고분자 전해질형 연료전지의 양극촉매로의 응용을 위한 나노구조가 제어된 팔라듐-백금 및 백금-니켈 합금 촉매의 제조 및 특성 분석

다국어 초록 (Multilingual Abstract)

Polymer electrolyte fuel cells (PEMFCs) are an electrochemical energy conversion device that convert the chemical energy into the electrical energy. Compared to other types of fuel cells, PEMFCs can produce electricity at low temperature as well as are high stability in on-off cycles, which makes them more suitable for the primary power source of zero-emission electric vehicles. Due to the high cost, however, the commercialization of PEMFCs would be impeded. The cost analysis for the PEMFCs system indicates that the electrocatalyst accounts for more than 30% in stack cost. Therefore, the development of low-cost electrocatalyst would be essential for the wide-spread use of PEMFC systems. Although non-precious metal-based materials have been suggested as the alternative catalyst for currently employed Pt-based electrocatalyst, their activity and stability are far from the level for the application to fuel cell stack. Instead, it is more practical to improve the activity of Pt-based electrocatalyst so as to decrease the amount of Pt usage for the reduction of the cost for electrocatalyst.
In this work, two approaches have been applied to enhance the catalytic performance of Pt-based electrocatalyst for oxygen reduction reaction (ORR).
First, carbon-supported PdPt core-shell nanoparticles with highly uniform size (PdPt/C-CS) were prepared by a simple method. The core-shell structure was confirmed using STEM and EDX analysis. The ORR activity of PdPt/C-CS was measured to be 1.5 times higher than a commercial carbon-supported Pt (Pt/C). In addition, the PdPt/C-CS showed higher unit-cell performance than Pt/C when it was used as the electrocatalyst for the cathode. The large enhancement in the ORR performance can be attributed to its core-shell structure. The catalytic activities of PdPt/C-CS were largely enhanced compared to those Pt/C commercial.
Second, Carbon-supported Pt-Ni alloy hollow nanoparticles with highly uniform size (PtxNiy/C-H) were prepared by a simple one-step method. Hollow structure of PtxNiy/C-H was confirmed by STEM and TEM-EDX line-scanning profile. The shell of PtxNiy/C-H was observed to have a Pt-enriched surface layer and an inner layer of PdNi alloy. Among the PtxNiy/C-H catalysts, PtNi2/C-H showed best ORR performance, which is approximately 2-and 5-fold enhanced mass-and specific activity compared to those of Pt/C.

목차 (Table of Contents)

• 1. 서 론 ·······················································································1
• 2. 이론적 배경 ···········································································4
• 2. 1. 산소환원반응 ····································································4
• 2. 2. 코어-쉘(core-shell)과 중공형(hollow) 합금 촉매 ····5
• 3. 실 험 ·······················································································6
• 3. 1. 시약 및 재료 ·····································································6
• 3. 1. 1. PdPt 코어-쉘(core-shell) 합금 촉매 연구 ············6
• 3. 1. 2. PtNi 중공형(hollow) 합금 촉매 연구 ·······················6
• 3. 2. 실험 방법 ···········································································7
• 3. 2. 1. PdPt 코어-쉘(core-shell) 합금 촉매 제조 ·············7
• 3. 2. 2. PtNi 중공형(hollow) 합금 촉매 제조 ·······················7
• 3. 2. 3. 단위전지(Unit cell) 제작 ············································8
• 3. 3. 특성 분석 ···········································································9
• 3. 3. 1. X선 회절 분석 ······························································9
• 3. 3. 2. 전자현미경 분석 ··························································9
• 3. 3. 3. 산소환원반응 평가 ······················································9
• 3. 3. 4. 단위전지(Unit cell) 성능 평가 ··································10
• 4. 결과 및 고찰 ··········································································13
• 4. 1. PdPt 코어-쉘(core-shell) 합금 촉매 ···························13
• 4. 2. PtNi 중공형(hollow) 합금 촉매 ·····································35
• 5. 결 론 ························································································57
• 참고문헌 ······················································································60