以乙醇為中溫型固態氧化物燃料電池之Ni/SmxCe1-xO2-δ (x= 0, 0.1, 0.2) 陽極觸媒製備及其性質研究

Abstract

The purpose of this study is to prepare the Ni/SmxCe1-xO2-δ (Ni/SDC, x= 0, 0.1, 0.2) catalysts for the Intermediate-Temperature Solid Oxide Fuel Cell (IT-SOFC) anodic electrode and investigate the material characteristic and electrochemical performance of these catalyst materials. The SDC supporter mixed with nickel as the catalysts to form the Ni/SDC catalyst electrode. The Citric-EDTA complex method was used to synthesize SDC supporter with different oxygen vacancies concentration. The catalytic capabilities of production hydrogen and carbon deposition of catalyst materials after ethanol steam reforming were investigated. The best catalyst was chose to measure the hydrogen production and carbon deposition after long term test. This study used two processes to synthesize Ni/SDC catalysts. The different processes were used to mix Ni2+ with SDC support precursor: one is mixed the Ni, Sm, Ce precursors during the process (E system) and SDC supporter was first prepared and then Ni2+ precursor coat on SDC supporter (C system). The processes could prepare the same size of Ni/SDC anodic catalysts. Material characteristics, activity test, long term test and carbon deposition of the prepared catalysts were investigated in detail. The structure of Ni/SDC catalyst was distinguished by XRD. There were no second phases observed in the prepared samples. The catalytic reduce temperature was depend on the amount of Ni, but not depend on the specific surface area of samples. The SEM micrographs show that catalysts E system samples exhibited serious sintering phenomenon, but catalysts of C system samples didn’t. For the activity test of the catalysts, water/ethanol mixture (molar = 3:1) was used as source of ethanol steam reforming. The conditions were measured from 400 to 800 oC. The catalysts of C system had the best catalytic performance. The catalytic of C system not only had high hydrogen production about of 96.62 % but also had good stability, however, the catalysts of E system samples were poor. From the result of carbon deposition analysis, it was found that the catalysts of C system samples had inverse relationship between oxygen vacancies concentrations and amount of carbon deposition. The carbon deposition analysis result consists with the result of SEM, TEM, Raman and TPO. The carbon mechanism was also consists with carbon deposition results. The new anodic catalyst material of Ni/Sm0.2Ce0.8O2-δ–C was test in long term at 700 oC for 24 hrs. Even though the hydrogen production decreased about 13.6 % but it still stabile maintained at 83 %. The phenomenon of carbon deposition was observed and measured by SEM, TGA and Raman. There is carbon tube grow on the surface of catalyst, but the hydrogen production yield didn’t change a lot with amount of carbon deposition increased. There is no second phase observed after long-term test at high temperature. In conclusion, the Ni/Sm0.2Ce0.8O2-δ–C (C system) catalyst had the best catalytic performance. This catalyst had high hydrogen production, low byproduct and good ethanol conversion in ethanol steam reforming. The Ni/Sm0.2Ce0.8O2-δ –C (C system) catalyst may be can be used as the new anodic catalyst electrode in IT-SOFC.