Diphenyl Ether Derivatives as Potential Liquid Organic Hydrogen Carriers: Thermochemical and Computational Study

Abstract

The liquid organic hydrogen carriers (LOHCs) are promising materials for hydrogen storage. The standard molar enthalpies of formation, ΔfHmo(liq/cr) of diphenyl ether substituted with methyl, methoxy, and hydroxyl substituents were measured by the high-precision combustion calorimetry. Enthalpies of vaporization/sublimation Δl,crgHmo(298.15 K) of these compounds were obtained by the transpiration method. Enthalpies of fusion of 2- and 4-hydroxy-diphenyl ether were measured by differential scanning calorimeter. Gas-phase enthalpies of formation ΔfHmo(g, 298.15 K) of substituted diphenyl ethers calculated by the G4 method were in an excellent agreement with the experimental results. Enthalpies of the hydrogenation/dehydrogenation reactions of diphenyl ether derivatives were estimated and compared with the data available for other potential LOHC. A set of thermodynamic properties of diphenyl ether derivatives of benchmark quality was recommended for thermochemical calculations. Equilibrium temperatures of hy...