Ti-enhanced kinetics of hydrogen absorption and desorption on NaAlH4 surfaces

TL;DR

This study uses first-principles calculations to show that Ti doping significantly improves hydrogen absorption and desorption kinetics in NaAlH4 by facilitating key reaction steps and stabilizing vacancies.

Contribution

It demonstrates that Ti dopants enhance hydrogen reaction kinetics in NaAlH4 by lowering energy barriers and stabilizing vacancies, providing insights for improved hydrogen storage materials.

Findings

Ti facilitates H2 dissociation and H atom adsorption.

Ti doping lowers energy barriers for H vacancy formation.

Ti brings energetically similar steps in hydrogen absorption/desorption.

Abstract

We report a first-principles study of the energetics of hydrogen absorption and desorption (i.e. H-vacancy formation) on pure and Ti-doped sodium alanate (NaAlH4) surfaces. We find that the Ti atom facilitates the dissociation of H2 molecules as well as the adsorption of H atoms. In addition, the dopant makes it energetically more favorable to creat H vacancies by saturating Al dangling bonds. Interestingly, our results show that the Ti dopant brings close in energy all the steps presumably involved in the absorption and desorption of hydrogen, thus facilitating both and enhancing the reaction kinetics of the alanates. We also discuss the possibility of using other light transition metals (Sc, V, and Cr) as dopants.