具有高活性和高穩定性鈀鐵合金氫化物應用於酸性介質析氫反應之研究;Highly Active and Stable Pd-Fe Hydride Electrocatalyst for Hydrogen Evolution Reaction in Acidic Media

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Title:	具有高活性和高穩定性鈀鐵合金氫化物應用於酸性介質析氫反應之研究;Highly Active and Stable Pd-Fe Hydride Electrocatalyst for Hydrogen Evolution Reaction in Acidic Media
Authors:	李志賢;Lee, Zhi-Xian
Contributors:	材料科學與工程研究所
Keywords:	電催化;析氫反應觸媒;氫化鈀;鈀鐵合金;鈀鐵合金氫化物;觸媒再生;electrocatalysis;hydrogen evolution reaction catalyst;palladium hydride;Pd-Fe alloy;Pd-Fe Alloy hydride;catalyst refreshment
Date:	2024-07-10
Issue Date:	2024-10-09 15:40:15 (UTC+8)
Publisher:	國立中央大學
Abstract:	隨著科技的快速發展，石化燃料等能源消耗及其造成的環境汙染問題逐漸受到重視。由於氫氣的高能量密度和零碳燃燒等特性，有取代傳統化石燃料的潛力，因此電催化水分解產氫被視為是一種有前途的解決方案，然而緩慢的動力學限制了析氫反應的進行，為了加速整體產氫速率，設計出高活性的電催化觸媒在析氫反應中扮演著決定性角色。本研究分成兩個部分做討論，第一部分會介紹以鈀作為高成本鉑基觸媒的替代材料，並利用導入過渡金屬Fe進行合金化和將氫作為間隙原子插入鈀晶格兩種策略修飾鈀的催化活性，解決鈀觸媒因和氫的強親和力所造成的低活性。本研究利用感應耦合電漿技術、X光繞射技術、X光光子能譜技術和X光吸收光譜技術來對觸媒進行分析，獲得觸媒的元素組成、晶體結構、價態組成等材料性質。並進行電化學分析已獲的觸媒的HER性能。本研究成功以油胺法合成出碳負載的鈀鐵合金氫化物奈米顆粒，為了瞭解鈀/鐵比例和析氫反應活性的關係，本研究設計了三中不同比例(1:1、3:1、9:1)的鈀鐵合金氫化物觸媒，相較於做為對照組的純鈀觸媒，鈀鐵合金氫化物在酸性介質中表現出了優異的活性以及穩定性，其中Pd3FeH表現了最出色的HER性能，在10 mAcm-2時的過電位為41 mV，Tafel斜率為17 mVdec-1，經過5000圈的加速降解測試，在10 mAcm-2時的過電位保持41 mV，Tafel斜率為14 mVdec-1，進行比較後可以發現，適當的鈀/鐵比例可以使觸媒的活性及穩定性有最大幅度的提升。第二部分會將失去活性的鈀鐵合金氫化物觸媒經過適當熱處理後使其再生，並比較不同的熱處理對鈀鐵合金氫化物觸媒的影響，探討如何設計處最佳的熱處理條件。經過H2氣氛下200℃維持300分鐘的熱處理後，ADT的過電位衰退率從160%降至35%，Tafel斜率從276%降至28%。本研究成功結合了氫化物與過度金屬合金化之優點，設計了用於酸性介質HER的Pd3FeH觸媒，其具有高活性及優異的電化學穩定性，且使已失活之觸媒成功再生，恢復活性，可繼續使用。 ;With the rapid advancement of technology, the consumption of energy sources such as fossil fuels and the resulting environmental pollution have garnered increasing attention. Due to its high energy density and zero-carbon combustion characteristics, hydrogen is considered a promising alternative to traditional fossil fuels. Consequently, hydrogen production via electrocatalytic water splitting is seen as a promising solution. However, the slow kinetics of the hydrogen evolution reaction (HER) poses a significant limitation. To accelerate the overall hydrogen production rate, the design of highly active electrocatalysts plays a decisive role in the HER process. This study is divided into two parts. The first part introduces palladium (Pd) as an alternative material to high-cost platinum-based catalysts. Two strategies are employed to modify the catalytic activity of Pd： alloying with the iron, and incorporating hydrogen as interstitial atoms into the Pd lattice. These strategies aim to address the low activity of Pd catalysts caused by their strong affinity for hydrogen. Inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) were used to analyze the catalysts, obtaining material properties such as elemental composition, crystal structure, and valence state composition. Electrochemical analysis was conducted to evaluate the HER performance of the catalysts. In this study, carbon-supported Pd-Fe alloy hydride nanoparticles were successfully synthesized using the oleylamine method. To understand the relationship between the Pd/Fe ratio and HER activity, three Pd-Fe alloy hydride catalysts with different ratios (1:1, 3:1, 9:1) were designed. Compared to the pure Pd catalyst used as a control, the Pd-Fe alloy hydride exhibited superior activity and stability in acidic media. Among them, Pd3FeH demonstrated the best HER performance, with an overpotential of 41 mV at 10 mA cm-2 and a Tafel slope of 17 mV dec-1. After 5000 cycles of accelerated degradation tests, the overpotential at 10 mA cm-2 remained at 41 mV, and the Tafel slope was 14 mV dec-1. The comparison revealed that an optimal Pd/Fe ratio could maximize the enhancement of both the activity and stability of the catalysts. The second part of the study focuses on the regeneration of deactivated Pd-Fe alloy hydride catalysts through appropriate heat treatment. It compares the effects of different heat treatments on the Pd-Fe alloy hydride catalysts and explores the optimal heat treatment conditions for catalyst regeneration. After heat treatment at 200°C in a H2 atmosphere for 300 minutes, the overpotential degradation rate of the accelerated degradation tests (ADT) decreased from 160% to 35%, and the Tafel slope degradation rate decreased from 276% to 28%. This study successfully combines the advantages of hydrides and transition metal alloying, designing a Pd3FeH catalyst for the HER in acidic media. The catalyst exhibits high activity and excellent electrochemical stability, and the deactivated catalyst can be regenerated, restoring its activity for continued use.
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