石墨烯-鈦酸鹽奈米異質結構應用於光催化甲醇燃料電池

Abstract

本論文使用水熱法，在單一步驟下成功製備鈦酸鹽/還原態氧化石墨烯(titanate /RGO)奈米異質結構，藉由改變所加入氧化石墨烯(GO)的濃度，可有效調控成長於石墨烯(RGO)表面之TiO2奈米管的數量。由於RGO具有相當高的電子遷移率，因此當titanate 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titanate 端以達到載子分離的效果。為了評估樣品之光轉化效率，本研究將各種不同titanate /RGO比例之樣品製作成陽極，並於電化學系統中量測甲醇氧化反應特徵電位與相對應電流值，比較實驗數據後發現titanate /RGO樣品能展現優異的光催化甲醇氧化效果，將樣品之甲醇氧化電流數值與titanate 奈米管樣品之數值做比較，其差異值可高達3.7倍。若將白金奈米顆粒黏附上titanate /RGO後，該樣品之甲醇氧化電流數值除以白金的負荷重量(記作一單位負荷重的白金所導致之電流數值A/mgPt)與商用品催化劑Pt/C之數值的差異值可高達4.7倍。此結果闡述titanate /RGO奈米異質結構作為甲醇氧化反應之光觸媒用途的潛力，可望應用於各種光電化學電池與光輔助燃料電池之觸媒層。

In this work, we reported the one-step preparation of titanate /reduced graphene oxide nanoheterostructures with a facile hydrothermal method. The samples were prepared by reacting graphene oxide (GO), which was obtained from Hummers’ method, with P-25 TiO2 nanoparticles in the alkaline hydrothermal reaction. During the hydrothermal process, reduction of GO was accompanied with the deposition of titanate nanotubes, resulting in the formation of titanate /RGO nanoheterostructures. Because of the considerably high electrical conductivity of RGO, the photoexcited electrons of titanate nanotubes would preferentially transfer to RGO, leaving positively charged holes in titanate to achieve charge carrier separation. To evaluate the photoconversion efficiency, the samples were used as photoanode in the half-cell reaction of direct methanol fuel cell and measured with cyclic voltammetry. As compared to the pristine titanate nanotubes, titanate /RGO samples displayed 3.7-fold enhancement in photocurrent generation under white light illumination. A 4.7 times increase in methanol oxidation current was attained by RGO-TNT-Pt, demonstrating its promising potential in relevant photo-assisted fuel cells.