低溫還原氧化石墨烯應用於染料敏化太陽能電池對電極之研究

Investigation of Low Thermal Reduction of Graphene Oxide for Dye-Sensitized Solar Cell Counter Electrode

梁淳棨(Chun-Chi Liang)

指導教授 ： 何青原

中原大學/工學院/機械工程研究所/碩士(2015年)

https://doi.org/10.6840/CYCU.2015.00412

摘要

本文使用塊狀石墨透過Hummers法先將石墨塊材剝離成片狀氧化石墨烯(GO)，然後將合成的氧化石墨烯透過化學還原法及熱還原法還原為少層堆疊的石墨烯，最後再以高溫爐管通入氮氣以熱還原的方式還原石墨烯和一般未通入氮氣之熱還原石墨烯比較。還原石墨烯的表面型態、晶相及缺陷狀態分別透過電子顯微鏡、X-射線繞射分析及拉曼光譜和傅立葉轉換紅外光譜佐證。本文使用還原石墨烯應用於染料敏化太陽能電池的對電極，因為石墨烯擁有優異的電荷傳導特性及電解活性且在價格方面比傳統染料敏化太陽能電池的鉑對電極更具優勢，但氧化石墨烯充滿各種結構上的缺陷及氧缺陷，本研究使用熱還原法透過不同還原溫度將缺陷移除，隨著還原溫度增加缺陷逐漸得到改善。此外，透過化學還原法還原之石墨烯屬於非結晶相，因為替代氧離子的Ti+離子擾亂了石墨烯原先的排列。透過電化學阻抗頻譜可以得知較高的還原溫度可以使還原石墨烯的電阻降低進而增長電子的壽命,使用熱還原法還原的石墨烯對電極組裝之染料敏化太陽能電池，其轉換效率可達到3.22 ％，在氮氣環境下還原之石墨烯其轉換效率最高則可達3.318 ％。

關鍵字

氧化石墨烯 ； 染料敏化太陽能電池 ； 熱還原法 ； 化學還原法 ； 電化學阻抗頻譜

並列摘要

Flake-type graphite was used for synthesizing graphene oxide (GO), which was then reduced to a few layers of graphene sheets by using a chemical reduction or thermal reduction method. The thermal reduction method can be divided reduction in the air or nitrogen. The surface morphology, phase crystallization, and defect states of the reduced graphene were determined using electron microscopy and X-ray diffraction and by using Raman and infrared spectra. A dye-sensitized solar cell with the synthesized graphene as the counter electrode was fabricated for evaluating the electrolyte activity and charge transport performance. Intercalated defects that are generally formed during the thermal reduction of GO (tGP) were eliminated by increasing the reduction temperature. Furthermore, the product of the chemical reduction of GO was also in the amorphous phase because substitutional Ti+ ions disrupted the graphene order. Electrochemical impedance spectra showed that increasing the thermal reduction temperature could yield tGP with a lower resistance, increase the electron lifetime, and result in an energy conversion efficiency of approximately 3.22%.Graphene reduction in nitrogen conversion efficiency of approximately 3.318%.

並列關鍵字

graphene oxide ； dye sensitized solar cell ； thermal reduction ； chemical reduction ； electrochemical impedance spectra

參考文獻

[1] K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature, vol. 457, no. 7230, pp. 706-710, 2009.

[2] M. Lotya, Y. Hernandez, P. J. King, R. J. Smith, V. Nicolosi, L. S. Karlsson, F. M. Blighe, S. De, Z. M. Wang, I. T. McGovern, G. S. Duesberg, and J. N. Coleman, “Liquid Phase Production of Graphene by Exfoliation of Graphite in Surfactant/Water Solutions,” Journal of the American Chemical Society, vol. 131, no. 10, pp. 3611-3620, 2009.

[5] W. Gao, L. B. Alemany, L. J. Ci, and P. M. Ajayan, “New insights into the structure and reduction of graphite oxide,” Nature Chemistry, vol. 1, no. 5, pp. 403-408, 2009.

[6] H. M. Ju, S. H. Huh, S. H. Choi, and H. L. Lee, “Structures of thermally and chemically reduced graphene,” Materials Letters, vol. 64, no. 3, pp. 357-360, 2010.

[7] E. Ramasamy, W. J. Lee, D. Y. Lee, and J. S. Song, “Nanocarbon counterelectrode for dye sensitized solar cells,” Applied Physics Letters, vol. 90, no. 17, 2007.