Strategies for the enhancement of heat storage materials performances for MgO/H2O/Mg(OH)2 chemical heat pump

Several strategies have been studied to maximize the performances of the storage medium and to increase Mg(OH)2 stability to several storage/release cycles. It is here proposed a deposition-precipitation (DP) method for growing Mg(OH)2 particles in aqueous medium on two types of carbon matrix, exfoliated graphite (EG) and carbon nanotubes (CNTs). At synthesis conditions, the carbon materials surface is negatively charged, being the pH at point of zero charge (pHPZC) lower than the pH of the solution, conversely Mg(OH)2 is positively charged (pHPZC higher than pH of the solution). As a result, an electrostatic interaction between the two materials occurs thus improving the stability of the composite under operating conditions. Compared to EG, CNTs, due to their morphology and physical properties, should provide a more efficient transport of water vapour and heat.