碳材上的磷化二元鎳鈷晶體對於產氫反應之催化效果探討

Abstract

氫氣是一種未來能源的趨勢，可以取代目前在能源上大量使用的石油燃料，在本研究中，我們調整多種的鎳鈷比例 9/1, 5/1, 3/1, 2/1, 1/1, 1/2, 1/3, 1/5, 1/9。研究低成本的鎳鈷磷化物對產氫反應的活性。金屬氧化物利用溶膠凝膠共沉澱法並鍛燒後合成，然後通過化學氣相沉積法製備金屬磷化物。本研究利用能量散射光譜儀(EDX)、高解析耦合電漿光學發射光譜儀(ICP-OES)、X光光電子光譜(XPS)分析催化劑之表面及整體組成，利用X光粉末繞射儀(X-Ray Powder Diffraction analysis, XRD) 、掃描式電子顯微鏡(Scanning Electron Microscope, SEM) 、穿透式電子顯微鏡(Transmission electron microscope, TEM)做晶體結構和表面結構分析。在產氫反應活性的測定，包括過電位和 Tafel 斜率，以及電化學活性表面積由電化學測量確定。本實驗的結果發現，Ni/Co = 1/1 的催化劑具有最好的 HER 活性，Tafel 斜率為 76.8 mV/dec，在-10 mA/cm2時過電位為 93 mV。根據鑑定結果，最好的催化劑Ni/Co=1/1有最大的ECSA為1641 cm2/g，並且樣品保持純Ni2P的晶型下參入Co，可以有效的提升過電位，傾向於 Volmer-Heyrovsky 反應機構並有良好的 Tafel 斜率。Hydrogen is a primosing energy and can replace the limited and polluted fossil fuels in the near futhre. In our present study, we examine hydrogen evolution reaction (HER) on low-cost nickel and cobalt phosphides with various Ni/Co ratios of 9/1, 5/1, 3/1, 2/1, 1/1, 1/2, 1/3, 1/5, 1/9. Metal oxides have been initially synthesized by sol-gel precipitation method. The phosphides were then fabricated by chemical vapor deposition method. The chemical and surface compositions were characterize by EDX, ICP-OES and XPS; crystallines and surface structures were analyzed by XRD, SEM, TEM; finally, the HER activity, including overpotential and Tafel slope, and ECSA were determinined by electrochemical measurements. Our results found that the catalyst with Ni/Co = 1/1 has the best HER activity with Tafel slope of 76.8 mV/dec and overpotential of 93 mV at 10 mA/cm2. According to the characterizations, the best catalyst of Ni/Co=1/1 shows the largest ECSA of 1641 cm2/g，and has the most purified Ni2P phase with Co doping, ,responsible for the lower overpotential, which favors for the Volmer-Heyrovsky mechanism and results the low Tafel slope.