近室壓X光光電子能譜探討鉑負載二氧化鈦單晶(110) 對二氧化碳與水之光催化還原反應研究

Ambient Pressure X-ray Photoelectron Spectroscopy Study of Photoreduction of CO2 with H2O on Pt-loaded TiO2(110)

丁緯(Ting, Wei)

指導教授 ： 楊耀文

國立清華大學/理學院/化學系所/碩士(2019年)

摘要

自工業革命以來，人類活動過度地消耗石化燃料造成大量的溫室氣體和汙染物排放。其中溫室氣體二氧化碳的濃度屢創新高，使得二氧化碳的回收與再利用成為一個重要的議題。對於二氧化碳光催化反應，二氧化鈦為良好的光催化材料，能夠有效地藉由光激發使二氧化碳還原成有經濟價值的物種，且負載金屬做為助催化劑，能夠增加其催化活性。本篇論文主要使用國家同步輻射研究中心台灣光源之近室壓X光光電子能譜實驗站，探討鉑負載二氧化鈦單晶(110) 對二氧化碳光催化還原反應性。鉑負載二氧化鈦單晶(110) 樣品藉由物理氣相蒸鍍技術於超高真空狀態將鉑金屬蒸鍍於二氧化鈦單晶(110) 上，再利用X光光電子能譜做其負載濃度的檢驗。我們透過乾淨的鉑負載二氧化鈦單晶(110) 突破一般催化劑表面有碳污染的限制，並在圖譜觀察到二氧化碳與水的光催化還原反應的數個中間體以釐清其光催化還原途徑。結合臨場近室壓X光光電子能譜與程式升溫反應譜的結果顯示，在臨場近室壓X光光電子能譜中，未負載鉑金屬之單晶在光電子能譜中並未有太大變化，顯示其光催化活性效率不佳；相反的，當負載鉑金屬時顯著地加強其光催化活性，在表面產生更多碳物種，特別是一氧化碳與甲酸鹽物質，最終生成甲烷。光催化反應效率的提升為二氧化鈦受紫外光激發產生的電子能夠有效的的轉移至鉑金屬上，且鉑金屬能有效的吸附一氧化碳，進一步作還原反應。在程式升溫反應譜中我們也能觀察到在鉑金屬負載的二氧化鈦單晶(110) 上產生主要產物甲烷以及次要產物一氧化碳及甲醇。

關鍵字

近室壓X光光電子能譜 ； 二氧化碳 ； 二氧化鈦 ； 光催化反應

並列摘要

Since the industrial revolution, the excessive consumption of fossil fuels by human activities has released an enormous amount of pollutants and greenhouse gases into the atmosphere, resulting in a catastrophic change of our living environment. The problem of ever-increasing CO2 concentration has made the sequestration of CO2 and a conversion of CO2 into useful carbon feedstocks an important issue. TiO2 is a photocatalyst capable of reducing CO2 into low-molecular weight, valuable chemicals under the illumination of solar light. With the addition of noble metals as so-called cocatalysts, the photocatalytic activity is further enhanced. In this thesis, we employ
in-operando Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) technique, recently made available in Taiwan, to investigate the photocatalytic reduction of carbon dioxide on Pt/TiO2(110). The Pt/TiO2(110) photocatalyst was prepared by vapor-depositing Pt atoms on a TiO2(110) single crystal in a UHV chamber, with the amount of Pt film determined by a quartz crystal monitor and later verified by X-ray photoelectron spectroscopy (XPS). By working with the clean, UHV-deposited Pt on rutile TiO2(110) surface, we bypass the severe carbon contamination limitation, commonly encountered when working with catalysts, and identified several surface intermediates that are important in unraveling photoreduction pathway of CO2 with H2O on Pt/TiO2 through a combined APXPS and TPRS studies. APXPS C 1s spectra show that bare TiO2 does not exhibit much photoactivity as judged from the similarity of the spectra taken under various conditions. In contrast, Pt loaded TiO2 surface exhibits a much enhanced photoactivity, producing a few more surface carbon species, in particular CO and formate species, leading to an eventual methane formation. The enhanced photoreduction capability is believed to be due to an increasing availability of electrons migrating to the Pt sites in conjunction with stronger CO adsorption strength enabled by Pt atoms. In the TPRS experiment, major product of CH4 and minor products of CH3OH and CO are observed on Pt/TiO2(110).

並列關鍵字

ambient pressure X-ray photoelectron spectroscopy ； carbon dioxide ； titanium dioxide ； photocatalytic reaction

參考文獻

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