A density functional theory study into the mechanism and reactivity in heterogeneous system

In chapter 2, fundamental theories and techniques in this thesis are introduced in detail, as well as VASP software packages. <br><br>Chapter 3 comprehensively introduces the mechanism of Fisher-Tropsch process on stepped Ru(0001) surface. In this part, two most possible mechanisms are both discussed: CO insertion and carbide mechanism. Additionally, the coverage effect is introduced to acquire more realistic results, based on which we reveal the selectivity, activity and ratedetermined step of Fisher-Tropsch process from syngas to C2 compounds.<br><br>Chapter 4 presents the distinct catalytic performances on three different types of NiO surface.

The methane combustion process is investigated as a probe on these surfaces. In this part, activation of methane is studied under different coordination environment of Ni2+, such as sheet NiO, cubic NiO and octahedral NiO represented by NiO(110), NiO(100) and NiO(111), respectively. The mechanism schemes of the pathway are all simulated to search the most favorable methane oxidation route.<br><br>Chapter 5 presents the calculation on Pt(111)/H2O interface to research the preference for CO adsorption in liquid with an advanced Molecular Dynamic (MD) approach, namely umbrella sampling.

Both the hollow site and the top site are simulated for CO adsorption and desorption with free energy chemisorption energy obtained.<br><br>In chapter 6, the slow-growth (SG) approach and constrained molecular dynamics (CMD) are adopted and combined to address the oxygen evolution reaction (OER) on the interface between water and IrO2(110) surface under electrostatic potential environment. The surface is terminated by adsorbed oxygen atoms on the iridium atoms to account for the electrochemical potential in experiments.

The different reaction pathways are discussed to figure out the most possible mechanism. In order to make the reaction environment closer to the realistic condition, a constant potential model is achieved by correcting constant potential charge via workfunction calculations. <br><br>