| 摘要: | 環境議題在近幾年已逐漸浮現，為了要減輕全球暖化以及能源短
缺，電化學還原二氧化碳以及電解水產氫這些技術正在逐漸發展中，
然而尚有許多問題等待克服，像是二氧化碳還原的產物選擇率低和缺
少無白金的高效能電催化析氫觸媒，在本研究中利用化學還原法製備
出不同比例的碳支撐鈀銅觸媒分別命名為Pd, Pd70Cu30, Pd50Cu50,
Pd25Cu75 應用在二氧化碳電化學還原以及電催化析氫，同時這些觸媒
也利用熱處理改質以改善催化效能，所製備觸媒之結構、表面組成、 化學組成、形貌、電化學、以及電化學的氣相產物分析可藉由X 光繞
射儀(X-ray diffraction, XRD) 、光電子能譜儀(X-ray photoelectron spectroscopy, XPS)、感應耦合電漿原子發射光譜分析儀(inductively
coupled plasma-optical emission spectrometer, ICP-OES)、高解析度穿透
式電子顯微鏡(high resolution transmission electron microscopy,
HRTEM)、電化學量測系統，以及氣相層析儀(Gas chromatography, GC)
等儀器鑑定。
本研究分為兩個部分，第一部分以油胺還原出不同比例的碳支撐
鈀銅觸媒，在鈀中添加適量的銅可以促進CO2 還原中CO 的選擇性，
由於Pd 和Cu 的協同作用，Pd 的d-band 中心降低，中間物的化學吸
附能減弱，從而提高CO2 還原性能，在-1 V 下CO 法拉第效率為79
%。然而在析氫反應中，和不同比例的鈀銅觸媒做比較，Pd 有著最佳
的過電位和塔佛斜率，代表銅的添加對鈀之析氫反應沒有正面的效應。
第二部分碳支撐觸媒藉由空氣熱處理改質，除了Pd 以外，鈀銅
材料在析氫反應的結果有顯著的改善，在XPS 的分析中，觸媒在熱處理過後可以觀察到銅的表面偏析以及氧化，此兩種改質促進了析氫
的效能，特別是Pd70Cu30經過熱處理後 (-52 mV)有著優於Pd (-61 mV)
的過電位，同時也接近於白金商用材的結果(-38 mV)。;In order to reduce global warming and develop the renewable energy, electrochemical CO2 reduction and water splitting for hydrogen production have been developed to solve these issues. However, there are still a lot of problems to overcome, such as low selectivity for CO2 reduction reaction (CO2RR) and lack of Pt-free highly efficient catalyst for hydrogen evolution reaction (HER) activity. In this study, carbon-supported PdxCu100-x with different compositions including Pd, Pd70Cu30, Pd50Cu50, and Pd25Cu75 with or without heat treatments have been prepared for CO2RR and HER. The phases and structures, surface compositions, chemical compositions, morphologies, electrochemical properties and the gas product of prepared catalyst are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometer (ICP-OES), high resolution transmission electron microscope (HRTEM), rotating disk electrode (RDE) and gas chromatography (GC), respectively.
This study is divided into two parts. In the first part, carbon-supported PdxCu100-x nanoparticles (NPs) have been prepared. The alloying of Cu into Pd demonstrates great promotion in the selectivity of CO towards CO2 reduction. Due to the synergistic effect of Pd and Cu, the d-band center of Pd is lowered and the chemisorption energy of intermediate is weakened, thereby enhancing the CO2RR performance with a CO Faradaic efficiency
of 79% at -1 V. However, for HER, in comparison with other PdxCu100-x NPs, Pd shows the lowest overpotential and tafel slope, indicating that
alloying Cu into Pd did not have positive effect on the HER performance.
For the second part, carbon-supported PdxCu100-x NPs have been heat
treated under air atmosphere. After the air heat treatment, except Pd the
HER results of PdxCu100-x NPs have been significant improved. Based on
XPS characterization, surface Cu segregation is observed on the catalyst
after the air heat treatment, which may promote the HER performance,
especially Pd70Cu30-HT, which shows better overpotentials (-52 mV) than
Pd (-61 mV) and close to Pt commercial (-38 mV). |
