鎳鐵金屬有機骨架/鎳鐵氧化物混成電催化材料於鹼性電解水之應用

Abstract

本研究提出一種電催化層的製造方法，可將鎳鐵金屬有機骨架與鎳鐵氧化物之混成材料以水熱法生長在碳紙上，並應用於鹼性電解水系統中。本研究製成的鎳鐵金屬有機骨架電催化層，經由X射線光電子能譜儀(XPS)可證實鎳與鐵材料被生長在碳紙上，並由場發射掃描式電子顯微鏡(SEM)顯示其材料附著狀況，X射線繞射儀(XRD)顯示一8.8°之繞射峰，為金屬有機骨架之結構，其餘材料主要為鎳鐵氧化物。 在電解系統測試中，陽極與陰極皆使用鎳鐵電催化層之系統命名為NiFe(+)/NiFe(-)，本研究亦單獨置換陰極電催化層為釕電催化層，命名此系統為NiFe(+)/Ru(-)，藉此比較貴金屬與非貴金屬的性能差異。在電流密度500 mA/cm2下，NiFe(+)/Ru(-)系統的核心電壓為1.79 V，功耗效能比為每立方公尺氫氣消耗4.9度電，能量效率為66.2%。相比之下，NiFe(+)/NiFe(-)系統的核心電壓為2.23 V，功耗效能比為每立方公尺氫氣消耗5.7度電，能量效率為56.6%。經由排水集器法測試系統氫氣之產率，NiFe(+)/Ru(-)與NiFe(+)/NiFe(-)系統的法拉第效率均在96%以上，表示系統幾乎無其他副反應或者漏電流。在電流密度400 mA/cm2的長時間測試中，經過150小時後，NiFe(+)/Ru(-)的核心電壓增加了0.167 V，而NiFe(+)/NiFe(-)的核心電壓下降了0.01 V，在長時間運轉下沒有衰退，證明鎳鐵材料電催化層有良好的穩定性，可做為低成本且易於製造的電催化層使用。

The hydrothermal method is used to grow NiFe metal-organic frameworks (MOFs) and NiFe2O4 on carbon paper (CP) to serve as electrocatalysts in an alkaline electrolyzer. The NiFe metal-organic framework electrocatalyst prepared in this study can be confirmed by X-ray photoelectron spectroscopy (XPS) that nickel and iron materials are grown on carbon paper, and the morphology of the electrocatalyst is shown by field emission scanning electron microscope (FE-SEM). X-ray diffractometer (XRD) shows a diffraction peak of 8.8°, which is the structure of metal organic framework. In the electrolysis system test, the system using NiFe electrocatalyst on both the anode and the cathode was named NiFe(+)/NiFe(-). In order to compare the performance difference between noble metals and non-noble metals, the cathode catalytic layer was replaced by a ruthenium electrocatalyst, and the system was named NiFe(+)/Ru(-). Results show that the current density reaches 500 mA/cm2 at a cell voltage of 1.79 V, with a specific energy consumption of 4.9 kWh/m3 and energy efficiency of 66.2% when using NiFe(+)/Ru(-). However, when using NiFe(+)/NiFe(-), the current density reaches 500 mA/cm2 at a higher cell voltage of 2.23 V, with a specific energy consumption of 5.7 kWh/m3 and energy efficiency of 56.6%. The Faradaic efficiency is high for both setups, ranging from 96% to 99%, indicating that there were almost no other side reactions or leakage currents in the system. After conducting a 150-hour test with a fixed current density of 400 mA/cm2, the cell voltage increases by 0.167 V for NiFe(+)/Ru(-), while it decreases by only 0.010 V for NiFe(+)/NiFe(-), which proves that the electrocatalyst of NiFe material has good stability, and can be used as a low-cost and easy-to-manufacture electrocatalyst.