How to Assess the Relative Volume Change of Reversible Metal Hydrides Easily, Speedily and Concisely (Enough) with a Surprising Relevance for Clarifying Thermodynamic Tailoring Effects

A practical way for assessing the relative volume change of reversible metal hydrides upon hydrogenation, based on the van’t Hoff reaction parameters, is outlined. Hitherto computational methods can provide that information only at a much higher level of complexity. By that method, the open issue of assessing the minimum pressure for complete [AlH₄]-formation in Ti-doped NaAlH₄ is resolved and the nature of the additional reaction pathway in KH/Ti-co-doped NaAlH₄ elucidated. This work summarizes the essentials for the thermodynamic tailoring of metal hydrides in nine points and adds thus a central missing piece to the puzzle of understanding reversible chemical hydrogen storage in metal hydrides.