MgO/H2O/Mg(OH)(2) chemical heat storage of waste energy from industrial processes is a promising technology in view of a more efficient use and saving of primary energy sources. A new approach was used to develop a hybrid heat storage material made of magnesium hydroxide (Mg(OH)(2)) and exfoliated graphite (which is used to improve the heat transfer with its high thermal conductivity). Mg(OH)(2) nanoplatelets were directly grown on graphite surface via a deposition-precipitation method to increase the compatibility between the two materials. The material thus obtained, named DP-MG, was experimentally tested to determine its heat storage and output capacities. An improvement of the material efficiency was obtained with a higher storage capacity at lower reaction temperature and a higher heat output rate. (C) 2015 Elsevier Ltd. All rights reserved.