隨著全球暖化的影響，地球上的環境也發生了巨大的變化，因此若能將二氧化碳有效轉換成碳氫化合物，必定能為地球減少許多負擔，因此本研究利用人造光合成系統將其轉換，作為新興的替代能源，期望能改善環境和能源議題。
本論文使用的二維材料為過渡金屬二硫族化合物，並選擇二硫化鉬薄膜作為光觸媒材料。使用熱蒸鍍和化學氣相沉積法來合成三奈米二硫化鉬薄膜於不同基板上，如二氧化矽/矽、氧化鋁、二氧化矽、鈦酸鍶基板，並將這些材料作為光觸媒，並藉由應變效應將其應用在探討二氧化碳光催化還原上。
在合成不同厚度二硫化鉬的製程中，我們可以有效的控制二硫化鉬薄膜的厚度，並將其藉由拉曼分析顯示，不同厚度的二硫化鉬薄膜其表面是非常均勻的，且具備良好的可見光吸收波段，並根據實驗結果得知三奈米二硫化鉬薄膜具有最好的光催化效率。並使用不同硫化的製程來將三奈米二硫化鉬薄膜優化，根據拉曼和光激發螢光結果得知，使用硫粉製程的三奈米二硫化鉬薄膜品質是最好的，並根據實驗結果得知其光催化效率比使用硫化氫較高。
綜合以上實驗結果，我們選用硫粉製程的三奈米二硫化鉬薄膜，並成長在四種不同的基板上，而這些基板分別為二氧化矽/矽、氧化鋁、二氧化矽、鈦酸鍶基板，並藉由儀器分析，來測定其厚度、應變效應以及能隙大小，根據實驗結果可以得知，當應變較小時，其光催化效率不好，當應變增加到一定值時，其光催化效率為最高，而當應變太大時，其會增加光催化產物選擇性，而這些反應機制值得未來進一步地加以探討。

Due to global warming, many scientists are studying how to reduce the greenhouse effect. This study used the transition metal dichalcogenides (TMDCs) as the photocatalysts for CO2 photoreduction. Molybdenum disulfide (MoS2) thin-film has been particularly found in unique applications in catalysis, optoelectronics, transistors, etc.
Lattice strain can enhance the activity and selectivity of electrochemical reactions by breaking the linear scaling relationship. Notwithstanding, the explicit use of strain to affect the CO2 reduction reaction (CO2RR) is rarely reported. In this perspective, we highlight the opportunity to use strain to affect the activity and selectivity of CO2RR photocatalysts. We use the thermal evaporation and chemical vapor deposition two-step process to synthesize the uniform molybdenum disulfide (MoS2) thin-film on 4 different kinds of substrates, such as silicon dioxide, sapphire, silica, and STO. By using different kinds of substrate molybdenum disulfide thin-film as photocatalysts, and investigate molybdenum disulfide (MoS2) thin-film strain effect for CO2 photoreduction.
In our process, we can well control the different thicknesses of molybdenum disulfide (MoS2), and it shows good light absorption in the visible light region. Furthermore, the result of GC had shows 3 nm molybdenum disulfide (MoS2) thin-film possess the best photoreduction efficiency than other thickness. Meanwhile, we also do the different kinds of sulfurization processes to better our 3 nm molybdenum disulfide (MoS2) thin-film. The Raman and PL result shows that the sulfur powder process of 3 nm molybdenum disulfide (MoS2) thin-film has better quality than the others. It also shows the highest photoreduction efficiency than the H2S process.
Combining the above results, we use the sulfur process to synthesize 3 nm molybdenum disulfide (MoS2) thin-film, and growing on 4 different kinds of substrates. According to Raman analysis, we can get the E12g and A1g vibration mode, using these two vibration modes to compute the strain and plot the strain-charge doping map (ε-n map). The GC result shows the lowest strain has the lowest photoreduction efficiency when the strain increases to a specific value it shows the highest photoreduction efficiency. If the strain increases too much, it will increase the selectivity of products, and these reaction mechanisms are worthy of further exploration in the future.

[1] Laboratory., N. E. S. R. L. G. M. Trends in Atmospheric Carbon Dioxide. https://gml.noaa.gov/ccgg/trends/.
[2] Gan, P.; Liu, F.; Li, R.; Wang, S.; Luo, J., Chloroplasts- Beyond Energy Capture and Carbon Fixation: Tuning of Photosynthesis in Response to Chilling Stress. Int J Mol Sci 2019, 20 (20).
[3] Wu, J.; Huang, Y.; Ye, W.; Li, Y., CO2 Reduction: From the Electrochemical to Photochemical Approach. Advanced Science 2017, 4 (11), 1700194.
[4] Fu, J.; Jiang, K.; Qiu, X.; Yu, J.; Liu, M., Product selectivity of photocatalytic CO2 reduction reactions. Materials Today 2020, 32, 222-243.
[5] Li, X.; Wen, J.; Low, J.; Fang, Y.; Yu, J., Design and fabrication of semiconductor photocatalyst for photocatalytic reduction of CO2 to solar fuel. Science China Materials 2014, 57 (1), 70-100.
[6] Hong, J.; Zhang, W.; Ren, J.; Xu, R., Photocatalytic reduction of CO2: a brief review on product analysis and systematic methods. Analytical Methods 2013, 5 (5), 1086-1097.
[7] Joe, J.; Yang, H.; Bae, C.; Shin, H., Metal Chalcogenides on Silicon Photocathodes for Efficient Water Splitting: A Mini Overview. Catalysts 2019, 9 (2), 149.
[8] Kraeutler, B.; Bard, A. J., Heterogeneous photocatalytic preparation of supported catalysts. Photodeposition of platinum on titanium dioxide powder and other substrates. Journal of the American Chemical Society 1978, 100 (13), 4317-4318.
[9] Wang, R.; Hashimoto, K.; Fujishima, A.; Chikuni, M.; Kojima, E.; Kitamura, A.; Shimohigoshi, M.; Watanabe, T., Light-induced amphiphilic surfaces. Nature 1997, 388 (6641), 431-432.
[10] Frank, S. N.; Bard, A. J., Heterogeneous photocatalytic oxidation of cyanide ion in aqueous solutions at titanium dioxide powder. Journal of the American Chemical Society 1977, 99 (1), 303-304.
[11] Handoko, A. D.; Tang, J., Controllable proton and CO2 photoreduction over Cu2O with various morphologies. International Journal of Hydrogen Energy 2013, 38 (29), 13017-13022.
[12] Pastor, E.; Pesci, F. M.; Reynal, A.; Handoko, A. D.; Guo, M.; An, X.; Cowan, A. J.; Klug, D. R.; Durrant, J. R.; Tang, J., Interfacial charge separation in Cu2O/RuOx as a visible light driven CO2 reduction catalyst. Physical Chemistry Chemical Physics 2014, 16 (13), 5922-5926.
[13] Yahaya, A. H.; Gondal, M. A.; Hameed, A., Selective laser enhanced photocatalytic conversion of CO2 into methanol. Chemical Physics Letters 2004, 400 (1), 206-212.
[14] Jelinska, A.; Bienkowski, K.; Jadwiszczak, M.; Pisarek, M.; Strawski, M.; Kurzydlowski, D.; Solarska, R.; Augustynski, J., Enhanced Photocatalytic Water Splitting on Very Thin WO3 Films Activated by High-Temperature Annealing. ACS Catalysis 2018, 8 (11), 10573-10580.
[15] Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A., Electric Field Effect in Atomically Thin Carbon Films. Science 2004, 306 (5696), 666.
[16] Geim, A. K.; Novoselov, K. S., The rise of graphene. Nature Materials 2007, 6 (3), 183-191.
[17] Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Katsnelson, M. I.; Grigorieva, I. V.; Dubonos, S. V.; Firsov, A. A., Two-dimensional gas of massless Dirac fermions in graphene. Nature 2005, 438 (7065), 197-200.
[18] Tombros, N.; Jozsa, C.; Popinciuc, M.; Jonkman, H. T.; van Wees, B. J., Electronic spin transport and spin precession in single graphene layers at room temperature. Nature 2007, 448 (7153), 571-574.
[19] Wang, X.; Zhi, L.; Müllen, K., Transparent, Conductive Graphene Electrodes for Dye-Sensitized Solar Cells. Nano Letters 2008, 8 (1), 323-327.
[20] Chhowalla, M.; Shin, H. S.; Eda, G.; Li, L.-J.; Loh, K. P.; Zhang, H., The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. Nature Chemistry 2013, 5 (4), 263-275.
[21] Wang, Q. H.; Kalantar-Zadeh, K.; Kis, A.; Coleman, J. N.; Strano, M. S., Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. Nature Nanotechnology 2012, 7 (11), 699-712.
[22] Splendiani, A.; Sun, L.; Zhang, Y.; Li, T.; Kim, J.; Chim, C.-Y.; Galli, G.; Wang, F., Emerging Photoluminescence in Monolayer MoS2. Nano Letters 2010, 10 (4), 1271-1275.
[23] Novoselov, K.; Castro Neto, A., Two-dimensional crystals-based heterostructures: Materials with tailored properties. Physica Scripta 2012, 2012, 014006.
[24] Radisavljevic, B.; Whitwick, M. B.; Kis, A., Integrated Circuits and Logic Operations Based on Single-Layer MoS2. ACS Nano 2011, 5 (12), 9934-9938.
[25] Radisavljevic, B.; Radenovic, A.; Brivio, J.; Giacometti, V.; Kis, A., Single-layer MoS2 transistors. Nature Nanotechnology 2011, 6 (3), 147-150.
[26] Magda, G. Z.; Pető, J.; Dobrik, G.; Hwang, C.; Biró, L. P.; Tapasztó, L., Exfoliation of large-area transition metal chalcogenide single layers. Scientific Reports 2015, 5 (1), 14714.
[27] Wang, H.; Lu, Z.; Xu, S.; Kong, D.; Cha, J. J.; Zheng, G.; Hsu, P.-C.; Yan, K.; Bradshaw, D.; Prinz, F. B.; Cui, Y., Electrochemical tuning of vertically aligned MoS2 nanofilms and its application in improving hydrogen evolution reaction. Proceedings of the National Academy of Sciences 2013, 110 (49), 19701-19706.
[28] Gong, C.; Zhang, H.; Wang, W.; Colombo, L.; Wallace, R.; Cho, K., Band alignment of two-dimensional transition metal dichalcogenides: Application in tunnel field effect transistors. Applied Physics Letters 2013, 103.
[29] Li, X.; Zhu, H., Two-dimensional MoS2: Properties, preparation, and applications. Journal of Materiomics 2015, 1 (1), 33-44.
[30] Kuc, A.; Zibouche, N.; Heine, T., Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2 Physical Review B 2011, 83 (24), 245213.
[31] Mak, K. F.; Lee, C.; Hone, J.; Shan, J.; Heinz, T. F., Atomically Thin MoS2: A New Direct-Gap Semiconductor. Physical Review Letters 2010, 105 (13), 136805.
[32] Ferrari, A. C.; Meyer, J. C.; Scardaci, V.; Casiraghi, C.; Lazzeri, M.; Mauri, F.; Piscanec, S.; Jiang, D.; Novoselov, K. S.; Roth, S.; Geim, A. K., Raman Spectrum of Graphene and Graphene Layers. Physical Review Letters 2006, 97 (18), 187401.
[33] Tonndorf, P.; Schmidt, R.; Böttger, P.; Zhang, X.; Börner, J.; Liebig, A.; Albrecht, M.; Kloc, C.; Gordan, O.; Zahn, D. R. T.; Michaelis de Vasconcellos, S.; Bratschitsch, R., Photoluminescence emission and Raman response of monolayer MoS2, MoSe2, and WSe2. Opt. Express 2013, 21 (4), 4908-4916.
[34] Lee, C.; Yan, H.; Brus, L. E.; Heinz, T. F.; Hone, J.; Ryu, S., Anomalous Lattice Vibrations of Single- and Few-Layer MoS2. ACS Nano 2010, 4 (5), 2695-2700.
[35] Frey, G. L.; Tenne, R.; Matthews, M. J.; Dresselhaus, M. S.; Dresselhaus, G., Raman and resonance Raman investigation of MoS2 nanoparticles. Physical Review B 1999, 60 (4), 2883-2892.
[36] Molina-Sánchez, A.; Wirtz, L., Phonons in single-layer and few-layer MoS2 and WS2 Physical Review B 2011, 84 (15), 155413.
[37] Conley, H. J.; Wang, B.; Ziegler, J. I.; Haglund, R. F., Jr.; Pantelides, S. T.; Bolotin, K. I., Bandgap engineering of strained monolayer and bilayer MoS2. Nano Lett 2013, 13 (8), 3626-30.
[38] Zhu, H.; Wang, Y.; Xiao, J.; Liu, M.; Xiong, S.; Wong, Z. J.; Ye, Z.; Ye, Y.; Yin, X.; Zhang, X., Observation of piezoelectricity in free-standing monolayer MoS2. Nature Nanotechnology 2015, 10 (2), 151-155.
[39] Ahn, G. H.; Amani, M.; Rasool, H.; Lien, D.-H.; Mastandrea, J. P.; Ager Iii, J. W.; Dubey, M.; Chrzan, D. C.; Minor, A. M.; Javey, A., Strain-engineered growth of two-dimensional materials. Nature Communications 2017, 8 (1), 608.
[40] Chae, W. H.; Cain, J. D.; Hanson, E. D.; Murthy, A. A.; Dravid, V. P., Substrate-induced strain and charge doping in CVD-grown monolayer MoS2. Applied Physics Letters 2017, 111 (14), 143106.
[41] Lee, L.; Tang, S.-Y.; Chen, J.-H.; Su, T.-Y.; Chen, H.-C.; Lin, C.-H.; Chiang, C.-Y.; Chiu, S.-J.; Ku, C.-S.; Shen, J.-L.; Wang, Z. M.; Chueh, Y.-L., Nanoprobing of MoS2 by Synchrotron Radiation When van der Waals Epitaxy Is Locally Invalid. ACS Applied Materials & Interfaces 2020, 12 (28), 32041-32053.
[42] Chang, C.-Y.; Lin, H.-T.; Lai, M.-S.; Yu, C.-L.; Wu, C.-R.; Chou, H.-C.; Lin, S.-Y.; Chen, C.; Shih, M.-H., Large-Area and Strain-Reduced Two-Dimensional Molybdenum Disulfide Monolayer Emitters on a Three-Dimensional Substrate. ACS Applied Materials & Interfaces 2019, 11 (29), 26243-26249.
[43] Jansonius, R. P.; Reid, L. M.; Virca, C. N.; Berlinguette, C. P., Strain Engineering Electrocatalysts for Selective CO2 Reduction. ACS Energy Letters 2019, 4 (4), 980-986.
[44] Khorshidi, A.; Violet, J.; Hashemi, J.; Peterson, A. A., How strain can break the scaling relations of catalysis. Nature Catalysis 2018, 1 (4), 263-268.
[45] Li, H.; Tsai, C.; Koh, A. L.; Cai, L.; Contryman, A. W.; Fragapane, A. H.; Zhao, J.; Han, H. S.; Manoharan, H. C.; Abild-Pedersen, F.; Nørskov, J. K.; Zheng, X., Activating and optimizing MoS2 basal planes for hydrogen evolution through the formation of strained sulphur vacancies. Nat Mater 2016, 15 (1), 48-53.
[46] Nørskov, J. K.; Bligaard, T.; Rossmeisl, J.; Christensen, C. H., Towards the computational design of solid catalysts. Nat Chem 2009, 1 (1), 37-46.
[47] Shi, Y.; Wang, J.; Wang, C.; Zhai, T.-T.; Bao, W.-J.; Xu, J.-J.; Xia, X.-H.; Chen, H.-Y., Hot Electron of Au Nanorods Activates the Electrocatalysis of Hydrogen Evolution on MoS2 Nanosheets. Journal of the American Chemical Society 2015, 137 (23), 7365-7370.
[48] Wang, H.; Tsai, C.; Kong, D.; Chan, K.; Abild-Pedersen, F.; Nørskov, J. K.; Cui, Y., Transition-metal doped edge sites in vertically aligned MoS2 catalysts for enhanced hydrogen evolution. Nano Research 2015, 8 (2), 566-575.
[49] Sun, Y.; Gao, S.; Lei, F.; Xie, Y., Atomically-thin two-dimensional sheets for understanding active sites in catalysis. Chemical Society Reviews 2015, 44 (3), 623-636.
[50] Bollinger, M. V.; Lauritsen, J. V.; Jacobsen, K. W.; Nørskov, J. K.; Helveg, S.; Besenbacher, F., One-Dimensional Metallic Edge States in MoS2 Physical Review Letters 2001, 87 (19), 196803.
[51] Jaramillo, T. F.; Jørgensen, K. P.; Bonde, J.; Nielsen, J. H.; Horch, S.; Chorkendorff, I., Identification of Active Edge Sites for Electrochemical H2 Evolution from MoS2 Nanocatalysts. Science 2007, 317 (5834), 100-102.
[52] Voiry, D.; Shin, H. S.; Loh, K. P.; Chhowalla, M., Low-dimensional catalysts for hydrogen evolution and CO2 reduction. Nature Reviews Chemistry 2018, 2 (1), 0105.
[53] Bashir, A.; Awan, T. I.; Tehseen, A.; Tahir, M. B.; Ijaz, M., Chapter 3 - Interfaces and surfaces. In Chemistry of Nanomaterials, Awan, T. I.; Bashir, A.; Tehseen, A., Eds. Elsevier: 2020; pp 51-87.
[54] Zhang, J. X. J.; Hoshino, K., Chapter 2 - Fundamentals of nano/microfabrication and scale effect. In Molecular Sensors and Nanodevices (Second Edition), Zhang, J. X. J.; Hoshino, K., Eds. Academic Press: 2019; pp 43-111.
[55] Sun, L.; Yuan, G.; Gao, L.; Yang, J.; Chhowalla, M.; Gharahcheshmeh, M. H.; Gleason, K. K.; Choi, Y. S.; Hong, B. H.; Liu, Z., Chemical vapour deposition. Nature Reviews Methods Primers 2021, 1 (1), 5.
[56] Jones, R. R.; Hooper, D. C.; Zhang, L.; Wolverson, D.; Valev, V. K., Raman Techniques: Fundamentals and Frontiers. Nanoscale Research Letters 2019, 14 (1), 231.
[57] 維基百科., 原子力顯微鏡 Atomic Force Microscope. 2020.
[58] Asmatulu, R.; Khan, W. S., Chapter 13 - Characterization of electrospun nanofibers. In Synthesis and Applications of Electrospun Nanofibers, Asmatulu, R.; Khan, W. S., Eds. Elsevier: 2019; pp 257-281.
[59] Laboratories., E., 紫外/可見/近紅外光譜（UV / VIS / NIR）. 2019.
[60] Renishaw., Photoluminescence explained. 2018.
[61] Lin, Y.-K.; Chen, R.-S.; Chou, T.-C.; Lee, Y.-H.; Chen, Y.-F.; Chen, K.-H.; Chen, L.-C., Thickness-Dependent Binding Energy Shift in Few-Layer MoS2 Grown by Chemical Vapor Deposition. ACS Applied Materials & Interfaces 2016, 8 (34), 22637-22646.
[62] Lin, Y.-C.; Zhang, W.; Huang, J.-K.; Liu, K.-K.; Lee, Y.-H.; Liang, C.-T.; Chu, C.-W.; Li, L.-J., Wafer-scale MoS2 thin layers prepared by MoO3 sulfurization. Nanoscale 2012, 4 (20), 6637-6641.
[63] Xu, X.; Wang, Z.; Lopatin, S.; Quevedo-Lopez, M. A.; Alshareef, H. N., Wafer scale quasi single crystalline MoS 2 realized by epitaxial phase conversion. 2D Materials 2018, 6 (1), 015030.
[64] Zhan, Y.; Liu, Z.; Najmaei, S.; Ajayan, P. M.; Lou, J., Large-Area Vapor-Phase Growth and Characterization of MoS2 Atomic Layers on a SiO2 Substrate. Small 2012, 8 (7), 966-971.
[65] Lee, Y.; Lee, J.; Bark, H.; Oh, I.-K.; Ryu, G. H.; Lee, Z.; Kim, H.; Cho, J. H.; Ahn, J.-H.; Lee, C., Synthesis of wafer-scale uniform molybdenum disulfide films with control over the layer number using a gas phase sulfur precursor. Nanoscale 2014, 6 (5), 2821-2826.
[66] Zhang, L.; Lu, Z.; Song, Y.; Zhao, L.; Bhatia, B.; Bagnall, K. R.; Wang, E. N., Thermal Expansion Coefficient of Monolayer Molybdenum Disulfide Using Micro-Raman Spectroscopy. Nano Letters 2019, 19 (7), 4745-4751.
[67] Techniques, L. F. T. S. o. N. P., Silicon Dioxide Properties. 2010.
[68] El-Mahalawy, S. H.; Evans, B. L., The thermal expansion of 2H-MoS2, 2H-MoSe2 and 2H-WSe2 between 20 and 800°C. Journal of Applied Crystallography 1976, 9 (5), 403-406.