Lithium hydroxide monohydrate based thermochemical heat storage materials were modified with in situ formed 3D-nickel-carbon nanotubes (Ni-CNTs). The nanoscale (5-15 nm) LiOH·H2O particles were well dispersed in the composite formed with Ni-CNTs. These composite materials exhibited improved heat storage capacity, thermal conductivity, and hydration rate owing to hydrogen bonding between H2O and hydrophilic groups on the surface of Ni-CNTs, as concluded from combined results of in situ DRIFT spectroscopy and heat storage performance test. The introduction of 3D-carbon nanomaterials leads to a considerable decrease in the activation energy for the thermochemical reaction process. This phenomenon is probably due to Ni-CNTs providing an efficient hydrophilic reaction interface and exhibiting a surface effect on the hydration reaction. Among the thermochemical materials, Ni-CNTs-LiOH·H2O-1 showed the lowest activation energy (23.3 kJ mol-1), the highest thermal conductivity (3.78 W m-1 K-1) and the highest heat storage density (3935 kJ kg-1), which is 5.9 times higher than that of pure lithium hydroxide after the same hydration time. The heat storage density and the thermal conductivity of Ni-CNTs-LiOH·H2O are much higher than 1D MWCNTs and 2D graphene oxide modified LiOH·H2O. The selection of 3D carbon nanoadditives that formed part of the chemical heat storage materials is a very efficient way to enhance comprehensive performance of heat storage activity components.
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