Optimization of magnesium hydroxide composite material mixed with expanded graphite and calcium chloride for chemical heat pumps

► The expanded graphite (EG) mixture was developed for MgO/H2O chemical heat pump. ► The optimization of mixing weight ratio between EG and Mg(OH)2 was conducted. ► The dehydration rate of EG mixture increased as the mixing weight ratio decreased. ► A multiplied factor was introduced to decide the optimized mixing weight ratio. ► Optimized EG mixture shows better performance on dehydration than pure Mg(OH)2.