| Hydrogen is wildly considered as a clean alternative energy.Hydrogen as a nontoxic,odourless,products of combustion is water,and the calorific value is three times as much as gasoline,so it's become the most ideal clean energy.However,how to efficient and lower energy to produce H2 is still an unsolved problem.Therefore the metal catalyst research received extensive attention of research workers.Based on first principles and generalized gradient approximation,we studied the reaction process of H2 O molecule adsorption and dissociation on cluster,and analysis the dynamics process through the reaction path.First.We perform calculations to explore the mechanism for complete generation of the H from a single H2 O molecule on Pt4 cluster.We have found that H2 O molecule incline to adsorb on the top sites of the Pt4 cluster though test the adsorption of H2 O molecule on top,bridge and face sites by using structures optimization and frequency analysis.We finally obtained 4 stable structures of H2O@Pt4 except the same one,and corresponding product,and transition state?TS?,the reaction path is analyzed.To confirmed the relations of reactant,transition state and product by the IRC calculation.The result implied that it is go through two step of H2 O dissociated into H2 on Pt4 cluster,moreover,the energy barrier of two step are just coincide solar light.Secondly,we use the CO oxidation to extract the O atom of the byproduct of first reaction O@Pt4,CO+O?CO2,the energy barrier of this reaction is only 0.36 eV,last we got the pure Pt4 cluster,and realize the cluster reuse.Second.We studied the hydrolysis mechanism of Pt7 cluster.First,we researched the H2 O molecule adsorption ability on Pt7 cluster by DFT calculation,the calculation shows that whether we put the H2 O adsorbed on top,bridge and face sites on Pt7 cluster,the result show that H2 O molecule incline to adsorb on top sites of Pt7 cluster,we obtained 12 stable structures H2O@Pt7 by energy stability and frequency analysis.Then,we construct two product of H@OH@Pt7 and H2@O@Pt7 correspond to the 12 reactants,and calculated the TS and IRC.The present result that same reactants extraction H atom from H2 O molecule though one step,while other reactants extraction H2 atom though one step.Difference is that the energy barrier and reactionenthalpy,namely,hydrogen production efficiency is different.The findings provide us a new idea that one can choose an appropriate reaction path to generate H according to the energy consumption and efficiency of hydrogen production.Third.Based on the previous research we also explore the mechanism of hydrogen production on Pt6 Cu cluster.Through tedious structures optimization and frequency analysis,the result show that H2 O molecule tend to adsorbed on the top site of Pt6 Cu cluster.Finally,we got 18 stable structures of H2O@Pt6Cu by test adsorption sites.We construct two product of H@OH@Pt6Cu and H2@O@Pt6Cu correspond to the 12 reactants,and calculated the TS and IRC.The present result that doping one copper atom of Pt7 cluster extraction H atom from H2 O molecule though one step,calculating the IRC and finding the energy barriers are lower than production H on Pt7 cluster,which is a promising way to produce hydrogen. |
PDF Full Text Request