摘要
应用单位键指标%D二次指数势 (UBI QEP)方法对汽车尾气净化反应中氮氧化物的分解进行了理论分析 .结果表明 ,NOx 的分解的可能途径为氮氧化物的直接分解、CO还原助解和氮助解离 .在富氧条件下 ,以CO助解为主 .NO的解离存在N2 O中间态 .Ni与Rh一样 ,也是优秀的还原NOx 催化剂 ,若能有效克服表面氧的共吸附 ,Ni
The Vehicle exhaust gas generally contains nitrogen oxides and the fossil fuel which do greatly harm to air environment. Although the use of catalytic converters for the vehicle gas has resulted in considerable progress in the past twenty years, a theoretical framework for explaining the experimental observations is still lacking. We use the UBI-QEP method to analyze the chemisorption species and calculate the energiti of elementary reactions on six metal single crystal surfaces, Pt(111), Pd(111), Rh(111), Ag(111) Cu(111) and Ni(111). It will help us to realize the reaction mechanism and choose the best suitable catalysts. The sequence of chemisorption heat for NOx is Ni > Rh > Cu > Pd > Pt > Ag. The dissociation of NOx decreases along the series Rh approximate to Ni > Cu > Pd > Pt > Ag. The decomposition of NO can easy happen via N2O intermediate. From calculations at low coverage, we can see two possible pathways of NOx reduction, the direct dissociation and CO-aided dissociation. At high coverage, however, CO-aided dissociation is main pathway. For complete oxidation of carbon monoxide, Pt, Pd, Ag and Cu are fine catalysts, but both Ni and Rh can not promote it. The Ni-Cu-based catalysts may replace the noble metal catalysts (Pt-Pd-Rh).
基金
国家自然科学基金 (2 97730 37
2 99330 40
2 0 0 2 30 0 1)
福建省自然科学基金 (E9910 0 0 1
E0 0 10 0 0 6 )资助项目~~
