磷化過程對氫氣生成反應在金屬磷化物上的影響

The effect of phosphating process for hydrogen evolution reaction on metal phosphides

許文騰(Hsu Weng-Teng)

指導教授 ： 王禎翰

國立臺灣師範大學/理學院/化學系/碩士(2021年)

https://doi.org/10.6345/NTNU202100970

摘要

由於析氫反應為一種有效產生再生氫氣燃料之方法且被研究出能在基礎上解決由化石燃料引發的能源危機，此論文主要探討如何最佳化磷化物以獲得最高效之析氫反應活性。合成金屬磷化物首先經過金屬氯化物和草酸之共沉澱並鍛燒 300oC 1 小時;金屬磷化物則透過金屬氧化物與次亞磷酸鈉而進行的氣固反應控制。再透過高解析感應耦合電漿質譜分析儀、掃描式電子顯微鏡、能量散射光譜儀、X 光粉末繞射分析儀、X 光光電子能譜儀鑑定金屬磷化物之組成、晶面結構與氧化態;將其附載在旋轉電極上並透過三電極系統得知其析氫反應活性。此論文最初以不同金屬磷化物之測試得知磷化鈷之析氫效果最佳，並透過熱處理步驟最佳化磷化物之生成。250 與 350oC 為兩重要溫度，分別生成 PH3和置換氧，能決定性的控制磷化鈷之品質。透過升溫速率和持溫時間能找出適當的磷化鈷生成擁有最佳之析氫反應活性;過短或過長之熱處理步驟皆會導致磷化不完全或過度氧化的問題。因此，此論文找出在升溫速率 5oC/分鐘、持溫時間 250/350oC 在 160 分鐘/2 小時、320 分鐘/2 小時能獲得擁有最佳產氫反應活性之高品質磷化鈷，擁有 59、77 mV/dec 的 Tafel slope 與在-189、191 mV 下達到10 mA/cm2 之效果。另外，改變前驅物使用硝酸鈷能發現氯化物為更好的選擇。

關鍵字

析氫反應 ； 磷化鈷 ； 次亞磷酸鈉 ； 電負度 ； 表面元素比例

並列摘要

Hydrogen evolution reaction (HER) is an efficient method to produce renewable hydrogen fuel and has been extensively studied to fundamentally solve the energetic problems caused from the fossil fuels. The present study aims to optimize the metal phosphide catalysts for the best HER efficiency.
In the synthetic process of metal phosphides starts from the metal oxide (CoO) formation by co-precipitation of metal oxalate and chloride and sintering at 300OC for an hour; the metal phosphides are further fabricated in the solid reaction by controlled heating of mixtures of the synthesized oxides and sodium hypophosphite (NaH2PO2). The fabricated phosphides are then characterized by ICP-MASS, EDX, SEM, XRD and XPS for their compositions, crystal structures and oxidation states; they are loaded onto a rotating disk electrode and examined by a three-electrode system for their HER activity.
Our study initially examined several metal phosphides and found that CoP shows the best HER activity among them. Furthermore, we focused on optimize the heating process for the phosphide formation. Two important temperatures of 250 and 350OC for PH3 formation and reaction with oxide, respectively, decidedly control the quality of CoP. The temperature heating up speed and duration are extensively examined to find proper CoP formation with the best HER activity; shorter or longer heating processes cause insufficient phosphide formation or over oxidation problems. As a result, our study finds that the heating up speed at 5oC/ min and duration of 250/350OC at 160 minutes/2 hours, 320 minutes/2 hours forms the high quality of CoP with the best HER activity of -189, 191 mV in overpotential and 59, 77 mV/dec in Tafel slope. Altered precursor of cobalt nitride is additionally examined and finds that the precursor of chloride is the better choice.

並列關鍵字

Hydrogen evolution reaction(HER) ； Cobalt phosphide ； Sodium phosphinate ； electronnegativity ； surface element ratio

參考文獻

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