硫化亞銅修飾二硫化錫形成奈米異質結構來提升光催化二氧化碳還原效率之研究

Abstract

本研究利用人造光合成作用系統將二氧化碳還原轉換成碳氫化合物，作為未來新興的替代性能源，以期改善愈趨被重視的環境及能源議題，本研究以溶劑熱法合成二硫化錫與硫化亞銅，由於兩種材料的能隙大小與位置能讓二氧化碳還原反應發生，並以異質接面方式混合兩種半導體材料，有效的將激發後所產生的電子與電洞分離，並降低電子電洞輻射復合的現象，使其有較多的激子能夠飄移至材料表面進行二氧化碳還原反應；在本研究中，首先就材料的晶體結構、成份比例及元素、光學性質等特性分析，再利用氣相層析，發現二硫化錫與硫化亞銅分別能產出乙醛及甲醇，兩者材料在二氧化碳還原上具有不同之特性，經由混合兩材料形成異質結構，發現能產出乙醛與大量的乙醇，並有效地提高光化學量子轉換效率，可達到約0.048%，且乙醇是能作為燃料的碳氫化合物，最後藉由改變兩種材料的混合比例來優化反應效率，在不同比例下，本研究發現以0.5:1的比例混合硫化亞銅與二硫化錫，相較於其他比例，光化學量子轉換效率能提高至0.072%，從此研究，能證明利用p-n異質接面結構方法，能有效提高光觸媒在二氧化碳還原反應上的效率。Formation of hydrocarbon from carbon dioxide via artificial photosynthesis is a new and developing alternative energy for solving the environmental energy issue which has gradually been emphasized seriously. We prepare the SnS2 and Cu2S by solvothermal method. The band gap and position of these two materials are suitable for photocatalytic CO2 reduction. We hybrid these two materials to be the heterojunction structure. By this modification, it can effectively separate the electron-hole pairs and suppress the charge recombination. There are more carriers which can diffuse to the surface and involve in CO2 reduction. At first, we analyze the crystal structure, composition and element, optical property. Then we detect the photocatalytic efficiency by gas chromatography. The SnS2 and Cu2S can produce the acetaldehyde and methanol respectively. They have different selectivity on CO2 reduction. After hybridization of these two materials and forming the heterostructure, it can produce the acetaldehyde and a lot of ethanol. The quantum efficiency is effectively increased and up to 0.058%. The ethanol is a well hydrocarbon as the fuel. At the last, we try to optimize the system by tuning the ratio of these two materials. When the ratio of these two material is 0.5:1, it has the highest quantum efficiency and up to 0.072%. By this study, the p-n junction structure can effectively enhance the photocatalytic CO2 reduction.