碳支撐銅銀核殼奈米觸媒於電化學二氧化碳還原反應效能之研究

The Electrochemical CO2 Reduction Reaction on Carbon-Supported Cu-Ag Nanocatalysts with Core/Shell Structures

賴勇達(Lai Yong-Da)

指導教授 ： 王禎翰

國立臺灣師範大學/理學院/化學系/碩士(2020年)

https://doi.org/10.6345/NTNU202000557

摘要

電化學二氧化碳還原反應為二氧化碳排放與近年來的再生能源提供有效的解決方案，透過再生能源產生的能源將二氧化碳轉換成高價值的化學燃料，使大氣中碳循環能維持在定值中。目前已有許多對於不同催化材料的研究，其中金屬奈米觸媒已有豐富的研究對於其選擇性與效能。
本研究探討使用油胺法進行合成銅銀合金觸媒，利用能量色散X射線光譜(EDX)、電感耦合電漿體原子發射光譜(ICP-OES)、粉末式X光繞射分析儀(XRD)、X光光電子光譜儀(XPS)和反應活性面積(ECSA)檢測晶體結構、金屬價態與觸媒金屬表面比例。電化學實驗以線性掃描伏安法(LSV)、一氧化碳脫附測試(CO stripping)和二氧化碳還原效能測試檢測對反應中的吸脫附機制和產物的選擇性。在ICP-OES與ECSA的測量中，可以得到觸媒的總金屬比例與表面金屬比例差異，確認觸媒為核殼結構。在電化學測試可以發現在-0.8 V (vs.RHE)時CuAg-180/C擁有84% CO選擇性，因在二氧化碳活原反應的觸媒中，Cu比Ag的還原性更好，但容易將二氧化碳進行深度還原，還原成碳氫產物和多碳產物，在Cu表面添加Ag可以降低Cu對CO的吸附能，使還原步驟在中間產物CO就脫附，來提高觸媒為CO的選擇性；而CuAg1.5-200/C在-0.9 V(vs. RHE)下有89% CO選擇性，從ECSA與XRD上可以看出此觸媒類似Ag奈米粒子，而Ag對CO本來就具有高選擇性。

關鍵字

銅銀奈米觸媒 ； 二氧化碳電化學還原 ； 法拉第效率 ； 核殼奈米觸媒 ； 銅銀雙金屬效應

並列摘要

The electrochemical carbon dioxide reduction reaction (CO2RR) provides an effective solution to remove the problematic carbon dioxide and produce useful high-value chemical fuel. The present thesis focused on examining the core-shell structured Cu-Ag bimetals with the best CO2RR performance. The catalysts were synthesized by oleyamine method and optimized with synthetic temperatures (150, 180, 200 and 220oC) and Cu/Ag ratios (0.5, 1 and 1.5). The synthesized samples were characterized by energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction analyzer (XRD), X-ray photoelectron spectrometer (XPS) and Electrochemical Catalyst Surface Activity (ECSA); the electrochemical performance were examined by linear scanning voltammetry (LSV) and carbon monoxide desorption test (CO stripping); the products after electrochemical reactions were detected by gas chromatograph (GC) to analyze the Faradic Efficiency (FE) and CO2RR performance. In the electrochemical tests found that that the optimal synthetic temperature of Ag shell is at 180 oC with 84% CO FE at -0.8 V (vs. RHE) due mainly to the higher Ag ratio of Ag(110)/ Ag(111) on the surface and adding Ag on the surface of Cu can reduce the binding energy of Cu to CO, so Cu can desorb CO to improve the CO selectivity. Also, directly adding more Ag in the formation of CuAg1.5-200/C can further enhance the performance with 89% CO selectivity at -0.9 V (vs. RHE) from ECSA and XRD that CuAg1.5-200/C is similar to Ag nanoparticle has high CO selectivity. The results demonstrated that more surface Ag in the CuAg bimetals can effective enhance the CO2RR performance and provide the useful information for better design the optimal CO2RR catalysts.

並列關鍵字

CuAg nanocatalysts (CuAg NCs) ； CO2 reduction reaction (CO2RR) ； faraday efficiency (FE) ； core-shell nanocatalysts ； CuAg bimetallic effect

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