Exfoliation Energy as a Descriptor of MXenes Synthesizability and Surface Chemical Activity.

Daniel Dolz,Francesc Illas,Francesc Viñes,Ángel Morales-García

doi:10.3390/nano11010127

Abstract

MXenes are two-dimensional nanomaterials isolated from MAX phases by selective extraction of the A component—a p-block element. The MAX exfoliation energy, Eexf, is considered a chemical descriptor of the MXene synthesizability. Here, we show, by density functional theory (DFT) estimations of Eexf values for 486 different MAX phases, that Eexf decreases (i) when MAX is a nitride, (ii) when going along a metal M component d series, (iii) when going down a p-block A element group, and (iv) when having thicker MXenes. Furthermore, Eexf is found to bias, even to govern, the surface chemical activity, evaluated here on the CO2 adsorption strength, so that more unstable MXenes, displaying larger Eexf values, display a stronger attachment of species upon.

Highlights

Since their first isolation in 2011 [1], MXenes, a new family of two-dimensional (2D)layered materials, have constituted an incredibly growing hub of research on different fields of technology; from materials for Lithium batteries [2,3] to supercapacitors [4,5], electromagnetic interference shielding materials [6,7,8], and uses as heterogeneous catalysts [9,10,11]or biosensors [12,13], to name a few
Present by usingfunctional density functional theory (DFT) calculations onofa models, we show that such exfoliation energies are well-suited series of MXene and MAX models, we show that such exfoliation energies are descriptors of both the of MXenes synthesizability and of their activity, well‐suited descriptors both the MXenes synthesizability andsurface of theirchemical surface chemical exemplified here on the adsorption, and related to the 2 the CO2 adsorption, and related to 2 the CO2 abatement
Spurred by the successful employment of surfaces energies as physicochemical descriptors of a given surface chemical activity, we analyzed here whether exfoliation energies can be employed to predict the chemical activity of MXenes, which followed the fact that the bond strength between the p-block A element and the M early transition metal in a given MAX phase was found to be related to the easiness of MXene extraction

Summary

Introduction

Since their first isolation in 2011 [1], MXenes, a new family of two-dimensional (2D). A appealing field is the use of MXenes in environment-related applications, e.g., pristine MXenes, have been first theoretically [17] and later experimentally [18] appointed to be well-suited materials for carbon dioxide (CO2 ) greenhouse gas abatement, with CO2 uptakes an order of magnitude larger than other tested porous materials This paramount performance is due to the MXenes inherently enhanced chemical activity, arising from their intrinsic metastability. Many of the above applications imply the interaction of a given species with the MXene surface, the surface chemical activity being, a priori, a key feature In this line, surface energies, known as surface tensions, have been appointed as descriptors of the material’s chemical activity [22].

Computational Details

Results

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Trends of theofCO

Trends

Conclusions