Mo₂C/graphene heterostructures: low temperature chemical vapor deposition on liquid bimetallic Sn–Cu and hydrogen evolution reaction electrocatalytic properties

Abstract

Thin 2D Mo2C/graphene vertical heterostructures have attracted significant attention due to their potential application as electrodes in the hydrogen evolution reaction (HER) and energy storage. A common drawback in the chemical vapor deposition synthesis of these structures is the demand for high temperature growth, which should be higher than the melting temperature of the metal catalyst. The most common metallic catalyst is Cu, which has a melting temperature of 1084 °C. Here, we report the growth of thin, ∼200 nm in thickness, semitransparent micrometer-sized Mo2C domains and Mo2C/graphene heterostructures at lower temperatures using liquid Sn–Cu alloys. No Sn-associated defects are observed, making the alloy an appealing growth substrate. Raman spectroscopy reveals the vertical interaction between graphene and Mo2C, as shown by the variation in the strain of the graphene film. The results demonstrate the capability to grow continuous nanometer-thin Mo2C films at temperatures as low as 880 °C, without sacrificing the growth rate. Mo2C films are proven to be efficient electrocatalysts for the HER. Moreover, we demonstrate the beneficial role of graphene overgrown on Mo2C in reducing the HER overpotential values, which is attributed to more efficient charge transfer kinetics, compared to pure Mo2C films.

MAX phase materials and MXenes as hydrogen barrier coatings

“…However, this elevated temperature is unacceptable for many applications which has led to recent studies using Cu alloy substrates such as Cu-Sn to lower the growth temperature. 9 In this work the effects of using a Ag-Cu alloy as a substrate for Mo 2 C synthesis by chemical vapor deposition were systematically analyzed. The results conclusively demonstrated that synthesis of Mo 2 C is controlled by Mo diffusion through the liquid alloy ( Figure 2).…”

Low Temperature Synthesis and Growth Model of Thin Mo2C Crystals on Indium

“…In order to lower the CVD growth temperature of Mo2C crystals, alloys have been used. For this purpose, Cahitoglu et al 15 used a liquid bimetallic Sn-Cu alloy instead of Cu foil and showed that Mo2C could grow at temperatures as low as 880 °C with sizes of μm in diameter and hundreds of nm in thickness. Sun et al 16 used Au and very recently, Young et al…”

Recent Advances in Transition Metal Carbide Electrocatalysts for Oxygen Evolution Reaction

“…In this way, the temperature demand could be reduced to 880 • C, compared with the usual 1084 • C, and the cost of energy decreased without sacrificing the quality of the Mo 2 C/graphene film. The electrocatalyst also exhibited a better result than the pure Mo 2 C [116]. As the synthetic method has been developed, Mo 2 C, which is proved to be an excellent catalyst for HER, might also become low-cost and efficient OER electrocatalyst.…”