Theoretical Studies For The Mechanisms of H2S Dissociation and Sulfur Oxidation on Pure Metal Ni(111) and Pt(111) and Bimetal Ni@Pt(111) and Pt@Ni(111) Surfaces

• Main Author: 葉丞豪
• Other Authors: 何嘉仁
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/70627754536295319746

碩士 === 國立臺灣師範大學 === 化學系 === 99 === Sulfur, a pollutant well known to poison fuel-cell electrodes, generally comes from S-containing species such as hydrogen sulfide (H2S). The S-containing species becomes adsorbed on the metal electrodes and leaves atomic S strongly bound to the metal surface. The surface sulfur can be removed typically by oxidation with O2 into gaseous SO2. According to our DFT calculations, oxidation of sulfur at 0.25 ML surface sulfur coverage on pure Pt(111) and Ni(111) metal surfaces is exothermic and the reaction barriers of SO2 formation are 0.41 and 1.07 eV, respectively. Various metals in combination to form bimetallic surfaces are reported to tune the catalytic capabilities toward some reactions. Our results show that it is more difficult to remove surface sulfur from a Ni@Pt(111) surface with reaction barrier 1.86 eV for SO2 formation than from a Pt@Ni(111) surface, 0.13 eV. In summary, our calculated order of reactivity for sulfur oxidation reaction is Pt@Ni(111) > Pt(111) > Ni(111) > Ni@Pt(111) at either 0.25 or 0.11 ML coverage of sulfur. In addition, by calculating H¬2S dissociation on Pt@Ni(111), which display poorly reactivity by the endothermic reaction so that Pt@Ni(111) surface can enhance the sulfur tolerance to the metal electrodes.