Thermodynamic analysis of hydrogen storage: Biphenyl as affordable liquid organic hydrogen carrier (LOHC)

One of the promising directions for accumulating hydrogen is its binding into a liquid organic hydrogen carrier (LOHC). In this concept, a LOHC is loaded with hydrogen (hydrogenation) during production and then discharged again (dehydrogenation) when the hydrogen is needed. Biphenyl is an interesting option as potential LOHC due to its reasonable storage capacity. This paper deals with the experimental chemical equilibrium study and a detailed analysis of the biphenyl hydrogenation reactions. We evaluated the consistent set of vapour pressures and standard molar thermodynamic properties of biphenyl derivatives with help of complementary vapour pressure measurements, and empirical and quantum-chemical calculations. The chemical equilibrium constants of hydrogenation-dehydrogenation and thermodynamic characteristics for the biphenyl system were determined.