본 석사학위 과정을 통하여 Graphene의 defect 형성 메커니즘 규명, 나노 촉매 합성방안 제시 및 형성 메커니즘 규명 그리고 고체산화물 연료전지의 전극 및 전해질 설계까지 DFT를 이용한 다양한 촉매설계를 수행하였다. 본 논문에서 사용된 밀도범함수이론 (Density Functional Theory, DFT)은 오늘날 촉매설계, 신소재 설계, ...
본 석사학위 과정을 통하여 Graphene의 defect 형성 메커니즘 규명, 나노 촉매 합성방안 제시 및 형성 메커니즘 규명 그리고 고체산화물 연료전지의 전극 및 전해질 설계까지 DFT를 이용한 다양한 촉매설계를 수행하였다. 본 논문에서 사용된 밀도범함수이론 (Density Functional Theory, DFT)은 오늘날 촉매설계, 신소재 설계, 반응메커니즘 분석 등에 널리 이용되고 있다. 이러한 접근방법은 모델, 파라미터의 피팅 또는 실험값 등의 사전지식 없이 Schrödinger 방정식 등과 같이 정립된 물리학 법칙으로부터 직접적으로 접근할 수 있고, 최근 컴퓨터 계산성능의 향상으로 인해 특정 목적의 물성을 갖는 신소재의 신속∙정확한 설계가 가능하다는 장점이 있다. Chapter 1에서는 그래핀 구조에 결함을 발생시켰을 때 카본간의 구조적 화학적 변화로부터 구조적, 화학적 특성이 변화될 수 있으며, 이를 광자 및 산소 플라즈마를 조사함에 따라 조절 할 수 있음을 보였다. Chapter 2에서는 나노 입자의 성장 메커니즘과 환원제의 농도 및 종류에 따른 모양을 예측하였다. 또한, 이러한 흡착선호도를 각 작용기의 기여도를 통하여 분석함으로써 맞춤형의 나노 입자 형성을 위한 방안을 제시하였으며, Chapter 3에서는 연료전지의 개발을 위한 방안으로 구조적 결함을 형성시켰을 때 YSZ 전해질에서 산소환원반응의 향상되는 현상과 PBCMO전극에서의 엑솔루션 현상을 규명하여 이를 응용한 전극 및 전해질 제조방안을 제시하였다.
주요어: DFT, 그래핀, defect, 나노입자, YSZ, 엑솔루션
본 석사학위 과정을 통하여 Graphene의 defect 형성 메커니즘 규명, 나노 촉매 합성방안 제시 및 형성 메커니즘 규명 그리고 고체산화물 연료전지의 전극 및 전해질 설계까지 DFT를 이용한 다양한 촉매설계를 수행하였다. 본 논문에서 사용된 밀도범함수이론 (Density Functional Theory, DFT)은 오늘날 촉매설계, 신소재 설계, 반응메커니즘 분석 등에 널리 이용되고 있다. 이러한 접근방법은 모델, 파라미터의 피팅 또는 실험값 등의 사전지식 없이 Schrödinger 방정식 등과 같이 정립된 물리학 법칙으로부터 직접적으로 접근할 수 있고, 최근 컴퓨터 계산성능의 향상으로 인해 특정 목적의 물성을 갖는 신소재의 신속∙정확한 설계가 가능하다는 장점이 있다. Chapter 1에서는 그래핀 구조에 결함을 발생시켰을 때 카본간의 구조적 화학적 변화로부터 구조적, 화학적 특성이 변화될 수 있으며, 이를 광자 및 산소 플라즈마를 조사함에 따라 조절 할 수 있음을 보였다. Chapter 2에서는 나노 입자의 성장 메커니즘과 환원제의 농도 및 종류에 따른 모양을 예측하였다. 또한, 이러한 흡착선호도를 각 작용기의 기여도를 통하여 분석함으로써 맞춤형의 나노 입자 형성을 위한 방안을 제시하였으며, Chapter 3에서는 연료전지의 개발을 위한 방안으로 구조적 결함을 형성시켰을 때 YSZ 전해질에서 산소환원반응의 향상되는 현상과 PBCMO전극에서의 엑솔루션 현상을 규명하여 이를 응용한 전극 및 전해질 제조방안을 제시하였다.
Over the past few decades, density functional theory (DFT) calculations have been widely used to find and develop materials for various purposes such as low price, high activity, and durability under diverse reaction conditions. Understanding the nature at the atomic level enables fundamental inform...
Over the past few decades, density functional theory (DFT) calculations have been widely used to find and develop materials for various purposes such as low price, high activity, and durability under diverse reaction conditions. Understanding the nature at the atomic level enables fundamental information to be obtained from bottom-up approaches for designing new types of material. Until now, many experimental approaches have been used as “trial and error” methods to identify and develop new materials. Owing to high experimental costs and instrument limitations, experimental approaches have experienced difficulties in massive material screening. Recently, the time and cost for massive material screening with high accuracy have been sharply decreased due to the advances in computer performance. Therefore, strong demand has arisen to “shorten the time for the discovery and development of specialized materials in various research and industry fields” by using computational approaches. Consequently, we conducted DFT calculations with the following main aims. I. Demonstrating the defect formation mechanism, which can be precisely introduced into graphene using not only energy and dose from proton-irradiation but also an oxygen exposure by conventional reactive ion etching (RIE) system. Computational approaches used in combination with experiments have played an important role in elucidating the defect formation mechanism and evaluating the stability of graphene. II. Understanding the mechanism and the key factors influencing the particle growth, surface and bulk reactions. Through detailed analysis based on the thermodynamics and surface kinetics, we suggest the reaction mechanisms for diverse catalysis. III. Optimizing the composition and structure for enhanced catalysis. Through a quantitative comparison of materials, we provide many fundamental properties as well as the direction for experimental works. Based on quantitative analysis, we select candidate materials that meet our criteria and optimize the composition and structure. Our results identify the active sites of the reaction that may be involved in catalysis and also offer direction for designing more effective materials in various fields. Chapter 1 examines the possible mechanism and proportion of various defect forms on defective graphene structures by proton irradiation and oxygen plasma. Chapter 2 investigates how the adsorption strengths and configurations of the adsorbates are changed by the surface coverage and binding functional groups. These changes in the adsorption features affect the surface energies, and hence the sizes and morphologies of the nanoparticles (NPs). Chapter 3 reveals the underlying mechanism of enhanced oxygen incorporation near the YSZ GB by investigating the key elementary steps of oxygen incorporation; yttrium segregation, oxygen vacancy formation, and oxygen adsorption. The characteristics of the exsolution phenomenon are identified on various perovskite materials, suggesting the tailored particle size and phase on the reduction reaction conditions.
Over the past few decades, density functional theory (DFT) calculations have been widely used to find and develop materials for various purposes such as low price, high activity, and durability under diverse reaction conditions. Understanding the nature at the atomic level enables fundamental information to be obtained from bottom-up approaches for designing new types of material. Until now, many experimental approaches have been used as “trial and error” methods to identify and develop new materials. Owing to high experimental costs and instrument limitations, experimental approaches have experienced difficulties in massive material screening. Recently, the time and cost for massive material screening with high accuracy have been sharply decreased due to the advances in computer performance. Therefore, strong demand has arisen to “shorten the time for the discovery and development of specialized materials in various research and industry fields” by using computational approaches. Consequently, we conducted DFT calculations with the following main aims. I. Demonstrating the defect formation mechanism, which can be precisely introduced into graphene using not only energy and dose from proton-irradiation but also an oxygen exposure by conventional reactive ion etching (RIE) system. Computational approaches used in combination with experiments have played an important role in elucidating the defect formation mechanism and evaluating the stability of graphene. II. Understanding the mechanism and the key factors influencing the particle growth, surface and bulk reactions. Through detailed analysis based on the thermodynamics and surface kinetics, we suggest the reaction mechanisms for diverse catalysis. III. Optimizing the composition and structure for enhanced catalysis. Through a quantitative comparison of materials, we provide many fundamental properties as well as the direction for experimental works. Based on quantitative analysis, we select candidate materials that meet our criteria and optimize the composition and structure. Our results identify the active sites of the reaction that may be involved in catalysis and also offer direction for designing more effective materials in various fields. Chapter 1 examines the possible mechanism and proportion of various defect forms on defective graphene structures by proton irradiation and oxygen plasma. Chapter 2 investigates how the adsorption strengths and configurations of the adsorbates are changed by the surface coverage and binding functional groups. These changes in the adsorption features affect the surface energies, and hence the sizes and morphologies of the nanoparticles (NPs). Chapter 3 reveals the underlying mechanism of enhanced oxygen incorporation near the YSZ GB by investigating the key elementary steps of oxygen incorporation; yttrium segregation, oxygen vacancy formation, and oxygen adsorption. The characteristics of the exsolution phenomenon are identified on various perovskite materials, suggesting the tailored particle size and phase on the reduction reaction conditions.
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