고온 폴리올 방법을 통한 산소환원반응용 고분산 PtNi 합금 촉매 제조 및 특성 분석 = Synthesis and Characterization of Highly Dispersed PtNi Alloy Catalysts for the Oxygen Reduction Reaction via a High-Temperature Polyol Method

다국어 초록 (Multilingual Abstract)

Polymer electrolyte membrane fuel cells (PEMFCs) have gained significant attention as a promising next-generation energy conversion technology, owing to their high power density and eco-friendly operation. However, the oxygen reduction reaction (ORR) at the cathode is inherently sluggish, acting as the rate-determining step for the entire process. To address this, Pt-based catalysts are widely utilized, yet, their prohibitive cost and limited long-term durability continue to pose major challenges to large-scale commercialization.
A promising strategy to address these challenges is alloying Pt with transition metals such as Ni, Co, and Fe. This approach modulates the electronic structure and surface coordination environment of Pt, thereby enhancing ORR activity. Among various Pt-based alloys, Pt–Ni alloys are particularly noteworthy for their superior ORR activity and commercial potential. However, conventional synthesis requires high-temperature annealing (above 600 °C) to induce alloying, which frequently leads to particle agglomeration and a reduced electrochemically active surface area (ECSA). Although poorly dispersed Pt–Ni catalysts may exhibit high exchange current densities in half-cell tests, they often fail to meet performance expectations in membrane electrode assemblies (MEAs), particularly in the high-current-density region.
In this study, a modified polyol method was designed to synthesize highly dispersed Pt–Ni alloys in a single step via autoclave-based reduction at elevated temperatures. This approach significantly enhances the reduction kinetics of the metal precursors, thereby eliminating the requirement for post-synthesis high-temperature annealing. It was systematically investigated the effects of reaction time and temperature to elucidate how synthesis conditions influence the dispersion, structure, and composition of the resulting catalysts, and consequently, their electrochemical performance. Through optimization, the catalyst synthesized at 250 °C for 3 h exhibited the most superior catalytic activity.
Electrochemical evaluations conducted in 0.1 M HClO4 revealed that the optimized catalyst exhibited an initial mass activity of 0.82 A/mgPt, significantly outperforming commercial Pt/C. Furthermore, after 30,000 accelerated durability test (ADT) cycles, the electrochemically active surface area (ECSA) and mass activity decreased by only 7.8% and 27.7%, respectively, demonstrating exceptional long-term stability. Membrane electrode assembly (MEA) tests further validated these results. While a cell using commercial Pt/C at the cathode (0.05 mgPt/cm2) yielded a peak power density of only 0.25 W/cm2, the cell employing the synthesized Pt–Ni alloy catalyst achieved a significantly higher peak power density of 0.80 W/cm2 under identical conditions. The maintained higher cell voltage across the low-current-density region further confirms that the Pt–Ni catalyst delivers superior electrochemical performance even under practical single-cell operating conditions.

목차 (Table of Contents)

• List of tables ⅱ
• List of figures ⅳ
• ABSTRACT ⅶ
• ChapterⅠ. 고온 폴리올 방법을 통한 산소환원반응용
• 고분산 PtNi 합금 촉매 제조 및 특성 분석
• 1. Introduction 1
• 1.1 이론적 배경 1
• 1.2 산소환원반응용 PtNi 합금 촉매 3
• 2. 실험방법
• 2.1. 재료 및 시약 5
• 2.2. 촉매 합성 5
• 2.3. 물리적 특성 분석 방법
• 2.3.1 X선 회절 분석 6
• 2.3.2 전자 현미경 분석 6
• 2.3.3 유도결합 플라즈마 방출 분광 분석 7
• 2.3.4 X선 광전자 분광법 7
• 2.4. 전기화학적 특성 분석 방법
• 2.4.1 반쪽 전지 전기화학적 특성 분석 7
• 2.4.2 단위 전지 전기화학적 특성 분석 8
• 3. 결과 및 고찰
• 3.1. 구조 및 특성 분석 9
• 3.2. 전기화학적 특성 분석 33
• 4. 결론 50
• 참고문헌 52