Surface adsorption in strontium chloride ammines

An adsorbed state and its implications on the ab-and desorption kinetics of ammonia in strontium chloride ammine is identified using a combination of ammonia absorption measurements, thermogravimetric analysis, and density functional theory calculations. During thermogravimetric analysis, ammonia desorption originating from the adsorbed state is directly observed below the bulk desorption temperature, as confirmed by density functional theory calculations. The desorption enthalpy of the adsorbed state of strontium chloride octa-ammine is determined with both techniques to be around 37-39 kJ/mol. A simple kinetic model is proposed that accounts for the absorption of ammonia through the adsorbed state. (C) 2013 AIP Publishing LLC.