金/銀奈米島狀薄膜的電漿子增強光催化二氧化碳還原的研究

Abstract

摘要 近年來全球暖化日益嚴重，其中二氧化碳是溫室效應的重要因素之一，因此封存二氧化碳以降低大氣中的二氧化碳濃度，成為人類近年來的重要課題。利用太陽光的能量，在光催化劑上驅動二氧化碳轉化為可再生能源，提供了一個環保且永續的策略。目前以半導體氧化物為主的光催化劑已經有許多文獻發表，但受限於有限的光譜吸收範圍，使其光催化效率有所耗損。由近期的文獻可知，使用貴金屬作為光催化劑，可以產生如甲烷、乙烷、丙烯等碳氫化合物，使其在光催化的領域上逐漸嶄露頭角，成為具有潛力之光催化劑，但其產率及選擇率仍有很大的進步空間且對於反應機制了解有限。本篇材料使用晶種成長法製備金奈米島狀薄膜(Au nanoisland films, Au-NIFs)以及銀奈米島狀薄膜(Ag nanoisland films, Ag-NIFs)。由於金屬奈米材料具有強烈的表面電漿共振(Localized surface plasmon resonance, LSPR)效應，可提升光催化活性，增強二氧化碳還原反應(CO2 reduction reaction, CO2RR)。本篇將Au/Ag-NIFs生長於ITO玻璃上，研究其光催化效果，並進一步藉由控制gap distance的大小，分析金屬奈米島狀結構，以探討對還原產物的選擇性及產率的影響。由光催化結果可得知，Au-NIFs的gap生成可以促進CH4形成，而island及nanoparticles (NPs) (不同Ag-NIFs的生長狀態)之光催化效果分別與gap length和gap distance關係呈正相關。另一方面，與Au-NIFs相比，Ag-NIFs具有較高的CH4產率及選擇性，且Ag NPs 較Ag-NIFs可能更適合用於CH4的CO2RR。由實驗結果可知，Au/Ag-NIFs的生成可以提升CO2RR光催化效果。未來期許本實驗所製備之材料可應用於光電催化二氧化碳還原領域。Abstract Recently, global warming has become a big problem, in which carbon dioxide is one of the main factors of the greenhouse effect. The technique of carbon dioxide fixation for the reduction of carbon dioxide levels in the atmosphere has become a major issue. The application photocatalysts provides an environmentally, friendly, and sustainable strategy, which uses solar energy to drive the CO2 reduction reaction into renewable structure. So far, many studies of photocatalysts based on semiconductor oxides have been published. However, the photocatalytic efficiencies are hindered due to their limited light source absorption capacity in the visible wavelength range. According to recent literature, noble metals can effectively produce hydrocarbons such as methane, ethane, propylene, which make them become the potential photocatalysts. Nevertheless, the application of noble metals in the field of photocatalysisis impeded by the limited photocatalytic efficacy and product selectivity, and the restricted understanding of mechanism. In the study, Au/Ag-NIFs were fabricated by seed-mediated growth. The strong LSPR effect of metallic nanomaterials can improve photocatalytic activity and promote the CO2 reduction reaction. We used ITO glass as the substrates for the fabrication of Au/Ag-NIFs to explore the photocatalytic effect. The effect of metal nanoisland structures and the influence of different distances on the photocatalytic reduction products were further analyzed. Based on the results of Au-NIFs, the generation of gap can promote the formation of CH4. The product yield of CO2RR of island and NP (the growth condition of Ag-NIFs) are positively correlated with gap length and gap distance, respectively. Furthermore, Ag-NIFs has a higher yield and selectivity of CH4. Besides, Ag NPs revealed the better photocatalytic production of CH4 than Ag-NIFs. According to the photocatalytic results, the Au/Ag-NIFs can significantly promote the photocatalytic effect. In the future, we believe the metallic NIFs can be further applied to the photoelectric catalytic CO2RR.