Solid solution barium–strontium chlorides with tunable ammonia desorption properties and superior storage capacity

• Solid solutions of strontium and barium chloride were synthesized by spray drying.
• Adjusting molar ratios led to different crystallographic phases and compositions.
• Different molar ratios led to different ammonia ab-/desorption properties.
• 35–50 mol% BaCl2 in SrCl2 yields higher ammonia density than any other metal halide.
• DFT calculations can be used to predict properties of the mixtures.

Metal halide ammines are very attractive materials for ammonia absorption and storage—applications where the practically accessible or usable gravimetric and volumetric storage densities are of critical importance. Here we present, that by combining advanced computational materials prediction with spray drying and in situ thermogravimetric and structural characterization, we synthesize a range of new, stable barium-strontium chloride solid solutions with superior ammonia storage densities. By tuning the barium/strontium ratio, different crystallographic phases and compositions can be obtained with different ammonia ab- and desorption properties. In particular it is shown, that in the molar range of 35–50% barium and 65–50% strontium, stable materials can be produced with a practically usable ammonia density (both volumetric and gravimetric) that is higher than any of the pure metal halides, and with a practically accessible volumetric ammonia densities in excess of 99% of liquid ammonia.

Thermal desorption curves of ammonia from BaxSr(1−x)Cl2 mixtures with x equal to 0.125, 0.25 and 0.5 and atomic structure of Sr(NH3)8Cl2.Figure optionsDownload as PowerPoint slide