Nanosizing Improves Hydrogen Storage

For hydrogen storage applications, materials composed of nanometer-sized particles outperform samples with larger particles in terms of energetics and hydrogen-release (desorption) temperature, according to researchers in the Netherlands (J. Am. Chem. Soc., DOI: 10.1021/ja710667v). The study may lead to new forms of materials that are well suited for use in hydrogen-powered automobiles. Slow hydrogen desorption kinetics and poor chemical reversibility limit the usefulness of widely studied hydrides, such as sodium alanate (NaAlH4), in hydrogen storage applications. Reducing particle size is one approach to improving those properties, but common methods lead to fairly large particles (150-nm diameters or larger) and broad size distributions. Cornelius P. Baldé, Krijn P. de Jong, and coworkers at Utrecht University developed wet synthesis methods that yield NaAlH₄ particles measuring 1–10 μm, 19–30 nm, and 2 –10 nm. Tests show that the hydrogen-release temperature and activation energy decrease from 186 ºC and 116 kJ/mol for the larger particles to 70 ºC and 58 kJ/mol for the smaller particles. In addition, reducing particle size lowers the pressure needed for recharging the material with hydrogen, the team says.