The Improvement in Hydrogen Storage Performance of MgH2 Enabled by Multilayer Ti3C2.

Zhaojie Wu,Jianhua Fang,Linglan Kong,Jiang Wu,Na Liu

doi:10.3390/mi12101190

Abstract

MgH2 has become a hot spot in the research of hydrogen storage materials, due to its high theoretical hydrogen storage capacity. However, the poor kinetics and thermodynamic properties of hydrogen absorption and desorption seriously hinder the development of this material. Ti-based materials can lead to good effects in terms of reducing the temperature of MgH2 in hydrogen absorption and desorption. MXene is a novel two-dimensional transition metal carbide or carbonitride similar in structure to graphene. Ti3C2 is one of the earliest and most widely used MXenes. Single-layer Ti3C2 can only exist in solution; in comparison, multilayer Ti3C2 (ML-Ti3C2) also exists as a solid powder. Thus, ML-Ti3C2 can be easily composited with MgH2. The MgH2+ML-Ti3C2 composite hydrogen storage system was successfully synthesized by ball milling. The experimental results show that the initial desorption temperature of MgH2-6 wt.% ML-Ti3C2 is reduced to 142 °C with a capacity of 6.56 wt.%. The Ea of hydrogen desorption in the MgH2-6 wt.% ML-Ti3C2 hydrogen storage system is approximately 99 kJ/mol, which is 35.3% lower than that of pristine MgH2. The enhancement of kinetics in hydrogen absorption and desorption by ML-Ti3C2 can be attributed to two synergistic effects: one is that Ti facilitates the easier dissociation or recombination of hydrogen molecules, while the other is that electron transfer generated by multivalent Ti promotes the easier conversion of hydrogen. These findings help to guide the hydrogen storage properties of metal hydrides doped with MXene.

Highlights

IntroductionAs an ideal secondary energy source, hydrogen energy shows many outstanding advantages, such as a high energy density of 142 MJ/kg [1], a wide range of potential sources, light weight, and environmental friendliness
The best performance of MgH2 -x wt.% ML-Ti3 C2 composite hydrogen storage materials prepared with different addition ratios reached an initial desorption temperature of 142 ◦ C with a desorption amount of 6.56 wt.%, which is 125 ◦ C lower than the initial desorption temperature of pristine MgH2
Outstanding hydrogen absorption and desorption performance indicates that the two-dimensional structure similar to that of graphene generates a large number of active sites and a high specific surface area, effectively facilitating the transport and diffusion of hydrogen in the system

Summary

Introduction

As an ideal secondary energy source, hydrogen energy shows many outstanding advantages, such as a high energy density of 142 MJ/kg [1], a wide range of potential sources, light weight, and environmental friendliness

Methods

Results

Conclusion