Enhanced hydrogen storage kinetics and air stability of nanoconfined NaAlH4 in graphene oxide framework

Abstract

With a growing concern over climate change, hydrogen offers a wide range of opportunities for decarbonization and provides a flexibility in overall energy systems. While hydrogen energy is already plugged into industrial sectors, a physical hydrogen storage system poses a formidable challenge, giving momentum for safe and efficient solid-state hydrogen storage. Accommodating such demands, sodium alanate (NaAlH₄) has been considered one of the candidate materials due to its high storage capacity. However, it requires a high temperature for hydrogen desorption and becomes inactive irreversibly upon air-exposure. To enhance sluggish reaction kinetics and reduce the hydrogen desorption temperature, NaAlH₄ can be confined into a porous nanoscaffold; however, nanoconfined NaAlH₄ with sufficient hydrogen storage performance and competent stability has not been demonstrated so far. In this work, we demonstrate a simultaneously enhanced hydrogen storage performance and air-stability for NaAlH₄ particles confined in a nanoporous graphene oxide framework (GOF). The structure of the GOF was elaborately optimized as a nanoscaffold, and NaAlH₄ was infiltrated into the pores of the GOF via incipient wetness impregnation. As a result of the nanoconfinement, both the onset temperature and activation energy for hydrogen desorption of NaAlH₄ are significantly decreased without transition metal catalysts, while simultaneously achieving the stability under ambient conditions.