Probing hydrogen storage through cation replacement in CaNiH3 for clean environment: A computational explaination

Abstract

Hydrogen as a fuel is more environmentally friendly than carbon fuel. It has the potential to reduce the effects of global warming, which is a direct consequence of fossil fuel consumption. Storing hydrogen fuel, however, is challenging as it is not transported as a gaseous state due to its low boiling point and highly explosive nature. Additionally, it occupies a large volume of space due to its lower density posing challenges while transporting. To study hydrogen storage properties of cubic (Pm-3m) CaNiH₃, we used first principle theory. The negative formation energy of the optimized structure indicates that the studied compound is thermodynamically stable and synthesizable whereas Born's stability calculations confirms the mechanical stability of the materials as well. By increasing the impurity (Mg) concentration, hydrogen gravimetric capacity increases from 2.884 wt% to 3.395 wt%. The calculated value of hydrogen storage reveals that MgNiH₃ is an excellent candidate for hydrogen storage applications. Several parameters such as second-order elastic constant, young modulus, shear modulus, Poisson ratio, sound velocities, and Deby temperature have been deliberated thoroughly. Pugh ratio reveals that Mg₁₁Ca_0·89NiH₃ and Mg_0·5Ca_0·5NiH₃ have a brittle nature as their $B/G<1.75$. The present compounds have a metallic nature, as their valence band and conduction band overlap with each other. The subject material is a vital addition towards energy storage materials for green and clean approach.