Interfacial charge transfer and interaction in the MXene/TiO2 heterostructures

TL;DR

This study uses first principles calculations to explore how different surface terminations of MXene/TiO2 heterostructures affect interfacial charge transfer, adhesion, and electronic properties, informing energy storage material design.

Contribution

It provides detailed insights into the interfacial structure and energetics of MXene/TiO2 heterostructures, highlighting the impact of surface chemistry on charge transfer and adhesion.

Findings

OH-terminated MXene shows the largest charge transfer (~0.9 e/nm2) to TiO2.

Strong interfacial adhesion correlates with hydrogen bond formation.

Surface chemistry critically influences charge transfer and adhesion in heterostructures.

Abstract

Hybrid materials of MXenes (2D carbides and nitrides) and transition-metal oxides (TMOs) have shown great promise in electrical energy storage and 2D heterostructures have been proposed as the next-generation electrode materials to expand the limits of current technology. Here we use first principles density functional theory to investigate the interfacial structure, energetics, and electronic properties of the heterostructures of MXenes (Tin+1CnT2; T=terminal groups) and anatase TiO2. We find that the greatest work-function differences are between OH-terminated-MXene (1.6 eV) and anatase TiO2(101) (6.4 eV), resulting in the largest interfacial electron transfer (~0.9 e/nm2 across the interface) from MXene to the TiO2 layer. This interface also has the strongest adhesion and further strengthened by hydrogen bond formation. For O-, F-, or mixed O-/F- terminated Tin+1Cn MXenes, electron transfer is minimal and interfacial adhesion is weak for their heterostructures with TiO2. The strong dependence of the interfacial properties of the MXene/TiO2 heterostructures on the surface chemistry of the MXenes will be useful to tune the heterostructures for electric-energy-storage applications.