由於全球快速發展與社會變遷，在能量的產生與儲存應用上之需求快速增加，傳統的化石燃料因其在環境污染與存量及其開發過程所存在的隱憂，使其替代方案諸如太陽能電池、燃料電池、超級電容等能量的生產與儲存的方案備受矚目。
自石墨烯材料的合成與應用機制被提出以來，碳基材料在各領域的應用都引起相當多的研究興趣，其中因為石墨烯具有高比表面積與導電、導熱等特性，在電化學領域，尤其儲能材料之應用層面在近年引起相當大的關注，在這個領域有兩個主要方向，其一是以高能量密度為主的電池，二則是高功率密度的電容器，提升電池的功率密度或電容的能量密度是對此類材料應用研究的重心。本研究中使用銅作為電容材料，經由水熱反應製備銅氧化物，將之與石墨烯複合形成複合材料，研究中探討水熱反應過程的酸鹼度與反應時間對樣品的表面形貌之影響，並研究不同參數製備的電容材料所表現的電化學特性。
實驗結果顯示氧化石墨烯在pH 12的水熱環境製備之還原氧化石墨烯（reduced graphene oxide，RGO）具有最高的電容表現能力。研究水熱過程酸鹼度對銅氧化物表面形貌的影響結果，可以發現提升環境偏向強鹼可以生成尺寸更小的銅氧化物，提供更多的表面積而給出更高的電容表現。銅氧化物複合還原氧化石墨烯的樣品中則可以觀察到樣品經過複合後能提供更多的電容表現，並且水熱時間的增長對樣品的電化學性能有正向增益。

Due to the rapid global development and social changes, energy storage devices have attracted tremendous attention and were expected to play important roles such as supercapacitors and lithium-ion batteries. Compare to batteries, supercapacitors have higher power density and charging/discharging period. However, the energy density of supercapacitors still lower than the behavior of batteries. In this regard, increasing the energy density of supercapacitors is the main theme of current research. The metal oxide is expected to play roles in enhancing the capacity but suffers from low conductivity. Graphene materials have been considered to have the potential to solve this problem. In addition, graphene-based composites materials are expected to have more stability, which leads to higher cycling retention.
In this study, Cu2O has been chosen as an electrode material and obtain Cu2O/RGO composite through the one-step hydrothermal process. By adjusting the base concentration, reduced graphene oxide (RGO) and Cu2O/RGO composites were synthesized and subjected to electrochemical examinations. Raman spectroscopy and X-ray diffraction spectra were applied to confirm the formation of RGO. In addition, the ID/IG ratio was determined to verify the reduced degree of RGO. The RGO prepared at pH 12 showed the highest degree of reduction. X-ray photoelectron spectra revealed that the characterization peaks of the oxygen-containing functional groups decreased significantly in RGO samples prepared with the hydrothermal process at more basic conditions. After combined RGO and Cu2O, the XRD host lattice was confirmed to the cuprous oxide and led to higher ID/IG ratio in Raman spectra because of more disorder structure. Cyclic voltammetry measurements were carried out to examine the capacity of synthesized composite. It was found that electrodes made of the hybrid composite exhibited much higher capacitance than those of RGO prepared via 8 hours of hydrothermal process at pH 12. With the optimal synthesis parameters, Cu2O/RGO hybrid composites showed the best electrochemical behavior for energy storage with a capacitance of 1036 F/g.

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