The Effect Of Support In NH₃BH₃ Dehydrogenation: A Firstprinciples Study

With the high-speed development of society, the science and technology continue to make progress, the demand of fossil energy consumption also continue to increase. As we know, the fossil energy is the main source of energy in the past, however, the excessive consumption of fossil energy result in the fossil energy is running out, the amount of fossil energy cannot satisfy the need. So, in search of new clean energy becomes the urgent matter.Hydrogen has attracted great interest because it is a good energy carrier. And it is a very promising research to apply the good energy carrier--hydrogen in the automotive industry. At present, one of the most challenging issues is hydrogen storage in combination with fuel cells for automotive applications. Too many hydrogen storage materials have been studied and among them ammonia borane（NH₃BH₃） is one of the very promising hydrogen storage material. Although a lot of research has been performed to study ammonia borane（NH₃BH₃）, here we investigate the effect of supports in NH₃BH₃ dehydrogenation by comparing the dehydrogenation of NH₃BH₃ with supports to the dehydrogenation of NH₃BH₃ without supports.In this manuscript, the first-principles method was used to study the effect of supports in NH₃BH₃ dehydrogenation and different supports were used to analyze.Chapter 1, human beings are facing energy crisis and serious environmental pollution, in search of new clean energy becomes the urgent matter. As a new energy carrier, hydrogen, has attracted great interest. The most challenging issue is hydrogen storage in combination with fuel cells for automotive applications. Several hydrogen storage materials were introduced. Among them ammonia borane（NH₃BH₃） is one of the very promising hydrogen storage material and it has attracted more and more attention. A lot of research were performed to investigate the dehydrogenation of ammonia borane（NH₃BH₃） and in this article we will use the first-principles method to study the effect of supports in NH₃BH₃ dehydrogenation.Chapter 2, the first-principles method, the density functional theory, the Vienna Ab-initio Simulation Package and so on, were introduced briefly.Chapter 3, in order to determine the effect of supports in ammonia borane dehydrogenation, first-principles calculations were carried out to study the dehydrogenation of isolated ammonia borane（NH₃BH₃, AB） and AB adsorbed on different graphene supports. The dehydrogenation barrier of the AB monomer was 1.67 e V. The barrier changed to 0.68 e V on perfect graphene（G）, 0.75 e V on single-vacancy graphene（S-G）, 1.28 e V on B-doped graphene（B-G）, 1.48 e V on N-doped graphene（N-G）, 1.66 e V on 585 double-vacancy graphene（585-G）, and 0.57 e V on 55–77 reconstructed single-vacancy graphene（5577-G） supports, respectively. When the support was G, S-G, or 5577-G, the dehydrogenation barrier was lower than the B–N bond cleavage energy. Thus, H2 was more easily released than NH3. By analyzing the atomic charges, it was obtained that charge transfer from the supports to the molecule can decrease the barrier, but the amount of the charge transfer seems to have no effect on the barrier. Furthermore, the dehydrogenation barrier also has the trend to increase with decreasing adsorption energy.Chapter 4, in order to determine the effect of supports in ammonia borane dehydrogenation, first-principles calculations were carried out to study the dehydrogenation of ammonia borane（NH₃BH₃, AB） adsorbed on other different graphene supports: Mg3N2（111）,Fe（111） and hydrogen passivated graphene. In this part, the van der Waals interaction was also considered.Chapter 5, as a new energy carrier, hydrogen has many advantages. The research of hydrogen storage material is very meaningful and promising, hydrogen-powered vehicle will come true through our unremitting efforts.