Ti4+ Substituted Magnesium Hydride as Promising Material for Hydrogen Storage and Photovoltaic Applications

TL;DR

This study uses first-principles calculations to explore Ti-substituted MgH2, revealing enhanced hydrogen storage properties and potential for improved photovoltaic efficiency due to intermediate band formation.

Contribution

It introduces Ti4+ substitution in MgH2 as a dual-purpose material for hydrogen storage and photovoltaic applications, supported by detailed electronic and bonding analyses.

Findings

Ti substitution reduces MgH2 stability, improving hydrogen storage.

Ti4+ substitution creates intermediate bands, enhancing solar cell efficiency.

Ti4+ substituted MgH2 shows promising optical and electronic properties for photovoltaics.

Abstract

In order to overcome the disadvantages of MgH2 towards its applications in on-board hydrogen storage, first principle calculations have been performed for Ti (2+, 3+, and 4+) substituted MgH2. Our calculated enthalpy of formation and H site energy implies that Ti substitution in Mg site reduces the stability of MgH2 which improve the hydrogen storage properties and Ti prefers to be in +4 oxidation state in MgH2. The bonding analyses through partial density of states, electron localization function and Bader charge of these systems confirm the existence of iono-covalent bonding. Electronic structure obtained from hybrid functional calculations show that intermediate bands (IB) are formed in Ti4+ substituted MgH2 which could improve the solar cell efficiencies due to multiple photon absorption from valence band to conduction band via IBs and converts low energy photons in the solar spectrum also into electricity. Further, our calculated carrier effective masses and optical absorption spectra show that Ti4+ substituted MgH2 is suitable for higher efficiency photovoltaic applications. Our results suggest that Ti4+ substituted MgH2 can be considered as a promising material for hydrogen storage as well as photovoltaic applications.