Zinc substituted MgH_2 - a potential material for hydrogen storage applications

摘要

The search for efficient materials for onboard hydrogen storage applications is an emerging research field. Using density functional calculations, we demonstrate Zn substituted MgH2 as a potential material for hydrogen storage. We predicted the ground state crystal structure of ZnH2 which is found to be Pna2(1) (orthorhombic) structure with meta-stable behavior. The structural phase stability and phase transition of Mg1-xZnxH2 systems have been analyzed. The H site energy of Mg1-xZnxH2 systems is calculated to understand the hydrogen desorption process. Our calculations suggest that Zn substitution reduces the stability of MgH2, thereby it may reduce the decomposition temperature of MgH2. The band structure and density of states calculations reveal that the Mg1-xZnxH2 systems are insulators. The chemical bonding behavior of Mg1-xZnxH2 systems is established as iono-covalent in nature. Moreover, Zn substitution in MgH2 induces disproportionate Mg-H bonds which could also contribute the reduction in the decomposition temperature as well as H sorption kinetics. (C) 2019 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.