Sodium Alanate Nanoparticles − Linking Size to Hydrogen Storage Properties

Abstract

Important limitations in the application of light metal hydrides for hydrogen storage are slow kinetics and poor reversibility. To alleviate these problems doping and ball-milling are commonly applied, for NaAlH₄ leading to particle sizes down to 150 nm. By wet-chemical synthesis we have prepared carbon nanofiber-supported NaAlH₄ with discrete particle size ranges of 1−10 µm, 19−30 nm, and 2−10 nm. The hydrogen desorption temperatures and activation energies decreased from 186 °C and 116 kJ·mol⁻¹ for the largest particles to 70 °C and 58 kJ·mol⁻¹ for the smallest particles. In addition, decreasing particle sizes lowered the pressures needed for reloading. This reported size-performance correlation for NaAlH₄ may guide hydrogen storage research for a wide range of nanostructured light (metal) hydrides.