Abstract ---i List of contents ---ii List of tables ---iii List of figures ---iii I. Introduction ---1 II. Theory ---4 1. Density Functional Theory ---4 2. Plane wave basis set and pseudopotential ---5 3. Born-Oppenheimer approximation ---6 4. Radial Distribution Function ---7 Topic 1. Hydrogen Dissociation Reaction in acidic aqueous solution ---9 1. Atomic-scale reaction in the aqueous solution ---9 2. Methods ---10 3. Results and discussion ---12 Topic 2. Following a part of the conversion reaction of 2D material ---17 1. MoS2-to-Mo2C conversion mechanism ---17 2. Methods ---18 3. Results and discussion ---19 Topic 3. Proof of sputtering mechanism of untreated wet cells covered by a layer of graphene ---23 1. Role of graphene proven in computational chemistry ---23 2. Methods ---26 3. Results and discussion ---26 III. Summary ---30 Appendix: Input files of VASP ---31 References ---37 요약문 ---42