| 摘要: | 由於環境汙染與能源需求問題日益漸增，發展潔淨和可持續再生能源已是當務之急。氫(H2)具有高能量密度和零碳排放特性，被認為是傳統化石燃料的替代品。目前，析氫反應(hydrogen evolution reaction, HER)是最先進製氫技術之一，其中開發高效穩定且適用於廣泛 pH 值的電催化劑至關重要。
本研究分為兩個部分。第一部分透過油胺法合成氫化鈀(palladium hydride, PdH)並添加 3d 過渡金屬(例如:鐵、鈷及鎳)以形成二元合金觸媒(PdFeH、PdCoH 及PdNiH)研究其兩者合金化之效果。其中以PdCoH 的修飾效果最佳，在HER 反應中具有最低的過電位(22 mV)及出色的Tafel 斜率(24 mV dec-1)，且質量活性(mass activity, MA)(494 mA/gPd)為PdH0.3 的2.2 倍，展現出優異的HER 活性。
第二部分是以不同比例的鈷添加到鈀氫化物的結構中，透過X 光電子能譜儀 (X-ray photoelectron spectroscopy, XPS)及CO 剝離測試(CO-stripping)的結果顯示，摻入適量的鈷與氫原子，不僅能減少了表面鈀的氧化進而改變了鈀的電子結構，從中平衡了Pd 的氫氣吸附能(hydrogen adsorption energy, Hads)。在酸性和鹼性電解液中，Pd3CoH 展現優異的HER 性能，具有極低的過電位(18 和32 mV)和Tafel 斜率(22 和74 mV dec-1)且表現出優異的穩定性。值得注意的是，Pd3CoH 在鹼性中經過5000 圈穩定度測試後，由於親氧的鈷作為保護層和提供豐富的活性位點，整體的電催化活性顯著提升且加快了HER 的反應動力學。本研究結合了氫化物與過渡金屬修飾的優點設計了鈀基合金氫化物，因為協同效應使其在酸性及鹼性HER 中皆展現出卓越的活性及穩定度。此研究從材料設計到其應用皆提供HER 及其他電催化領域新穎的思維及方向。;Due to the increasing environmental pollution and energy demand, the development of clean and sustainable renewable energy has become a top priority.
Hydrogen (H2), which owns high energy density and zero carbon emissions, is considered to be an alternative to traditional fossil fuels. Currently, hydrogen evolution reaction (HER) is one of the most advanced H2 production technologies, and the development of efficient and stable electrocatalysts applied in a wide range of pH values is crucial for HER economy.
This study is divided into two parts. In the first part, palladium hydride (PdH) and Pd alloy hydrides such as PdFeH, PdCoH, and PdNiH are prepared by oleylamine (OAm) method. Among all samples, for the HER performance, PdCoH shows the best modification effect during HER, including the lowest
overpotential (η10) at 10 mA cm-2 (22 mV), excellent Tafel slope (24 mV dec-1), and the highest mass activity (MA), which is 2.2 times higher than that of PdH0.3.
In the second part, PdxCoH (Pd9CoH, Pd3CoH and PdCoH) are synthesized by OAm method. The X-ray photoelectron spectroscopy (XPS) and CO-stripping reveal that with proper Co and H addition, surface Pd oxidation can be retarded.
In addition, the addition of Co modifies the electronic structure of Pd, thereby reducing the hydrogen adsorption energy (Hads) of Pd, and improving HER activity. Among all samples, Pd3CoH exhibits the best HER activity with the lowest η10 (18 and 32 mV), smallest Tafel slope (22 and 74 mV dec-1) and excellent stability of 5000 cycles in acidic and alkaline solutions, respectively. Notably, after the stability test in alkaline solution, the electrocatalytic activity and the kinetics of HER are significantly improved due to the oxyphilic cobalt working as protection layer and providing abundant active sites. In this study, Pd-based alloy hydride is designed to combine the advantages of hydride and transition metal modification, which exhibits excellent HER activity and stability in both acidic and alkaline. We provide novel thinking and strategy for the future development and perspective of catalysts from material design to application. |
