二維石墨烯是目前已知電阻最小及導電性最佳的材料，且能在奈米級的原子層厚度內展現絕佳的電子傳輸特性。本論文透過驅動電解液流經石墨烯薄膜發電進行收集藍色能源之可行性研究，主要目的為提升電極與石墨烯晶片之間的接觸效能並分析誘導電壓。首先，固定傾斜角度下，每分鐘流量越多，初始流速越快，所產生之誘導電壓值越高；固定流量下，當傾斜角度從20˚提升到45˚，重力沿著斜坡的效果明顯，充放電時間相同，流速增加，整體平均電壓上升，然而傾斜角度提升到60˚時，流速提高導致液滴寬度變窄，電壓明顯下降。不同電解液濃度下，誘導電壓先隨電解液濃度成比例上升接著呈飽和狀態，然而當濃度大於特定值時，電雙層厚度變薄，陰陽離子容易結合成電中性的分子而屏蔽電荷，降低輸出電壓。當石墨烯接觸到低溫的電解液時，固液界面的自由度降低，偽電容能更完整地傳輸電子，能誘導出更高的電壓。綜合以上實驗結果可以適用於開發在雨水及海水能量收集，且於低溫且不易下雨之區域提高海水發電效益，廣泛發展藍色能源收集能量之研究。

Graphene is a two-dimensional material with nanometer atomic layer thickness and exhibits excellent physical characteristics such as high conductivity and mechanical strength. In this study, we intend to collect energy from different concentration of NaCl electrolyte droplet flowing over graphene film. A platform with different inclined angles (20˚ ~ 60˚) are used to place the graphene film. Two electrodes attached to the long side of the graphene film are used to measure the induced voltage. It is found that at 45˚ induces the highest voltage. However, when the inclined angle increases to 60˚ the induced voltage decreases significantly due to the droplet exhibits narrower width. Different electrolyte concentration induces different voltage. In general, the induced voltage is proportional to the increase of the concentration until the saturated level at 0.6 M. Further increasing the concentration will yield the thickness of the electric double layer thinner, and resulting the anions and cations combining into electrically neutral molecules to screen the charge of the droplet. Therefore, the induced voltage would decrease more even further increasing the concentration. We also investigate the effect of the temperature of the electrolyte on the induced voltage. It is found that the lower temperature induces higher voltage. Overall, this work shows the feasibility to harvest energy from electrolytes, such as seawater (NaCl) and the parameters affecting the performance of the design setup.

[1] K. S. Novoselov A.K.G., S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva and A. A. Firsov, Electric Field Effect in Atomically Thin Carbon Films. 306: p. 666-669. (2016)
[2] Castro Neto A.H., Guinea F., Peres N.M.R., Novoselov K.S., and Geim A.K., The electronic properties of graphene. Reviews of Modern Physics. 81: p. 109-162. (2009)
[3] Wang X., Zhi L., and Müllen K., Transparent, conductive graphene electrodes for dye-sensitized solar cells. Nano Letters. 8: p. 323-327. (2008)
[4] Shao Y., Wang J., Wu H., Liu J., Aksay I.A., and Lin Y., Graphene based electrochemical sensors and biosensors: A review. Electroanalysis. 22: p. 1027-1036. (2010)
[5] Geim A.K. and Novoselov K.S., The rise of graphene. Nanoscience and Technology: A Collection of Reviews from Nature Journals. p. 11-19. (2009)
[6] Lee C., Wei X., Kysar J.W., and Hone J., of Monolayer Graphene. 321: p. 385-388. (2008)
[7] Bolotin K.I., Sikes K.J., Jiang Z., Klima M., Fudenberg G., Hone J., Kim P., and Stormer H.L., Ultrahigh electron mobility in suspended graphene. Solid State Communications. 146: p. 351-355. (2008)
[8] Murali R., Brenner K., Yang Y., Beck T., and Meindl J.D., Resistivity of graphene nanoribbon interconnects. IEEE Electron Device Letters. 30: p. 611-613. (2009)
[9] Balandin A.A., Ghosh S., Bao W., Calizo I., Teweldebrhan D., Miao F., and Lau C.N., Superior thermal conductivity of single-layer graphene. Nano Letters. 8: p. 902-907. (2008)
[10] Ji X., Xu Y., Zhang W., Cui L., and Liu J., Review of functionalization, structure and properties of graphene/polymer composite fibers. Composites Part A: Applied Science and Manufacturing. 87: p. 29-45. (2016)
[11] Nair R.R., Blake P., Grigorenko A.N., Novoselov K.S., Booth T.J., Stauber T., Peres N.M.R., and Geim A.K., Fine structure constant defines visual transparency of graphene. Science. 320: p. 1308. (2008)
[12] Han T.H., Lee Y., Choi M.R., Woo S.H., Bae S.H., Hong B.H., Ahn J.H., and Lee T.W., Extremely efficient flexible organic light-emitting diodes with modified graphene anode. Nature Photonics. 6: p. 105-110. (2012)
[13] Concerning D., New T., Crew H., Salvio A.D., Jackman T.R., Larson A., Queiroz K., Protas M., Grant B.R., Grant P.R., Tabin C.J., Orgogozo V., Goff L.L., Enders L.S., Werren J.H., Loehlin D.W., Crotty D.A., Gann A., Spring C., Qureshi I., Werren J.H., Murphy M.W., Bardwell V.J., Zarkower D., Arbeitman M.N., Rosler K.M., Harrison D.A., Zeidler M.P., Brown S., Zeidler M.P., Zeidler M.P., Vaughan A.G., Knapp J.M., Baker B.S., Koshikawa S., Williams T.M., Carroll S.B., Rose D.J., and Moczek A.P., References and Notes 1. 335: p. 947-951. (2012)
[14] Wang Y., Shi Z., Huang Y., Ma Y., Wang C., Chen M., and Chen Y., Supercapacitor devices based on graphene materials. Journal of Physical Chemistry C. 113: p. 13103-13107. (2009)
[15] Choudhuri I., Bhauriyal P., and Pathak B., Recent Advances in Graphene-like 2D Materials for Spintronics Applications. Chemistry of Materials. 31: p. 8260-8285. (2019)
[16] Yin J., Zhang Z., Li X., Zhou J., and Guo W., Harvesting Energy from Water Flow over Graphene? (2012)
[17] Ho Lee S., Jung Y., Kim S., and Han C.S., Flow-induced voltage generation in non-ionic liquids over monolayer graphene. Applied Physics Letters. 102. (2013)
[18] Tsai S.J. and Yang R.J., Bimodal behaviour of charge carriers in graphene induced by electric double layer. Scientific Reports. 6: p. 1-7. (2016)
[19] Kwak S.S., Lin S., Lee J.H., Ryu H., Kim T.Y., Zhong H., Chen H., and Kim S.-W., Triboelectrification-Induced Large Electric Power Generation from a Single Moving Droplet on Graphene/Polytetrafluoroethylene. ACS nano. 10: p. 7297-302. (2016)
[20] Lee J.H., Kim S.M., Kim T.Y., Khan U., and Kim S.W., Water droplet-driven triboelectric nanogenerator with superhydrophobic surfaces. Nano Energy. 58: p. 579-584. (2019)
[21] Park D., Won S., Kim K.S., Jung J.Y., Choi J.Y., and Nah J., The influence of substrate-dependent triboelectric charging of graphene on the electric potential generation by the flow of electrolyte droplets. Nano Energy. 54: p. 66-72. (2018)
[22] Tang Q., Wang X., Yang P., and He B., A Solar Cell That Is Triggered by Sun and Rain. Angewandte Chemie - International Edition. 55: p. 5243-5246. (2016)
[23] Yin J., Li X., Yu J., Zhang Z., Zhou J., and Guo W., Generating electricity by moving a droplet of ionic liquid along graphene. Nature Nanotechnology. 9: p. 378-383. (2014)
[24] Zhang Y., Tang Q., He B., and Yang P., Graphene enabled all-weather solar cells for electricity harvest from sun and rain. Journal of Materials Chemistry A. 4: p. 13235-13241. (2016)
[25] Zhao Y., Duan J., He B., and Tang Q., Self-powered flexible monoelectrodes from graphene/reduced graphene oxide composite films to harvest rain energy. Journal of Alloys and Compounds. 776: p. 31-35. (2019)
[26] Zhong H., Xia J., Wang F., Chen H., Wu H., and Lin S., Graphene-Piezoelectric Material Heterostructure for Harvesting Energy from Water Flow. Advanced Functional Materials. 27. (2017)
[27] De N., ’i. h. p. 3: p. 177-222. (1935)
[28] Stangl J., Holý V., and Bauer G., Structural properties of self-organized semiconductor nanostructures. Reviews of Modern Physics. 76: p. 725-783. (2004)
[29] Teo G., Wang H., Wu Y., Guo Z., Zhang J., Ni Z., and Shen Z., Visibility study of graphene multilayer structures. Journal of Applied Physics. 103. (2008)
[30] Juan J.I.N., Graphene%3A Synthesis%2C Functionalization and Applications in Chemistry.pdf. 26. (2010)
[31] Ambrosi A., Chua C.K., Bonanni A., and Pumera M., Electrochemistry of graphene and related materials. Chemical Reviews. 114: p. 7150-7188. (2014)
[32] de Heer W.A., Berger C., Wu X., First P.N., Conrad E.H., Li X., Li T., Sprinkle M., Hass J., Sadowski M.L., Potemski M., and Martinez G., Epitaxial graphene. Solid State Communications. 143: p. 92-100. (2007)
[33] Gao L., Ren W., Zhao J., Ma L.P., Chen Z., and Cheng H.M., Efficient growth of high-quality graphene films on Cu foils by ambient pressure chemical vapor deposition. Applied Physics Letters. 97: p. 95-98. (2010)
[34] Wu W., Yu Q., Peng P., Liu Z., Bao J., and Pei S.S., Control of thickness uniformity and grain size in graphene films for transparent conductive electrodes. Nanotechnology. 23. (2012)
[35] Tuinstra F. and Koenig J.L., Raman Spectrum of Graphite. The Journal of Chemical Physics. 53: p. 1126-1130. (1970)
[36] Malard L.M., Pimenta M.A., Dresselhaus G., and Dresselhaus M.S., Raman spectroscopy in graphene. Physics Reports. 473: p. 51-87. (2009)
[37] Graf D., Molitor F., Ensslin K., Stampfer C., Jungen A., Hierold C., and Wirtz L., Spatially resolved raman spectroscopy of single- and few-layer graphene. Nano Letters. 7: p. 238-242. (2007)
[38] Gupta A., Chen G., Joshi P., Tadigadapa S., and Eklund P.C., Raman scattering from high-frequency phonons in supported n-graphene layer films. Nano Letters. 6: p. 2667-2673. (2006)
[39] Ghosh S., Sood A.K., Ramaswamy S., and Kumar N., Flow-induced voltage and current generation in carbon nanotubes. Physical Review B - Condensed Matter and Materials Physics. 70: p. 1-5. (2004)
[40] Ghosh S., Sood A.K., and Kumar N., -dihydroxylation. 1. 299: p. 1042-1045. (2003)
[41] Liu J., Dai L., and Baur J.W., Multiwalled carbon nanotubes for flow-induced voltage generation. Journal of Applied Physics. 101. (2007)
[42] Král P. and Shapiro M., Nanotube electron drag in flowing liquids. Physical Review Letters. 86: p. 131-134. (2001)
[43] Yin J., Zhang Z., Li X., Zhou J., and Guo W., Harvesting energy from water flow over graphene? Nano Letters. 12: p. 1736-1741. (2012)
[44] Shi G., Liu J., Wang C., Song B., Tu Y., Hu J., and Fang H., Ion enrichment on the hydrophobic carbon-based surface in aqueous salt solutions due to cation-π interactions. Scientific Reports. 3: p. 3-7. (2013)
[45] Li H., Lu T., Pan L., Zhang Y., and Sun Z., Electrosorption behavior of graphene in NaCl solutions. Journal of Materials Chemistry. 19: p. 6773-6779. (2009)
[46] Yin J., Zhang Z., Li X., Yu J., Zhou J., Chen Y., and Guo W., Waving potential in graphene. Nature Communications. 5: p. 1-6. (2014)
[47] He Y., Lao J., Yang T., Li X., Zang X., Li X., Zhu M., Chen Q., Zhong M., and Zhu H., Galvanism of continuous ionic liquid flow over graphene grids. Applied Physics Letters. 107. (2015)
[48] Burgo T.A.L., Galembeck F., and Pollack G.H., Where is water in the triboelectric series? Journal of Electrostatics. 80: p. 30-33. (2016)
[49] Liang Q., Yan X., Gu Y., Zhang K., Liang M., Lu S., Zheng X., and Zhang Y., Highly transparent triboelectric nanogenerator for harvesting water-related energy reinforced by antireflection coating. Scientific Reports. 5: p. 1-7. (2015)
[50] Lin Z.H., Cheng G., Lee S., Pradel K.C., and Wang Z.L., Harvesting water drop energy by a sequential contact-electrification and electrostatic-induction process. Advanced Materials. 26: p. 4690-4696. (2014)
[51] Lin Z.H., Cheng G., Lin L., Lee S., and Wang Z.L., Water-solid surface contact electrification and its use for harvesting liquid-wave energy. Angewandte Chemie - International Edition. 52: p. 12545-12549. (2013)
[52] Dai J.F., Wang G.J., Ma L., and Wu C.K., Surface properties of graphene: Relationship to graphene-polymer composites. Reviews on Advanced Materials Science. 40: p. 60-71. (2015)
[53] Hao Q., Lei W., Xia X., Yan Z., Yang X., Lu L., and Wang X., Exchange of counter anions in electropolymerized polyaniline films. Electrochimica Acta. 55: p. 632-640. (2010)
[54] Stankovich S., Dikin D.A., Dommett G.H.B., Kohlhaas K.M., Zimney E.J., Stach E.A., Piner R.D., Nguyen S.B.T., and Ruoff R.S., Graphene-based composite materials. Nature. 442: p. 282-286. (2006)
[55] Wang Y., Duan J., Zhao Y., He B., and Tang Q., Harvest rain energy by polyaniline-graphene composite films. Renewable Energy. 125: p. 995-1002. (2018)
[56] Koppens F.H.L., Mueller T., Avouris P., Ferrari A.C., Vitiello M.S., and Polini M., Photodetectors based on graphene, other two-dimensional materials and hybrid systems. Nature Nanotechnology. 9(10): p. 780-793. (2014)
[57] Li J., Niu L., Zheng Z., and Yan F., Photosensitive graphene transistors. Advanced Materials. 26: p. 5239-5273. (2014)
[58] Zhang D., Zhou J., Liu C., Guo S., Deng J., Cai Q., Li Z., Zhang Y., Zhang W., and Chen X., Enhanced polarization sensitivity by plasmonic-cavity in graphene phototransistors. Journal of Applied Physics. 126. (2019)
[59] Xue G., Xu Y., Ding T., Li J., Yin J., Fei W., Cao Y., Yu J., Yuan L., Gong L., Chen J., Deng S., Zhou J., and Guo W., Water-evaporation-induced electricity with nanostructured carbon materials. Nature Nanotechnology. 12(4): p. 317-321. (2017)
[60] Ding T., Liu K., Li J., Xue G., Chen Q., Huang L., Hu B., and Zhou J., All-Printed Porous Carbon Film for Electricity Generation from Evaporation-Driven Water Flow. Advanced Functional Materials. 27: p. 1-5. (2017)
[61] Liu K., Ding T., Li J., Chen Q., Xue G., Yang P., Xu M., Wang Z.L., and Zhou J., Thermal–Electric Nanogenerator Based on the Electrokinetic Effect in Porous Carbon Film. Advanced Energy Materials. 8: p. 1-6. (2018)
[62] Li J., Liu K., Xue G., Ding T., Yang P., Chen Q., Shen Y., Li S., Feng G., Shen A., Xu M., and Zhou J., Electricity generation from water droplets via capillary infiltrating. Nano Energy. 48: p. 211-216. (2018)
[63] Tight T.H.-l., Unimpeded Permeation of Water. Science. 335: p. 442-444. (2012)
[64] Li C., Tian Z., Liang L., Yin S., and Shen P.K., Electricity Generation from Capillary-Driven Ionic Solution Flow in a Three-Dimensional Graphene Membrane. ACS Applied Materials & Interfaces. 11: p. 4922-4929. (2019)
[65] Sun Y.Y., Mai V.P., and Yang R.J., Effects of electrode placement position and tilt angles of a platform on voltage induced by NaCl electrolyte flowing over graphene wafer. Applied Energy. 261: p. 114435. (2020)