Thermodynamic efficiencies of hydrogen storage processes using carbazole-based compounds

Carbazole-based compounds are promising candidates for hydrogen storage materials, and recent research has focused on finding components with higher hydrogen storage capacity and desirable physical properties. In this paper, thermodynamic efficiencies of hydrogenation and dehydrogenation reactions were analyzed assuming an idealized process. The physical properties and thermodynamic efficiencies of three carbazole-based compounds (n-ethylcarbazole, n-propylcarbazole, n-acetylcarbazole) were investigated for use as liquid organic hydrogen carriers (LOHCs). Unavailable physical and thermodynamic properties were estimated using molecular modeling or group-contribution methods. Process simulations were performed for hydrogen storage and release processes using a commercial simulation package to evaluate the thermodynamic efficiencies of three candidate molecules. Even though there might be additional loss of exergy upon practical implementation of the whole process, the framework developed in this study can be useful for screening candidate LOHC molecules.