Theoretical Investigations On Novel Hydrogen Storage Materials

The increasingly serious energy crisis and environmental pollution caused by the excessive use of fossil fuels have been prompting us to aggressively seek a clean and sustainable energy source.The hydrogen economy has enormous social and technical appeal as an attractive solution to the fundamental energy concerns.However,the absence of useful storage technologies is a serious problem greatly limiting the adavance of hydrogen.Currently,hydrides of light-weight elements are the most ideal hydrogen carrier due to their high gravimetric and volumetric hydrogen content.Nevertheless,the release hydrogen temperature and poor selectivity of such materials are still unresolved.Therefore,in addition to effective experimental investigations,more theoretical researches are needed to modify them.(1)Liquid organic hydrogen carrier(LOHC)has great potential in realizing large-scale hydrogen transportation,but the unfavorable enthalpies of dehydrogenation(ΔHd=60-75 kJ/mol-H2)is the major obstacle in the development of such hydrogen storage materials.We conduct a systematic theoretical research on ΔHd of N-heterocyclic compounds substituted with alkali/alkaline earth metals.We found that the ΔHd of these metallo-N-heterocycles are dependent on the electronegativity(Z)of the metals.Through charge analysis,we further elaborated on the cause of the dehydrogenation enthalpy change internal micro factors.(2)Ammonia is an ideal hydrogen carrier with extremely high hydrogen capacity.Recent experiments have shown that Ru clusters supported on Sm2O3 have excellent catalytic activity under mild reaction conditions.Therefore,we systematically investigated-the reaction mechanism of ammonia synthesis over Ru/Sm2O3.Results show that the Ru/Sm2O3 catalyst can generate the surface hydride(Sm-H)in situ through the surface of Sm2O3.And the Sm-H species can not only promote the activation of nitrogen but also directly participate in the ammonia synthesis process.(3)Recent experiments have indicated that a novel Pd-based catalyst CaPdH2 has excellent catalytic performance.Thus,we conducted a theoretical research on the selective hydrogenation of acetylene over CaPdH2 catalyst.Our results indicate that the presence of Ca ions in CaPdH2 have changed the adsorption of acetylene and ethylene,effectively improving the selectivity of ethylene.The surface H species of CaPdH2 can not only participate in the reaction,but also regulate the adsorption strength of molecules through the hydrogen content.