비정질 니켈-구리 이중 금속 촉매의 구조적 특성에 따른 전기화학적 암모니아 산화반응의 활성 향상 연구 = Study on the enhancement of electrocatalytic activity toward electrochemical ammonia oxidation by the structural characteristics of amorphous Ni-Cu bimetallic electrocatalysts

다국어 초록 (Multilingual Abstract)

The ammonia oxidation reaction (AOR) has gained attention as a potential alternative to the oxygen evolution reaction (OER) because it can be operated at a lower theoretical potential (0.056 V vs. RHE) than the sluggish OER (1.227 V vs. RHE). However, the effective utilization of AOR requires the development of suitable catalysts. Platinum-based catalysts exhibit high activity for AOR, but their high cost and poisoning by nitrogen-containing adsorbed species during the reaction limit their practical application. To overcome these limitations, research on low-cost non-precious metal catalysts has been widely studied. Nickel-based catalysts not only have exhibited AOR activity but also have shown improved performance when copper is added.
In this study, an amorphous Ni-Cu bimetallic electrocatalyst was synthesized by performing 50 cycles of cyclic voltammetry over potential range of 0.05 to 1.60 V vs. RHE in 1 M KOH+1 M NH4OH as electrolyte. SEM, TEM, and XRD analysis confirmed the amorphous structure of the catalyst synthesized through in situ electrochemical oxidation method. XRS and Raman spectroscopy exhibited the presence of metal oxyhydroxide phase. Furthermore, valence band spectra indicated that the metal oxyhydroxide phase and copper incorporation significantly influenced the electronic structure of the catalyst.
The i-NiCu exhibited the potential of 1.48 V vs. RHE at 100 mA cm-2, which is 159 mV lower than the OER potential. The Tafel slope was 33.75 mV dec-1 indicating faster reaction kinetics compared to other electrocatalysts. Electrochemical impedance spectroscopy revealed that both Cu incorporation and the amorphous structure contributed to reduced charge-transfer resistance and enhanced reaction kinetics. In addition, i-NiCu retained 94% of its initial potential after stability test for 100 h. These results demonstrate that the in situ synthesis approach not only simplifies the catalyst preparation process but also offers an effective strategy for designing high-performance AOR catalysts.

목차 (Table of Contents)

• - 목 차 - i
• List of Figures iii
• Abstract vi
• 1. 서론 1
• 2. 이론적 배경 4
• 2.1. 수전해 4
• 2.2. 암모니아 산화 반응 5
• 2.3. 비정질 구조 촉매 7
• 3. 실험 9
• 3.1. 시약 및 재료 9
• 3.2. 실험 방법 10
• 3.2.1. 전극 기판의 전처리 10
• 3.2.2. 전구체 용액 제조 및 도포 10
• 3.2.3. 촉매 전극의 제조. 11
• 3.3. 특성 분석 12
• 3.3.1. 구조적 특성 분석 12
• 3.3.2. 화학적 특성 분석 12
• 3.3.3. 전기화학적 성능 평가 13
• 4. 결과 및 고찰 15
• 4.1. 소재 특성 분석 15
• 4.1.1. 구조적 분석 15
• 4.1.2. 화학적 분석 25
• 4.2. 전기화학적 성능 평가 37
• 4.2.1. 암모니아 산화 반응 활성 분석 37
• 4.2.2. 임피던스 분석 47
• 4.2.3. 장시간 안정성 평가 50
• 5. 결론 52
• 참고문헌 54