太陽能被視為是一種豐饒及可再生的能源，透過適當的能源轉換，將太陽能轉換成人們生活所需的能源，並有效地利用之，已然成為現今發展的重大趨勢。而光熱轉換效應的應用可於生醫上作為熱治療用途及水蒸氣的生成等，近期則逐漸被應用於儲能裝置上，探討其對於裝置性能的提升。本研究中以簡易且一步合成的方式，複合硫化銅(CuS)及石墨烯泡綿(GF)兩種同時具有光熱轉換特性及電化學活性的材料，並於後續施以水熱法之熱處理，加上添加PEDOT:PSS作為助導電物質及贋電容材料使電極效能進一步提升，令其可直接以泡棉的形式應用於固態超級電容器之電極，並在一倍模擬太陽光照射的搭配，使裝置在光熱效應的作用下增強效能。CuS@GF-H/PEDOT電極在充放電電流密度為4.44 mA cm-2時，可擁有1297.14 mF cm-2之面積比電容表現，且於一倍太陽光照射下可使CuS@GF-H/PEDOT電極內部溫度上升至46.2℃，顯示其同時具有良好之電化學表現以及光熱轉換特性。使用聚乙烯醇/氫氧化鉀(PVA/KOH)作為膠態電解質，與CuS@GF-H/PEDOT電極作為超級電容器兩極，組成固態對稱式超級電容器。在充放電電流密度為1mA cm-2時，具有193.33 mF cm-2之面積比電容表現。當於一倍太陽光下測試，面積比電容值可提升至386.62 mF cm-2，是為未照光之約2倍之多，甚至在其他測試條件可達2.5倍。而在能量密度及功率密度方面，可依據Ragone圖得知，在一倍太陽光的照射下，圖形整體會往右上偏移，表示能量密度及功率密度皆因光熱效應而使性能增強。於循環測試中，在充放電循環3000圈後，仍可擁有79.4% 之電容保存率以及在持續照光下循環1200圈，同樣可維持在約77.8%的效能，展現其良好的穩定性。本篇研究除了提供了複合石墨烯泡綿簡易且快速的製備方法，並將複合泡綿直接作為超級電容器之電極，令其在應用端的使用更為真實，亦證明在光熱效應的參與下得使電化學儲能裝置效能獲得提升，展現光熱增強電化學儲能裝置性能足具未來的發展潛力。

Solar energy is seen as an abundant and renewable energy. Through proper energy conversion, converting solar energy into energy needed by people and effectively using it has become a major development trend nowadays. The application of solar-thermal effect can be used as thermal therapy and steam collection. Recently, it has been gradually applied on energy storage devices to explore the improvement of device performance. In this study, a simple and one-step synthesis method is used to combine copper sulfide (CuS) and graphene foam (GF) together, which two materials both have photothermal conversion characteristics and electrochemical activity. After combination of substances, giving it with heat treatment, then adding PEDOT:PSS as a conductive agent and pseudo-capacitive material to promote electrode performance. So that, composite graphene foam could be directly applied as electrodes for solid-state supercapacitor and the device performance could be enhanced by the effect of solar thermal conversion. During the test of three electrode system, CuS@GF-H/PEDOT electrode had an areal capacitance of 1297.14 mF cm-2 when the current density is about 4.44 mA cm-2. In addition, as the electrode is exposed under 1 solar illumination, its internal temperature could be raised to 46.2℃, showing that it not only has good electrochemical performance but has well photothermal conversion effect. In practical uses, a symmetric device is assembled based on two CuS@GF-H/PEDOT electrodes as positive and negative electrode and PVA/KOH as gel electrolyte. When the current density is 1mA cm-2, it has an areal capacitance of 193.33 mF cm-2. If tested under 1 solar illumination, the areal capacitance can be increased to 386.62 mF cm-2, which is about 2 times compared with original one, and even 2.5 times under other testing conditions. In terms of energy density and power density, it can be known from the Ragone plot that under 1 solar illumination, the overall pattern will shift to the upper right, indicating that the energy density and power density are both enhanced by the photothermal effect. In the cycle test, after 3000 cycles, the capacitance retention of device remains at 79.4% and if testing under continuous illumination, its retention maintains at about 77.8% after 1200 cycles, showing its good stability. To sum up, this work provides a simple and fast preparation method for composite graphene foam. Not only that, different from some work, we use composite graphene foam as the electrode of supercapacitor directly, making its use more realistic. Furthermore, it also proves that the participation of photothermal effect in electrochemical energy storage devices could lead better performance. Showing that the photothermal enhancement on electrochemical energy storage devices has potential development in the future.

[1] Wang, G., Zhang, L. & Zhang, J.; A review of electrode materials for electrochemical supercapacitors. Chemical Society Reviews, 41(2), 797-828, 2012.
[2] Pan, Z., Liu, M., Yang, J., Qiu, Y., Li, W., Xu, Y. & Zhang, Y.; High electroactive material loading on a carbon nanotube@ 3D graphene aerogel for high‐performance flexible all‐solid‐state asymmetric supercapacitors. Advanced Functional Materials, 27(27), 1701122, 2017.
[3] Yang, J., Ji, X., Liu, L., Xiang, Y. & Zhu, Y.; One step fabrication of graphene/polypyrrole/Ag composite electrode towards compressible supercapacitor. Journal of Alloys and Compounds, 820, 153081, 2020.
[4] Pedico, A., Lamberti, A., Gigot, A., Fontana, M., Bella, F., Rivolo, P. & Pirri, C. F.; High-performing and stable wearable supercapacitor exploiting rGO aerogel decorated with copper and molybdenum sulfides on carbon fibers. ACS Applied Energy Materials, 1(9), 4440-4447, 2018.
[5] Yi, F., Ren, H., Dai, K., Wang, X., Han, Y., Wang, K.&Liu, Z.; Solar thermal-driven capacitance enhancement of supercapacitors. Energy & Environmental Science, 11(8), 2016-2024, 2018.
[6] Zhao, M., Li, Y., Lin, F., Xu, Y., Chen, L., Jiang, W. & Wang, Y.; A quasi-solid-state photothermal supercapacitor via enhanced solar energy harvest. Journal of Materials Chemistry A, 8(4), 1829-1836, 2020.
[7] Su, Y., Wu, C., Song, Y., Li, Y., Guo, Y. & Xu, S.; Sulfides/3D reduced graphene oxide composite with a large specific surface area for high-performance all-solid-state pseudocapacitors. Applied Surface Science, 488, 134-141 ,2019.
[8] Kim, D. W., Jung, S. M. & Jung, H. Y.; A super-thermostable, flexible supercapacitor for ultralight and high performance devices. Journal of Materials Chemistry A, 8(2), 532-542, 2020.
[9] Zhai, S., Fan, Z., Jin, K., Zhou, M., Zhao, H., Zhao, Y. & Cai, Z.; Synthesis of zinc sulfide/copper sulfide/porous carbonized cotton nanocomposites for flexible supercapacitor and recyclable photocatalysis with high performance. Journal of Colloid and Interface Science, 575, 306-316, 2020.
[10] Goel, S., Chen, F. & Cai, W.; Synthesis and biomedical applications of copper sulfide nanoparticles: from sensors to theranostics. Small, 10(4), 631-645, 2014.
[11] Simon, P. & Gogotsi, Y.; Materials for electrochemical capacitors. Nanoscience and Technology: A Collection of Reviews from Nature Journals, 320-329, 2010.
[12] Muzaffar, A., Ahamed, M. B., Deshmukh, K. & Thirumalai, J.; A review on recent advances in hybrid supercapacitors: Design, fabrication and applications. Renewable and Sustainable Energy Reviews, 101, 123-145, 2019.
[13] Pandolfo, A. G. & Hollenkamp, A. F.; Carbon properties and their role in supercapacitors. Journal of Power Sources, 157(1), 11-27, 2006.
[14] Kongsawatvoragul, K., Kalasina, S., Kidkhunthod, P. & Sawangphruk, M.; Charge storage mechanisms of cobalt hydroxide thin film in ionic liquid and koh electrolytes for asymmetric supercapacitors with graphene aerogel. Electrochimica Acta, 324, 134854 ,2019.
[15] Yang, J., Yu, X., Sun, X., Kang, Q., Zhu, L., Qin, G. & Chen, Q.; Polyaniline-decorated supramolecular hydrogel with tough, fatigue-resistant, and self-healable performances for all-in-one flexible supercapacitors. ACS Applied Materials & Interfaces, 12(8), 9736-9745, 2020.
[16] Salari, H.; Efficient photocatalytic degradation of environmental pollutant with enhanced photocarrier separation in novel Z-scheme a-MnO2 nanorod/a-MoO3 nanocomposites. Journal of Photochemistry and Photobiology A: Chemistry, 401, 112787, 2020.
[17] Chen, W., Wang, X., Zhao, B., Zhang, R., Xie, Z., He, Y., & Yuan, M.; CuS–MnS2 nano-flowers for magnetic resonance imaging guided photothermal/photodynamic therapy of ovarian cancer through necroptosis. Nanoscale, 11(27), 12983-12989, 2019
[18] Zhao, T., Peng, X., Zhao, X., Hu, J., Jiang, T., Lu, X. & Ahmad, I.; Preparation and performance of carbon dot decorated copper sulphide/carbon nanotubes hybrid composite as supercapacitor electrode materials. Journal of Alloys and Compounds, 817, 153057, 2020
[19] Singhal, R., Thorne, D., LeMaire, P. K., Martinez, X., Zhao, C., Gupta, R. K., & Sharma, R. K.; Synthesis and characterization of CuS, CuS/graphene oxide nanocomposite for supercapacitor applications. AIP Advances, 10(3), 035307, 2020.
[20] Tian, Z., Dou, H., Zhang, B., Fan, W., & Wang, X.; Three-dimensional graphene combined with hierarchical CuS for the design of flexible solid-state supercapacitors. Electrochimica Acta, 237, 109-118, 2017.
[21] Xing, W., Qiao, S., Wu, X., Gao, X., Zhou, J., Zhuo, S. & Hulicova-Jurcakova,D.; Exaggerated capacitance using electrochemically active nickel foam as current collector in electrochemical measurement. Journal of Power Sources, 196(8), 4123-4127, 2011.
[22] Jin, K., Zhou, M., Zhao, H., Zhai, S., Ge, F., Zhao, Y., & Cai, Z.; Electrodeposited CuS nanosheets on carbonized cotton fabric as flexible supercapacitor electrode for high energy storage. Electrochimica Acta, 295, 668-676, 2019.
[23] Zhong, C., Deng, Y., Hu, W., Qiao, J., Zhang, L. & Zhang, J.; A review of electrolyte materials and compositions for electrochemical supercapacitors. Chemical Society Reviews, 44(21), 7484-7539, 2015.
[24] Han, X., Xiao, G., Wang, Y., Chen, X., Duan, G., Wu, Y. & Wang, H. Design and fabrication of conductive polymer hydrogels and their applications in flexible supercapacitors. Journal of Materials Chemistry A, 8(44), 23059-23095, 2020.
[25] Jiang, S., Liu, S., & Feng, W.; PVA hydrogel properties for biomedical application. Journal of The Mechanical Behavior of Biomedical Materials, 4(7), 1228-1233, 2011.
[26] Santos, F., Tafur, J. P., Abad, J. & Romero, A. J. F.; Structural modifications and ionic transport of PVA-KOH hydrogels applied in Zn/Air batteries. Journal of Electroanalytical Chemistry, 850, 113380, 2019.
[27] Kumar, C. V. & Pattammattel, A.; Introduction to Graphene: Chemical and Biochemical Applications. Elsevier, 2017.
[28] Van Bommel, A. J., Crombeen, J. E. & Van Tooren, A.; LEED and Auger electron observations of the SiC (0001) surface. Surface Science, 48(2), 463-472, 1975.
[29] Moon, I. K., Ki, B. & Oh, J.; Three-dimensional porous stretchable supercapacitor with wavy structured PEDOT: PSS/graphene electrode. Chemical Engineering Journal, 392, 123794, 2020.
[30] Wang, J., Shi, L., Li, Y., Jin, L., Xu, Y., Zhang, H. & Ma, X.; Thermal management of graphene-induced high-power semiconductor laser package with bidirectional conduction structure. Optics & Laser Technology, 139, 106927, 2021.
[31] Zhang, X., Sui, Z., Xu, B., Yue, S., Luo, Y., Zhan, W. & Liu, B.; Mechanically strong and highly conductive graphene aerogel and its use as electrodes for electrochemical power sources. Journal of Materials Chemistry, 21(18), 6494-6497, 2011.
[32] Xu, Y., Sheng, K., Li, C. & Shi, G.; Self-assembled graphene hydrogel via a one-step hydrothermal process. ACS Nano, 4(7), 4324-4330, 2010.
[33] Pottathara, Y. B., Tiyyagura, H. R., Ahmad, Z. & Sadasivuni, K. K;. Graphene based aerogels: fundamentals and applications as supercapacitors. Journal of Energy Storage, 30, 101549, 2020.
[34] Song, C., Yin, X., Han, M., Li, X., Hou, Z., Zhang, L. & Cheng, L.; Three-dimensional reduced graphene oxide foam modified with ZnO nanowires for enhanced microwave absorption properties. Carbon, 116, 50-58, 2017.
[35] Li, J., Yun, X., Hu, Z., Xi, L., Li, N., Tang, H. & Zhu, Y. Three-dimensional nitrogen and phosphorus co-doped carbon quantum dots/reduced graphene oxide composite aerogels with a hierarchical porous structure as superior electrode materials for supercapacitors. Journal of Materials Chemistry A, 7(46), 26311-26325, 2019.
[36] He, Y., Liu, Y., Wu, T., Ma, J., Wang, X., Gong, Q. & Gao, J.; An environmentally friendly method for the fabrication of reduced graphene oxide foam with a super oil absorption capacity. Journal of Hazardous Materials, 260, 796-805, 2013.
[37] Jung, S. M., Jung, H. Y., Dresselhaus, M. S., Jung, Y. J. & Kong, J.; A facile route for 3D aerogels from nanostructured 1D and 2D materials. Scientific Reports, 2(1), 1-6, 2012.
[38] Li, J., Yu, Y., Chen, D., Liu, G., Li, D., Lee, H. S. & Feng, Y.; Hydrophilic graphene aerogel anodes enhance the performance of microbial electrochemical systems. Bioresource Technology, 304, 122907, 2020.
[39] Tang, Z., Shen, S., Zhuang, J. & Wang, X.; Noble‐metal‐promoted three‐dimensional macroassembly of single‐layered graphene oxide. Angewandte Chemie, 122(27), 4707-4711, 2010.
[40] Zhou, Y., Hu, X., Guo, S., Yu, C., Zhong, S. & Liu, X.; Multi-functional graphene/carbon nanotube aerogels for its applications in supercapacitor and direct methanol fuel cell. Electrochimica Acta, 264, 12-19, 2018.
[41] Tian, W., Cheng, D., Wang, S., Xiong, C. & Yang, Q.; Phytic acid modified manganese dioxide/graphene composite aerogel as high-performance electrode materials for supercapacitors. Applied Surface Science, 495, 143589, 2019.
[42] Korkmaz, S. & Kariper, İ. A.; Graphene and graphene oxide based aerogels: Synthesis, characteristics and supercapacitor applications. Journal of Energy Storage, 27, 101038, 2020.
[43] Wu, H. Y., Li, S. T., Shao, Y. W., Jin, X. Z., Qi, X. D., Yang, J. H. & Wang, Y.; Melamine foam/reduced graphene oxide supported form-stable phase change materials with simultaneous shape memory property and light-to-thermal energy storage capability. Chemical Engineering Journal, 379, 122373, 2020.
[44] Xu, X., Guan, C., Xu, L., Tan, Y. H., Zhang, D., Wang, Y. & Ding, J.; Three dimensionally free-formable graphene foam with designed structures for energy and environmental applications. ACS Nano, 14(1), 937-947, 2019.
[45] Ruiz-Gómez, S., Boscá, A., Pérez, L., Pedros, J., Martinez, J., Páez, A. & Calle, F.; Graphene foam functionalized with electrodeposited nickel hydroxide for energy applications. Diamond and Related Materials, 57, 63-67, 2015.
[46] Wang, C., Chen, X., Wang, B., Huang, M., Wang, B., Jiang, Y. & Ruoff, R. S.; Freeze-casting produces a graphene oxide aerogel with a radial and centrosymmetric structure. ACS Nano, 12(6), 5816-5825, 2018.
[47] Wei, J., Wei, G., Wang, Z., Li, W., Wu, D. & Wang, Q.; Enhanced Solar‐Driven‐Heating and Tough Hydrogel Electrolyte by Photothermal Effect and Hofmeister Effect. Small, 16(44), 2004091, 2020.
[48] He, K., Yao, Z., Hwang, S., Li, N., Sun, K., Gan, H. & Su, D.; Kinetically-driven phase transformation during lithiation in copper sulfide nanoflakes. Nano Letters, 17(9), 5726-5733, 2017.
[49] Zhao, L., Liu, Y., Chang, R., Xing, R. & Yan, X.; Supramolecular photothermal nanomaterials as an emerging paradigm toward precision cancer therapy. Advanced Functional Materials, 29(4), 1806877, 2019.
[50] Vischio, F., Fanizza, E., De Bellis, V., Sibillano, T., Ingrosso, C., Giannini, C. & Depalo, N.; Near-Infrared absorbing solid lipid nanoparticles encapsulating plasmonic copper sulfide nanocrystals. The Journal of Physical Chemistry C, 123(37), 23205-23213, 2019.
[51] Han, B., Zhang, Y. L., Chen, Q. D. & Sun, H. B.; Carbon‐based photothermal actuators. Advanced Functional Materials, 28(40), 1802235, 2018.
[52] Mousavi, S. M., Low, F. W., Hashemi, S. A., Samsudin, N. A., Shakeri, M., Yusoff, Y. & Amin, N.; Development of hydrophobic reduced graphene oxide as a new efficient approach for photochemotherapy. RSC Advances, 10(22), 12851-12863, 2020.
[53] Kelly, K. L., Coronado, E., Zhao, L. L. & Schatz, G. C.; The optical properties of metal nanoparticles: the influence of size, shape, and dielectric environment. The Journal of Physical Chemistry B, 107(3), 668-677, 2003.
[54] Xu, S., Bai, X. & Wang, L.; Exploration of photothermal sensors based on photothermally responsive materials: a brief review. Inorganic Chemistry Frontiers, 5(4), 751-759, 2018.
[55] Robby, A. I., Kim, S. G., Lee, U. H., In, I., Lee, G. & Park, S. Y.; Wireless electrochemical and luminescent detection of bacteria based on surface-coated CsWO3-immobilized fluorescent carbon dots with photothermal ablation of bacteria. Chemical Engineering Journal, 403, 126351, 2021.
[56] Goel, S., Chen, F. & Cai, W.; Synthesis and biomedical applications of copper sulfide nanoparticles: from sensors to theranostics. Small, 10(4), 631-645, 2014.
[57] Raccichini, R., Amores, M. & Hinds, G.; Critical review of the use of reference electrodes in Li-ion batteries: a diagnostic perspective. Batteries, 5(1), 12, 2019.
[58] Kim, B. K., Sy, S., Yu, A., & Zhang, J.; Electrochemical supercapacitors for energy storage and conversion. Handbook of Clean Energy Systems, 1-25, 2015.
[59] Kissinger, P. T. & Heineman, W. R.; Cyclic voltammetry. Journal of Chemical Education, 60(9), 702, 1983.
[60] Xie, J., Yang, P., Wang, Y., Qi, T., Lei, Y. & Li, C. M.; Puzzles and confusions in supercapacitor and battery: Theory and solutions. Journal of Power Sources, 401, 213-223, 2018.
[61] Bard, A. J. & Faulkner, L. R.; Fundamentals and applications. Electrochemical Methods, 2(482), 580-632, 2001.
[62] Rubinson, J. F., & Kayinamura, Y. P.; Charge transport in conducting polymers: insights from impedance spectroscopy. Chemical Society Reviews, 38(12), 3339-3347, 2009.
[63] Nguyen, T. Q. & Breitkopf, C.; Determination of diffusion coefficients using impedance spectroscopy data. Journal of The Electrochemical Society, 165(14), E826, 2018.
[64] Li, J., Zhao, S., Zhang, G., Gao, Y., Deng, L., Sun, R. & Wong, C. P.; A facile method to prepare highly compressible three-dimensional graphene-only sponge. Journal of Materials Chemistry A, 3(30), 15482-15488, 2015.
[65] De, B., Kuila, T., Kim, N. H. & Lee, J. H.: Carbon dot stabilized copper sulphide nanoparticles decorated graphene oxide hydrogel for high performance asymmetric supercapacitor. Carbon, 122, 247-257, 2017.
[66] Zou, X., Zhang, J., Zhao, X. & Zhang, Z.; MoS2/RGO composites for photocatalytic degradation of ranitidine and elimination of NDMA formation potential under visible light. Chemical Engineering Journal, 383, 123084, 2020.
[67] Ping, J. & Johnson, A. C.; Quantifying the intrinsic surface charge density and charge-transfer resistance of the graphene-solution interface through bias-free low-level charge measurement. Applied Physics Letters, 109(1), 013103, 2016
[68] Cossar, E., Houache, M. S., Zhang, Z. & Baranova, E. A.; Comparison of electrochemical active surface area methods for various nickel nanostructures. Journal of Electroanalytical Chemistry, 870, 114246, 2020
[69] Peng, H., Ma, G., Mu, J., Sun, K. & Lei, Z.; Controllable synthesis of CuS with hierarchical structures via a surfactant-free method for high-performance supercapacitors. Materials Letters, 122, 25-28, 2014.
[70] Tian, Z., Wang, X., Li, B., Li, H. & Wu, Y.; High rate capability electrode constructed by anchoring CuCo2S4 on graphene aerogel skeleton toward quasi-solid-state supercapacitor. Electrochimica Acta, 298, 321-329, 2019.
[71] Ardizzone, S., Fregonara, G. & Trasatti, S.; “Inner” and “outer” active surface of RuO2 electrodes. Electrochimica Acta, 35(1), 263-267, 1990.