甲醇在Pt-Fe(111)/C表面吸附的理论研究

Theoretical Study on the Adsorption of Methanol over the Pt-Fe(111)/C Surface

采用密度泛函理论和周期平板模型相结合的方法,对CH3OH分子在Pt-Fe(111)/C表面top,fcc,hcp和bridge位的吸附模型进行了构型优化、能量计算,结果表明bridge位是较有利的吸附位.掺杂后费米能级的位置发生了右移,价带和导带均增宽,极利于电子-空穴的迁移,这对提高催化活性是非常有利的.考察抗中毒性发现:CO在Pt(111)/C面上的吸附能比甲醇吸附能要高,CO在Pt-Fe(111)/C的吸附能比甲醇吸附能要低,可说明CO在Pt(111)/C面上有中毒效应,而Pt-Fe(111)/C的抗CO中毒能力增强,是催化氧化甲醇良好的催化剂.

The density functional theory （DFT） and self-consistent periodic slab calculations were used to investigate the methanol adsorption on Pt-Fe（111）/C surface. The adsorption energy, equilibrium geometry and vibrational frequency of CH3OH at four sites （top, fcc, hcp and bridge） on the Pt-Fe（111）/C surface were predicted and the favorite adsorption site for methanol should be the bridge site. The Fermi level of the cluster model moved to right in catalyst Pt-Fe/C compared with catalyst Pt/C. Both the sites of the valence band and conduction band of the doped system have been broadened, which is favorable for electrons to transfer to cavity. Compared with the adsorption energy of CH3OH on Pt（111）/C surface, the adsorption energy of CO is high, and the Pt（111）/C is favorable to be oxidized to lose the activity. It indicates that the catalyst Pt-Fe（111）/C which is in favor of decomposing methanol is of better anti-poisoning ability than that of Pt（111）/C.