應用光電化學觸媒法還原二氧化碳產製化學品之研究

Abstract

隨著全球經濟的發展，所耗用之石化資源不斷的增加，也伴隨著汙染物的產生。其中以二氧化碳的排放為世界關注重點，所造成的全球暖化問題為最大議題之一。科學證據顯示人為活動為造成近百年來的全球暖化現象之主因。故CO2減量議題成為目前全球所關注的焦點之一。 本研究主要利用電解還原反應將CO2還原形成可再利用之能源 (如CH4、C2H6及CO) 及化工原料 (如C2H4及HCOOH)。所使用之還原程序有下列三種。(1) 電解還原程序：藉由電解水分子產生H+及電子之傳遞，將CO2選擇性還原生成CH4、C2H6、C2H4、CO及HCOOH；其氣相碳源產率達50%。(2) 光觸媒催化還原程序：利用改質之二氧化鈦光觸媒在不同光源波長下激發產生電子電洞對，可選擇性還原CO2為CH4及C2H4，氣相碳源產率約為10%。(3) 光電化學觸媒還原程序：合併電解還原與光觸媒還原程序使氣相碳原產率提升，可將CO2還原生成CH4、C2H4、C2H6、CO、HCOOH及副產物H2；其氣相碳源產率可達70%。利用此光電化學觸媒還原程序可選擇性還原CO2生成碳氫化合物等石化資源，一方面提供做為工業用原料，另一方面可以降低溫室氣體CO2排放問題，為減碳科技之新穎技術之一。

Along with the prompt development of every country, two special problems are generated all over the world. The first problem is the increasing comsumption of energy and the other one is the deterious pollution of environment. There are many evidences showing that global warming is caused by human activity. Therefore, every country focuses on the emission of CO2 to the atmosphere from power plants, industries and so on. The study investigated the application of reduction of carbon dioxide to useful chemicals via photo-electro-catalytic reduction (PECR) method. The first part of this study directly applied electrolysis reduction process (ER) to generate a certain mount of electron and hydrogen ion for selectively converting gaseous CO2 to hydrocarbons including methane (CH4), ethane (C2H6), ethylene (C2H4), carbon monoxide (CO) and formic acid (HCOOH). The yield of gaseous carbon species (Yc) other than CO2 can reach about 50%. For the second part, different modified catalysts were introduced in the photo-catalytic process (PCR) to reduce the gaseous CO2, giving Yc of about 10%. Finally, the first two reduction processes were combined to concert the CO2. This novel PECR process can convert carbon dioxide more efficiently, resulting in a high Yc of 73%. Thus the application of the proposed PECR process can not only reuse CO2 to reduce the global warming potential, but also produce useful chemicals for industrial usage. For those advantages, the PECR process may be a feasible technology in the future.