MnCl2-MnBr2: New tailored sorbents for thermal transformation, heat pumps and thermochemical storage

This paper introduces a novel binary salt mixture for use in thermal transformation, heat pumping, and thermal energy storage cycles. Samples were manufactured using the wet impregnation technique, with the large temperature jump (LTJ) technique used to analyse MnBr₂ and MnCl₂ reactions with ammonia, revealing equilibrium lines with hysteresis. Thermogravimetric analysis (TGA) demonstrates that binary salt mixtures of MnBr₂ and MnCl₂ exhibit sorption characteristics distinct from their individual salts. Varying the molar ratios in the mixtures shows that MnCl₂-rich mixtures behave like pure MnCl₂, while MnBr₂-dominant mixtures resemble pure MnBr₂. The unique behaviour of these mixtures, with reaction profiles spanning a wide temperature range, suggests the formation of a new molecular structure. This broadens the operational temperature range of sorption technologies by up to 30 °C, emphasising the potential of engineered anion halide salt mixtures in heat pumping and thermal energy storage applications. • Large temperature jump technique characterised MnBr₂-NH₃ and MnCl₂-NH₃ sorption reactions. • Samples with MnCl₂:MnBr₂ molar ratios of 1:3, 1:1, and 3:1 were prepared and analyzed via TGA. • Results revealed new compounds with sorption properties dependent on the molar ratios of the salts. • Anion salt mixture “bands” extend the operational temperature range of single salts for sorption cycles and thermal storage.