First-principles theoretical study of CO2 hydrogenation on Cu surfaces
First-principles molecular dynamics method is a quite powerful tool to elucidate and design chemical reactions at surfaces, interfaces and in solutions at the atomic level. In this talk, I will introduce recent studies in our group. The first one is on the activation and hydrogenation of CO2 over Cu catalyst [1--4]. Adsorption and reaction of CO2 on solid surfaces are attracting enormous interest because of their importance in industrial, energy and environmental management. To clarify reaction mechanisms and to identify important factors governing the reactivity of CO2 on solid surfaces are very important to develop more efficient catalysts or catalytic processes for utilization of CO2. To this end, we investigated CO2 adsorption, dissociation, and hydrogenation processes on Cu surfaces using van der Waals density functionals as implemented in our home made STATE (Simulation Tool for Atom TEchnology) program code . We theoretically proposed and experimentally verified vibrationally enhanced hydrogenation process of CO2 on Cu. As the second topic, I will discuss on the promotion mechanism of GaN single crystal growth in the Na flux method. The Na flux method is one of very promising techniques to grow large GaN single crystals with high quality. We have carried out first-principles molecular dynamics simulations. We also clarified the mechanism of suppression of poly-crystal growth and promotion of single crystal growth by C additives. Finally, we will discuss the enhancement of NO dissociation by hydrogen bonding on Cu surfaces, which is attracting enormous attention because of its importance in automobile emission control. We will discuss the origin for the weakening of N–O bond by hydrogen bonding.