Enhancement of the selectivity of MXenes (M 2 C, M = Ti, V, Nb, Mo) via oxygen-functionalization: promising materials for gas-sensing and -separation

• Published in: Physical chemistry chemical physics : PCCP 2018, Vol.20 (9), p.6073-6082
• Main Authors: Junkaew, A, Arróyave, R
• Format: Article
• Language: English
• Subjects: Adsorption; Ammonia; Catalysis; Chemisorption; Density functional theory; Flue gas; Gas streams; Gases; Materials selection; Molybdenum; MXenes; Oxygen; Reactivity; Selectivity; Separation; Structural stability; Substrates; Titanium; Vanadium
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp08622a

Two-dimensional graphene-like materials, namely MXenes, have been proposed as potential materials for various applications. In this work, the reactivity and selectivity of four MXenes (i.e. M C (M = Ti, V, Nb, Mo)) and their oxygen-functionalized forms (i.e. O-MXenes or M CO ) toward gas molecules were investigated by using the plane wave-based Density Functional Theory (DFT) calculations. Small gas molecules, which are commonly found in flue gas streams, are considered herein. Our results demonstrated that MXenes are very reactive. Chemisorption is a predominant process for gas adsorption on MXenes. Simultaneously dissociative adsorption can be observed in most cases. The high reactivity of their non-functionalized surface is attractive for catalytic applications. In contrast, their reactivity is reduced, but the selectivity is improved upon oxygen functionalization. Mo CO and V CO present good selectivity toward NO molecules, while Nb CO and Ti CO show good selectivity toward NH . The electronic charge properties explain the nature of the substrates and also interactions between them and the adsorbed gases. Our results indicated that O-MXenes are potential materials for gas-separation/capture, -storage, -sensing, etc. Furthermore, their structural stability and SO -tolerant nature are attractive properties for using them in a wide range of applications. Our finding provides good information to narrow down the choices of materials to be tested in future experimental work.