合成高導電石墨烯材料作為染料敏化太陽能電池電極之研究

Synthesis of highly conductive graphene materials for dye-sensitized solar cells counter electrode

鍾永彬(Yung-Pin Chung)

指導教授 ： 王宏文

中原大學/理學院/化學研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200516

摘要

本實驗利用氧化石墨法製備石墨烯薄膜對電極，首先把多層堆疊的石墨以硫酸和過錳酸鉀氧化24小時。當氧化時，原本sp2的多層石墨結構會轉為sp3，造成層與層間的分離。氧化完成用冷凍乾燥法乾燥成粉末後添加高分子聚合物當作黏結劑進行漿料配製，之後塗抹於玻璃基板上，用熱處理法在650℃將氧化石墨還原成石墨烯。在黏結劑選擇方面利用PEG(Polyethylene glyco)、PEO(Polyethylene oxide)、PVP(Polyvinylpyrrolidone)和Terpineol(松油醇)來做測試。結果顯示PEG製成的薄膜可做到較低電阻，透光率也比其他三種黏結劑高，效率測量結果PEG有最接近白金對電極相近度約85 %，後面漿料調配皆以PEG作Binder。
最初本研究所得之石墨烯薄膜電阻大約在100 ~ 30 Ω/sq，其效率與白金電極比較只有50%。為了降低電阻值，減少溶劑量並使固含量提升。當滴入電解質後，薄膜會與基板不穩造成起伏分離。推測應是石墨烯薄膜的穩定性與基板的附著力有關，薄膜與基板的凡得瓦爾力被破壞，伏起的薄膜介面電阻過大導致電池運作時電子無法順利的傳遞，或是薄膜接觸到工作電極造成短路。為了改善石墨烯電極的表面性質使介面間阻抗下降及薄膜與基板的附著力，利用陰陽離子聚合物對玻璃基版做處理來增加薄膜與基板的附著力，也利用增加膜厚度來降低薄膜電阻值。數據結果顯示薄膜電阻可降低至5 ~ 10 Ω/sq，而效率與白金電極相比可達到九成相似甚至超越一些。
使用膠態電解質來改善液態電解質組裝成DSSC會發生的問題，但是效率卻沒有比液態電解質好。使用自製工作電極其效率可以高出商用工作電極許多，配合液態與膠態電解質測量石墨烯對電極，最後結果是自製工作電極與液態電解質測量石墨烯對電極之效率為最好。最後在氧化還原能力中石墨烯雖然沒有比白金好，但是因為氧化還原反應在碎片邊緣處，而整個薄膜是由許多碎片堆疊而成，造成能氧化還原電子的量就變多。綜合上述結果其石墨烯替代能力能與白金相當，達到取代導電玻璃的目標又更進一步。

關鍵字

石墨烯 ； 對電極

並列摘要

In this study, preparation of graphene thin film electrode through graphite oxide was studied. First, multi-layer stacking of graphite was oxidized using sulfuric acid and potassium permanganate for 24h. After oxidation, the solids obtained were dried by freeze-drying and coating on glass substrate, then heat treatment at 650 oC was used to reduce the GO to graphene. PEG, PEO, PVP, Terpineol were used as the binder for reforming graphene into films. It shows that the PEG-made film achieves lower resistance, higher light transmittance than those of the other three binders. The efficiency of DSSC using PEG-made grahene electrode is around 85% of those using Pt-based electrode.
At the beginning of this study, the thin-film resistance of graphene electrode is about 100-30 Ω/sq, The graphene was also suffered from the electrolyte, that is the film and substrate will be unstable when liquid electrolyte was present. When the glass substrate was modified using some polyelectrolytes, the resistance of graphene films go down to 5-10 Ω/sq. In the mean time, the efficiency of DSSCs using the modified graphene film electrode can achieve 90% of those using Pt-based electrode or even better. Finally, the catalytic ability of graphene, though is no better than platinum, there edges result more amount of the catalytic sites for electron transfer. Taking these results into account, the catalytic capability of graphene can be quite compatible to that of platinum, making this material a good alternative to platinum as a counter electrode for a high performance DSSC.

並列關鍵字

counter electrode ； graphene

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