Heat Capacity Studies of Nanoconfined Hydrogen

The effect of confinement on the thermodynamic properties and phase transitions of liquids and solids in confinement has been of long-standing interest and recent interest has focused on the effects of dimensionality. Hydrogen has been of interest due to the importance of quantum effects, in particular zero-point motion, and has been studied extensively in a variety of porous media. Templated porous materials, such as MCM-41, provide an attractive model system for studying the effects of confinement due to their highly uniform one-dimensional pores with variable pore size. Unfortunately, the minimum pore diameter is typically limited to a few nanometers which limits our ability to approach the one-dimensional limit. We will present measurements of adsorption isotherms and heat capacity of hydrogen confined in MCM-41. We will present the results for both bare MCM-41 and samples that have been preplated with noble gases to reduce the effective pore diameter