| 摘要: | 本研究探討光化學反應於修復石墨烯缺陷結構的機制與其應用。利用Hummers’法製作氧化石墨烯，接著利用刮刀成膜的方法獲得均勻性的石墨烯薄片，並以氫碘酸做初步的化學還原，最後以聚光型氙燈做光還原，藉由改變反應溫度與照射累積能量來得到光還原的最佳參數。光還原的最佳條件為25 ℃照射3次升溫至50 ℃照射3次，可修復原結構變為高碳氧比(C/O)達36.20、高結晶性(Raman D/G =0.24; Raman 2D/G =0.43)的石墨烯。經過光化學還原的石墨烯，由於高效率的脫氧還原反應，將使結構呈現多孔隙的型貌，其孔隙約300 nm。研究發現，藉由氙燈照射能促進氫碘酸產生光解反應，碘分子幫助打斷C-O鍵結，提高C/O比，而還原過程的放熱反應會藉由連鎖反應向整個材料內部傳遞，此熱能可以進一步的修復缺陷態結構。為了驗證此方法所獲得石墨烯的特性，將應用於超級電容之電極材料上，以6 M KOH作為電解液，經由光還原後的電極材料可得到28 F/g之比電容值，相較於氫碘酸還原後的電極材料只有12 F/g，電容提升率為233%，原因在於所形成的多孔隙結構，使電解液有更多離子傳輸通道，提升其動力學反應。另外本研究也將石墨烯應用於導熱片上，氫碘酸還原後的薄片則表現優良的導熱特性，熱擴散係數439 mm2/s、熱傳導係數1056 W/m．K，原因在於其緊密的堆疊結構、低孔隙率、減少缺陷，有利於導熱片利用之需求。本研究為一種快速且高效率還原與修復氧化石墨烯的方法，未來將能對高品質石墨烯生產與應用有所助益。;In this study, we investigate the mechanism and applications of the restoration on reduced graphene oxide(rGO). Here, graphene oxide(GO) paper is prepared by a Hummers’ method and doctor blade coating, followed by chemical reduction by using Hydroiodic acid(HI) for preliminary reduction. Finally, the photoreduction was carried out to further restore graphene by using light-focusing Xenon flash lamp. The optimized condition of photo reduction was obtained by controlling temperature and flash shot. The optimized parameters to restore graphene are subjected to 3 flash shots at 25 ℃, followed byand ramping to the 50 ℃ for additional 3 shots. The resultant rGO shows high C/O ratio(36.2) and high crystalline(Raman D/G ratio=0.24; 2D/G ratio=0.43). Due to the high efficient deoxygenation by photoreduction, the as-prepared rGO paper exhibits porous structure, where the pore size was about 300 nm in average. The study suggest that the comprising of HI chemical treatment and Xenon flash facilitate the photolysis reaction of iodic molecular, leading to high efficient break of epoxy bond (higher C/O ratio). Meanwhile, the exothermic heat during GO reduction process a chain reaction, where heat was found to propagate over whole material, thus further restore graphene defects.
To evaluate the performance and particle application, the as-prepared rGO paper with various reduction conditions were employed as electrodes in a symmetric type supercapacitors by selecting 6 M KOH as electrolyte. The rGO treated by comprising of HI and Xenon flash (rGO-HI-Xe) shows higher specific capacitance of 28 F/g, which was 233% increased when compare to that (12 F/g) of rGO treated by HI(rGO-HI). This was attributed to high specific surface area and diffusion path created from porosity and fluffy structured rGO-HI-Xe samples, thus promoting ion transport capability. In addition, the rGO paper can be utilized as thermal pad. The rGO-HI samples show a thermal diffusivity and thermal conductivity of 439.18 mm2/s and 1056 W/m．K, respectively. The requirements for high performance thermal pad including high density of stacking structure, low porosity and defect density. This work provides a facile and high efficiency method for graphene restoration, which was potential for high quality graphene production and its related applications. |
