氧化亞銅/石墨烯奈米異質結構之界面載子動力學與光催化特性研究

Abstract

本論文使用光化學反應法，在單一步驟下成功製備氧化亞銅/還原態氧化石墨烯(Cu2O/RGO)的奈米異質結構，藉由改變所加入氧化石墨烯(GO)的濃度，可有效調控成長於RGO表面之Cu2O奈米晶體的數量。由於RGO具有相當高的電子遷移率，因此當Cu2O經由照光激發後，所產生之電子可快速轉移至RGO上，並留下電洞於Cu2O端以達到載子分離的效果。本研究利用染料標的分子，以時間解析螢光光譜探討發生於Cu2O與RGO異質界面間的載子動力學，並研究電子由Cu2O轉移至RGO的速率常數隨著Cu2O /RGO樣品成份之變化關係，實驗結果發現當RGO比例為2.0 wt%時Cu2O /RGO樣品能展現最佳的載子分離效果。將各種樣品應用於可見光催化降解染料分子的實驗中，發現RGO比例為2.0 wt%的Cu2O /RGO樣品亦展現最優異的光催化效率，其光觸媒活性甚至高於相關商用品例如N-doped P-25 TiO2與Cu2O粉末，此結果闡述Cu2O /RGO奈米異質結構應用於相關光電轉換用途的潛力。在回收再利用實驗中發現，Cu2O /RGO樣品經過多次重複使用後依舊能保持相當活性，顯示Cu2O /RGO作為光觸媒使用乃具有長期穩定性。此外，Cu2O /RGO樣品能有效吸收自然界太陽光來進行光催化反應，故可作為發展太陽燃料生產的觸媒選擇。

This work reported the one-step preparation of Cu2O/RGO nanoheterostructures with the photochemical reaction method. By modulating the concentration of GO employed in the reaction, the amount of Cu2O nanocrystals grown on RGO surface can be readily controlled. Because of the considerably high electrical conductivity of RGO, the photoexcited electrons of Cu2O would preferentially transfer to RGO, leaving positively charged holes in Cu2O to achieve charge carrier separation. Time-resolved photoluminescence spectra were collected to quantitatively analyze the electron transfer event between Cu2O and RGO and its dependence on RGO content. Among the different samples tested, Cu2O /RGO sample with RGO content of 2.0 wt% displayed the highest charge separation efficiency, consistent with the result of dye photodegradation experiment. As compared to the relevant commercial products like N-doped P-25 TiO2 and Cu2O powders, the as-synthesized Cu2O /RGO nanoheterostructures exhibited superior photocatalytic performance toward dye degradation under visible light illumination, demonstrating their potential as applied in relevant photoelectric conversion processes. The recycling test reveals that Cu2O /RGO sample could be promisingly utilized in the long-term course of photocatalysis. Furthermore, the result of performance evaluation under natural sunlight shows that the present Cu2O /RGO nanoheterostructures can be used as highly efficient photocatalysts which can effectively absorb solar spectrum for solar fuel generation.