촉매의 계면 및 전자구조 조절을 통한 전이금속 촉매의 성능 향상 연구 : Design, optimization, and characterization of transition-metal catalysts for enhancing efficiency in water splitting applications = Interfacial Engineering and Electronic Structures Modulation of Transition-Metal Catalysts for Water Splitting

다국어 초록 (Multilingual Abstract)

The rapid depletion of fossil fuels and the increasing global CO₂ emissions have underscored the urgent need for efficient energy conversion technologies. Hydrogen, as a high-energy-density and carbon-neutral fuel, is crucial for the future of sustainable energy, particularly in large-scale hydrogen production. This thesis investigates the development of advanced transition-metal electrocatalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), focusing on how elemental doping, heterostructures, and molecular coordination impact the electronic properties of these materials.

In Chapter 1, the international energy crisis is introduced, along with the theoretical framework of Density Functional Theory (DFT) used to model hydrogenation reactions at the atomic level. The hydrogen electrode model (CHE model) is also presented as a computational tool for predicting reaction mechanisms.

Chapter 2 explores NiCo₃P.C heterostructured interfaces, where NiCo₃P nanoneedles are combined with reduced graphene. DFT calculations reveal that high interface coupling improves conductivity and enhances the adsorption of reaction intermediates, resulting in thermoneutral hydrogen adsorption (ΔGH* = −0.10 eV) and low OER overpotentials, demonstrating bifunctional catalysis.

In Chapter 3, the Fe & Ce co-doped Co₃O₄/g-C₃N₄ heterostructures are analyzed, where the combination of Fe 3d & Ce 4f orbitals enhances charge mobility and optimizes the d-band center. This material shows optimal HER conditions (ΔGH* near thermoneutrality) and the lowest OER barriers (η ~ 0.32 V), outperforming all Co₃O₄ variants.

Chapter 4 investigates the multistep catalysis of NiCo₂S₄ in its unfunctionalized, bipyridine-functionalized, and doped form (V@NiCo₂S₄/bpy). The analysis of PDOS, d-band, CDD, and adsorption shows that bipyridine coordination improves charge transfer at the interface, while V-doping generates favorable states near the Fermi level. The catalytic roles of V, Ni, and Co sites are defined: V sites promote HER, Ni sites reduce OER energy barriers, and Co sites optimize ORR performance.

Chapter 5 integrates these findings to propose design principles for future multi-dopant systems, machine-learning-guided catalyst searches, and the validation of predicted active sites and mechanisms. This work provides a comprehensive, atomic-level understanding of how electronic structure manipulation, interface engineering, and molecule coordination can be leveraged to develop the next generation of efficient, selective, and stable electrocatalysts for water-splitting reactions in fuel cells.

목차 (Table of Contents)

• Chapter1 1
• Chapter 2 43
• Chapter 3 93
• Chapter 4 134
• Chapter5 183
• Conclusion 181