Newly developed hybrid materials made of magnesium hydroxide and carbon nanotubes were proposed as heat storage medium for MgO/H2O/Mg(OH)(2) chemical heat pumps. Samples were synthesized by deposition-precipitation method varying the Mg(OH)(2) load (32-52 wt.%) and the type of carbon nanotubes, pristine or functionalized. The performances of the synthesized materials were evaluated by thermogravimetric analysis, which simulates the chemical heat pump cycle. The presence of the carbonaceous material positively affected the reaction performances, so that the hybrid materials showed improved heat storage/output capacity and faster heat output rate compared to pure Mg(OH)(2). The functionalization treatment and a proper Mg(OH)(2) load were fundamental to better the dispersibility of Mg(OH)(2) into the carbon nanotubes bundles which in turn enhanced the thermochemical performance of the active material, fully exploiting for the first time its maximum potential heat storage capacity, that is similar to 1300 kJ/kg(Mg(OH)2), thus bringing the development of this technology to a level closer to its industrial application. (C) 2016 Elsevier Ltd. All rights reserved.