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Contacting MoS₂ to MXene: Vanishing p-Type Schottky Barrier and Enhanced Hydrogen Evolution Catalysis

You, Jinxuan, Si, Chen, Zhou, Jian, Sun, Zhimei
Journal of physical chemistry 2019 v.123 no.6 pp. 3719-3726
carbides, catalysts, catalytic activity, hydrogen, hydrogen production, ionization, molybdenum disulfide, nanosheets, nitrides, physical chemistry, semiconductors
It is a big challenge to make a Schottky-barrier (SB)-free hole contact to MoS₂ with a high ionization of ∼6.0 eV. Here, using first-principles calculations, in a recently discovered large family of two-dimensional transition metal carbides or nitrides (MXenes), we have found six materials (V₂CO₂, Cr₂CO₂, Mo₂CO₂, V₄C₃O₂, Cr₂NO₂, and V₂NO₂) that can be used as metal contacts to monolayer MoS₂ with vanishing p-type Schottky barriers at contacting interfaces, resulting in highly efficient hole injection into MoS₂. We reveal that the successful achievements of the SB-free hole contacts at these MoS₂/MXene interfaces depend on not only the high work functions of the MXenes but also the absence of the formation of interfacial gap states that usually result in strong Fermi level pinning in the midgap of a semiconductor. We further propose that efficient charge injection into MoS₂ facilitated by SB-free contact could also increase the hydrogen evolution reaction (HER) activity of the 2H-MoS₂ basal plane by improving its conductivity as well as its ability to adsorb hydrogen. Not only are these findings invaluable for designing high-performance MoS₂-based electronic devices but they provide an effective route to optimize MoS₂ nanosheet catalysts for the HER.