產氫催化反應在鎳摻雜磷化鐵的活性探討
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2023
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氫氣是一種具有高能量且環保的可再生能源，能夠代替目前被廣泛使用的化石燃料，是非常具有潛力的新興能源。在沒有使用Pt的產氫反應催化劑中，過渡金屬磷化物中的磷化鐵是一種在產氫反應(HER)中具有潛力的材料，但是磷化鐵的效果遠遠落後Pt。因此本實驗利用硫酸亞鐵與草酸進行共沉澱法後進行鍛燒合成出氧化鐵，再利用化學氣相沉積法(Chemical Vapor Deposition)將磷附著在氧化鐵上以達到磷化來產生磷化鐵，並且摻雜鎳以產生二元磷化物(NixFe1-x)P，透過改變鎳與鐵的比例與不同的氧化溫度造成的電催化活性效果變化。鑑定催化劑方面使用掃描式電子顯微鏡(SEM)進行形貌鑑定，使用粉末X射線繞射儀(PXRD)進行結構鑑定，使用能量色散X射線儀(EDX)以及X射線光電子譜儀(XPS)鑑定催化劑組成，電催化活性方面使用線性伏安法(LSV)獲得過電位(overpotential)以及塔菲爾斜率(Tafel slope)，使用循環伏安法(CV)測量活性面積獲得雙電層電容值(Cdl)。最後結果能夠發現將鎳摻雜進磷化鐵中可以增強磷化鐵的電催化效果以及活性位點，並調整鎳摻雜比例到33%時，形成(NiFe¬2)P，有著最好的電催化活性，另外改變氧化溫度也會影響電催化活性，當氧化溫度提升至500度時，(NiFe¬2)P-500顯示出最好的電催化效率，在-10 mA/cm2時的過電位為115 mV，Tafel slope為81 mV/dec，所以在這催化劑中，HER機制屬於Volmer-Heyrovsky mechanism。
Hydrogen fuel, a high-energy and environmentally friendly renewable energy, that has been widely utilized in some applications, and can replace the limited and polluted fossil fuels. Hydrogen evolution reaction (HER) is a promising electrochemical process that can efficiently produce hydrogen without green-house gas emission. Furthermore, utilizing transition metal phosphides to replace costly Pt can economically push HER to the practical applications.In the present study, we used co-precipitation method of ferrous sulfate and oxalic acid to synthesize iron oxide; chemical vapor deposition method is then employed for phosphating the oxide to produce iron phosphide. To further improve the HER activity, and nickel is introduced to form binary phosphide, (NixFe1-x)P. The catalytic activity varies with the compositions and oxidation temperatures has been systematically examined to achieve the best HER performance. Samples were characterized by Scanning Electron Microscope (SEM) was used for morphology, Powder X-ray Diffractometer (PXRD) for structure, Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) for catalyst composition. The electrocatalytic activity were examined by, Linear Sweep Voltammetry (LSV) to obtain overpotential (η10) and Tafel slope; Electrochemical Active Surface Area (ECSA) was determined by Double Layer Capacitance (Cdl) in Cyclic Voltammetry (CV). Our result found that doping nickel into iron phosphide can enhance activity of iron phosphide; the best doping ratio is 33% in the formation of (NiFe2)P. Also, oxidation temperature also can alter the catalytic activity and the best one is at 500 ℃ with the overpotential of 115 mV at -10 mA/cm2 and Tafel slope of 81 mV/dec. Accordingly, HER follows Volmer-Heyrovsky mechanism on those phosphide catalysts.
Hydrogen fuel, a high-energy and environmentally friendly renewable energy, that has been widely utilized in some applications, and can replace the limited and polluted fossil fuels. Hydrogen evolution reaction (HER) is a promising electrochemical process that can efficiently produce hydrogen without green-house gas emission. Furthermore, utilizing transition metal phosphides to replace costly Pt can economically push HER to the practical applications.In the present study, we used co-precipitation method of ferrous sulfate and oxalic acid to synthesize iron oxide; chemical vapor deposition method is then employed for phosphating the oxide to produce iron phosphide. To further improve the HER activity, and nickel is introduced to form binary phosphide, (NixFe1-x)P. The catalytic activity varies with the compositions and oxidation temperatures has been systematically examined to achieve the best HER performance. Samples were characterized by Scanning Electron Microscope (SEM) was used for morphology, Powder X-ray Diffractometer (PXRD) for structure, Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) for catalyst composition. The electrocatalytic activity were examined by, Linear Sweep Voltammetry (LSV) to obtain overpotential (η10) and Tafel slope; Electrochemical Active Surface Area (ECSA) was determined by Double Layer Capacitance (Cdl) in Cyclic Voltammetry (CV). Our result found that doping nickel into iron phosphide can enhance activity of iron phosphide; the best doping ratio is 33% in the formation of (NiFe2)P. Also, oxidation temperature also can alter the catalytic activity and the best one is at 500 ℃ with the overpotential of 115 mV at -10 mA/cm2 and Tafel slope of 81 mV/dec. Accordingly, HER follows Volmer-Heyrovsky mechanism on those phosphide catalysts.
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Keywords
產氫反應, 過渡金屬磷化物, Hydrogen evolution reaction, Transition Metal Phosphides