo2C/MoOx, 148 and V2CTx to V2CTx/V2Ox. 57,195 Apart from acting as TM oxide precursors, MXenes can also serve as efficient PC/PEC HER co-catalysts themselves to promote photo-generated charge carrier separation when coupled to semiconductors.…”

“…For this purpose, it is not unreasonable to use MXene-like surrogate structures that can be synthesized using bottom-up approaches with atomic precision (CVD and ALD) for such fundamental studies. 65,66,148 Finally, efforts can be undertaken in the development of mild and scalable top-down MXene synthesis and hybridization techniques to (1) minimize MXene oxidation and mechanical damage during processing especially at high temperatures, 192,193 (2) enable greater control over the chemical composition, morphology and distribution of the secondary material grown on MXenes, and (3) realize highly porous and 3D MXene hybrid networks for efficient mass and long-range charge transport to further enhance catalytic activity. 169 Given the rapid rise in interest amongst MXene hybrids and composites, we expect an increase in both experimental and theoretical efforts towards developing MXene hybrids for clean energy and related applications in the near future.…”

Mo-Based Layered Nanostructures for the Electrochemical Sensing of Biomolecules

“…The most recognized "top-down" method was the exfoliation technique, starting from three-dimensional layered materials in bulk. Figure 2 reports a composite picture showing some of these techniques for preparation, and examples of typical nanomaterials obtained [36]. A brief summary of these techniques of preparation, with special emphasis to 2D Mo-based materials, is reported below.…”

A Solvent‐Free Strategy to Synthesize MoS2/Mo2C‐Embedded, N, S Co‐Doped Mesoporous Carbon as Electrocatalysts for Hydrogen Evolution

“…[15,16] Furthermore, extensive synthetic methods have been reported, including controlling morphology and nanostructure, constructing hybrid structures, and introducing a second transition metal. [17,18] However, during these processes, solvent such as water, ethanol, and HCl solution are frequently applied in the process of preparation and posttreatment, most of which are harmful to the environment and increase the cost of final products. [19,20] However, to our knowledge, very limited studies about solvent free and solidstate synthesis strategy of the Mo, N, S co-doped mesoporous carbon have been reported.…”