LAUSR

Recently, 2D Mo2C has drawn remarkable interest owing to its high strength,1 hardness,2 good corrosion resistance at high temperatures,3 high chemical stability,4 catalytic activity5 and superconductivity6 which make it an important candidate material for various applications such as electrochemical batteries,7,8 supercapacitors,9,10 electromagnetic interference shielding,11,12 and hydrogen evaluation reactions.5 Not only for the uses in these applications but also to study the fundamentals (eg the relationship between the morphology and properties of 2D Mo2C at nanoscale), controlled synthesis (thickness, lateral size, defects) of these thin crystals is required. CVD has been a promising technique to achieve large area and high quality thin layers of Mo2C 3,13,22,14-21. In this method, Cu foil is placed on a Mo substrate and heated. At above the melting temperature of copper, hydrocarbon gas (CH4) is introduced into the system, so that the Mo atoms diffusing through the copper, meet carbon atoms at the surface and form Mo2C. 3 In this process, besides the classical CVD processing parameters such as reaction temperature23 and duration,14 copper thickness and CH4 flow rate play critical roles in the determination of the final Mo2C crystal thickness.13,14 Firstly, Cu thickness is important because it does not only act as a catalyst, but also as a valve or membrane, controlling the Mo supply for the formation of 2D Mo2C crystals. 13With Received: 3 January 2020 | Revised: 11 May 2020 | Accepted: 27 May 2020 DOI: 10.1111/jace.17317