(347b) Role of Dopants in Dehydrogenation of NaMgH3 Core-Shell Nanostructures

Authors: Fernando Soto¹, Daniela S. Mainardi²

¹Institute for Micro-manufacturing, Louisiana Tech University

²Institute for Micro-manufacturing, Chemical Engineering, Louisiana Tech University

Abstract

            NaMgH₃ is an attractive hydrogen storage material due to its 6 wt % hydrogen capacity and its hydrogenation/dehydrogenation reversibility. However, more fundamental understanding of the role of dopants to potentially improve the thermodynamics and kinetics of this hydride system is needed. Previous results show that clusters of hydrogen storage materials have a much lower desorption energy that their bulk counterparts; hence, they enable hydrogen desorption at lower temperatures².

            In our research group, the synergistic effects of 3d transition-metal co-dopants on the dehydrogenation kinetics and thermodynamics of NaMgH₃ have been studied using first-principles calculations based on density functional theory.  Results indicate that co-dopants introduced at the (001) NaMgH₃ surface model improves the reaction kinetics by lowering the Gibbs Free-Energy barriers. This indicates that NaMgH₃ is suitable for nano-structured modification by 3d- transition metal dopants.

            In this paper, 3d transition-metal doped NaMgH₃ nanoclusters with core-shell features are investigated using density functional theory to systematically explore their segregation energy, cohesive energy, substitutional doping energy, and hydrogen desorption energy to determine 3d transition metal core-shell preference. These calculations provide a general trend for nano-structured manipulation of hydride systems geared towards reducing the current high temperature hydrogen desorption barrier, and provide a more detailed understanding of dopant behavior.