Three-Dimensional Superhydrophobic Hollow Hemispherical MXene for Efficient Water-in-Oil Emulsions Separation.

Haoran Chen,Chunxiang Wei,Wei Yang,Weiming Meng,Dingding Wang,Hongdian Lu,Tao Li,Fanglin Chen,Riyuan Wang

doi:10.3390/nano11112866

Abstract

A superhydrophobic macroporous material composed of hollow hemispherical MXene (HSMX) was synthesized by the thermal annealing of MXene-wrapped cationic polystyrene spheres (CPS@MXene). Notably, the spherical MXene shells exhibited highly efficient catalysis of the carbonization of CPS into carbon nanoparticles. Their insertion into the interlayer of MXene increased the d-spacing and created hollow hemispheres. The as-prepared HSMX with nanoscale walls had a lower packing density than MXene, but higher porosity, total pore volume, and total pore area. Moreover, the stacking of hollow hemispheres promoted the formation of a highly undulating macroporous surface and significantly improved the surface roughness of the HSMX-based 3D membrane, resulting in superhydrophobicity with a water contact angle of 156.4° and a rolling angle of 6°. As a result, the membrane exhibited good separation efficiency and Flux for emulsifier-stabilized water-in-paraffin liquid emulsions, which was dependent on its superhydrophobic performance and strong demulsification ability derived from the razor effect originating from the ultrathin walls of HSMX. This work provides a facile approach for the transformation of highly hydrophilic 2D MXene into superhydrophobic 3D HSMX, and opens a new pathway for the development of advanced MXene-based materials for environmental remediation applications.

Highlights

A new class of graphene-like two dimensional (2D) crystalline transitionmetal carbides (MXenes), mainly in the form of Ti3 C2 Tx -MXene, has shown great prospects in various fields, including energy conversion and storage, and electromagnetic interference shielding, owing to their unique physicochemical properties [1,2,3,4]
After thermally evaporating Cationic polystyrene spheres (CPS) from CPS@MXene spheres, a honeycomb-like macroporous architecture composed of mostly hollow hemispherical MXene (HSMX) was obtained
This work demonstrates the fabrication of hollow hemispherical MXene (HSMX) by thermal annealing of CPS@MXene spheres via a sacrificial template approach

Summary

Introduction

A new class of graphene-like two dimensional (2D) crystalline transitionmetal carbides (MXenes), mainly in the form of Ti3 C2 Tx -MXene, has shown great prospects in various fields, including energy conversion and storage, and electromagnetic interference shielding, owing to their unique physicochemical properties [1,2,3,4]. It is known that 2D nanomaterials, including MXene, graphene, and clay, are prone to restacking when their corresponding nanosheets are peeled off owing to the intrinsic intermolecular forces, such as van der Waals forces and hydrogen bonding, which weaken their nanoscale dispersion and activities [12,13,14,15,16,17,18]. It is difficult to obtain a 3D MXene material directly from individual 2D nanosheets owing to the inherent characteristics of MXene. The template method is a simple and flexible approach to realize controllable and spatially well-defined 3D MXene materials prepared with various diameters, depending on the dimensions of the template used. The commonly used templates include ice [26], poly(methyl methacrylate)

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Conclusion