甲醛在Ni(110)面上分解的分子轨道研究

本文应用CNDO方法研究了H_2CO在Ni(110)面上的分解反应。证明了金属镍使H_2CO对称禁阻的热分解反应变成了对称允许反应; 讨论了H_2CO在Ni(110)面上的各种吸附模型; 论证了卧式多中心吸附作为H_2CO分解的中间步骤。

CNDO CALCULATIONS FOR DECOMPOSITION OF FORMALDEHYDE ON Ni (110) SURFACE

CNDO calculations for decomposition of formaldehyde on Ni(110) surface are carried out. The adsorption models of formaldehyde on Ni(110) surface have been proposed(Fig.3). The total energies of the various models were minimized by cha- nging the Ni-O distance(Fig.6), the equilibrium distances and the adsorotion ener- gies at the equilibrium distances have been obtained(table 2). The relative sta- bilities of the various models are as follows: fourfold hollow site bridge site lying adsorption top site The point group symmery that is pressrved during the decompoiton has been analysed. According to the concept of conservation of orbital symmetry, the decomposition of formaldehyde is thermally forbidden (Fig.4). the d orbital of Ni makes the thermal reaction symmetry allowed. In this way, we illustrated the catalystic effect of nickel.From the data of binding energies, atomic net charge and Mulliken bond order (table 3), it can be concluded that lying adsorption may be as the intermediate tate which is more favourable for the decompoition of formaldehyde than other adsorption models.