Computational design of novel MAX phase alloys for potential hydrogen storage media combining first principles and cluster expansion methods

TL;DR

This study uses first principles and cluster expansion methods to identify MAX phase alloys, especially Cu-doped Ti2AlC, with enhanced hydrogen storage capacity suitable for ambient conditions.

Contribution

It introduces a computational approach combining first principles and cluster expansion to design MAX phase alloys with improved hydrogen storage capabilities.

Findings

Ti-A layers favor hydrogen adsorption at tetrahedral sites.

Ti2CuC has the highest hydrogen adsorption energy among studied phases.

Doped Ti2AlxCu1-xC alloys can store up to 3.66 wt% hydrogen at ambient conditions.

Abstract

Finding a suitable material for hydrogen storage at ambient atmospheric conditions is challenging for material scientists and chemists. In this work, using a first principles based cluster expansion approach, the hydrogen storage capacity of Ti2AC (A = Al,Ti, Cr, Mn, Fe, Co, Ni, Cu, and Zn) MAX phase and its alloys were studied. We found that hydrogen is energetically stable in Ti-A layers in which the tetrahedral site consisting of one A atom and three Ti atoms is energetically more favorable for hydrogen adsorption than other sites in the Ti-A layer. Ti2CuC has the highest hydrogen adsorption energy than other Ti2AC phases. We find that 83.33% Cu doped Ti2AlxCu1-xC alloy structure is both energetically and dynamically stable and can store 3.66 wt% hydrogen at ambient atmospheric conditions, which is higher than both Ti2AlC and Ti2CuC phase. These findings indicate that the hydrogen capacity of the MAX phase can be significantly improved by doping an appropriate atom species.