原位傅立葉紅外光光譜輔助分析銅摻雜促進二氧化鈦長效低溫催化氧化一氧化碳與活性位置之研究

一氧化碳催化氧化反應在近年已廣泛被討論，但過去多專注於貴金屬及其超低溫反應，並且其反應機制仍有待商榷。近年研究指出銅基材料對一氧化碳催化氧化具有十分的潛力，而銅在材料中的物理及化學特性在此反應中扮演著至關重要的角色。本研究係利用一步驟氣溶膠輔助自組裝法（AASA）製備高分散性之銅-二氧化鈦微米球用於低溫下一氧化碳催化氧化之研究。X射線光電子能譜（XPS）的分析中指出所製備之材料隨著銅摻雜，觀察到Cu（I）與Ti（III）的存在，可能形成Cu-O-Ti結構。並利用一氧化二氮（N_2O）輔助氫氣程溫還原法（Hydrogen Temperature Programmed Reduction, H_2-TPR）量測，得知材料的銅分散度可高達80%、粒徑僅約1.2 nm及銅的暴露表面積可達550 m^2/gCu。最後結合原位傅里葉變換紅外光譜（in-situ FTIR）分析，觀察到2080，2130與2360 cm^(-1)處具有明顯的吸收峰，分別對應到銅對CO的吸附與CO_2的吸附。並且在250°C下持溫200小時的穩定性評估中，亦表現出極佳的熱催化穩定性。本研究中最重要的發現在於結合H_2-TPR與in-situ FTIR的結果，歸納出以下結論：（1）銅－二氧化鈦具有兩種活性位置（α,β），（2）其作用與溫度（α≤70℃,β≥130℃）呈高度相關性，（3）最後整合以轉換頻率（Turnover Frequency, TOF）總結─少量的α活性位置（Low temperature site）提供了初始反應的活性位置；β活性位置則主導了整體的一氧化碳氧化。

關鍵字

銅－二氧化鈦微米球；熱穩定性；氣溶膠輔助自組裝法；一氧化碳氧化；原位傅里葉紅外光譜

並列摘要

Copper dispersed well on mesoporous TiO_2 spheres prepared by one-step aerosol-assisted self-assembly (AASA) method for carbon monoxide (CO) oxidation at low temperature. X-ray photoelectron spectroscopy (XPS) results indicated that the ratios of Cu(I)/Cu(II) and Ti(III)/Ti(IV) were related to the amount of copper dopant. The introduction of copper probably substituted titanium in the TiO_2 lattice, wherein the structure of Cu-O-Ti formed. The dispersion, size, and surface area of different loadings of copper on TiO_2 were determined by hydrogen temperature programmed reduction (H_2-TPR). The copper dispersion reached 80% with a particle size of 1.2 nm and a surface area of 550 m^2/gCu. With the increase in temperature in the CO oxidation experiment, CO was initially converted at 70°C and completely transformed at 130°C under optimal conditions. On the basis of catalytic oxidation, CO ability was highly related to the reaction temperature in the in situ Fourier-transform infrared spectroscopy (FTIR) spectrum. In the duration test, high CO oxidation reactivity and structural stability of the Cu- TiO_2 microspheres were observed even at 250°C for 200 h. Copper dispersed well into the TiO_2 framework via AASA synthesis; such dispersion provided highly exposed active sites and long-term reactivity due to the suppression of its aggregation during the reaction.

並列關鍵字

Cu/TiO_2 mesospheres ； Stability ； AASA ； CO oxidation ； in-situ FTIR

參考文獻

Creasey, R.C.G.,Mostert, A.B.,Solemanifar, A.,Nguyen, T.A.H.,Virdis, B.,Freguia, S.,Laycock, B.(2019).ACS Omega.4,3159-3168.

Google Scholar

Drozd, G.T.,Zhao, Y.,Saliba, G.,Frodin, B.,Maddox, C.,Weber, R.J.,Chang, M.-C.O.,Maldonado, H.,Sardar, S.,Robinson, A.L.,Goldstein, A. H.(2016).Environ. Sci. Technol..50,13592-13599.