摘要
采用密度泛函理论(DFT)和周期平板模型,研究两种WC(0001)表面的几何结构和表面能,并对Pt原子单层(PtML)在两种WC(0001)表面的高对称性吸附位上的吸附能和分离功进行计算.结果发现,终止于W原子的WC(0001)为最稳定的WC(0001)表面,Pt原子单层以hcp位的方式吸附于W终止的WC(0001)表面是PtML/WC(0001)体系最稳定的几何构型.在此基础上研究了CO分子和H原子分别在PtML/WC(0001)表面和具有相似表面结构的Pt(111)表面的吸附行为.在0.25 ML(monolayer)低覆盖度下,与在Pt(111)表面相比,在PtML/WC(0001)表面上的Pt—C间距明显拉长和CO分子吸附能减少,说明PtML/WC(0001)表面抗CO中毒能力比Pt(111)表面高;态密度分析进一步解释了CO分子与不同表面Pt原子的成键机理.在同一覆盖度下,H原子在PtML/WC(0001)表面的最大吸附能等于甚至略高于在Pt(111)表面的,表明Pt/WC对氢气氧化反应具有良好的催化活性,是一种很有前途的质子交换膜燃料电池(PEMFC)阳极催化剂.
Density functional theory（DFT） calculations and periodic slab models were used to investigate the geometrical structures and surface energies of two different WC（0001） surfaces.The adhesion energies and separation work of Pt monolayer adhesion on the two WC（0001） surfaces at high-symmetry sites were calculated.Results show that the W-terminated WC（0001） is favored and that the W-terminated surface with Pt monolayer adhesion at the hcp site is the most stable PtML/WC（0001） structure.On the basis of the above results,the adsorption behavior of the CO molecule and hydrogen atom on the PtML/WC（0001） surface was compared with those obtained on the Pt（111） surface with a surface structure similar to the PtML/WC（0001） surface.At a low coverage of 0.25 ML（monolayer）,an obvious elongation of the Pt—C distance and a decrease in CO adsorption energy show that the PtML/WC（0001） surface,relative to the Pt（111） surface,exhibits much improved resistance to CO poisoning.The density of states further explains the bonding mechanism of CO and Pt atoms on different surfaces.At the same coverage,the maximum hydrogen adsorption energy on the PtML/WC（0001） surface is equal to or even slightly higher than that on the Pt（111） surface.This suggests that Pt/WC possesses good catalytic activity during the hydrogen oxidation reaction and is a promising alternative anode catalyst for proton exchange membrane fuel cells（PEMFC）.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2010年第1期155-162,共8页
Acta Physico-Chimica Sinica
基金
浙江省国际合作重大科技专项(2008c14040)资助项目~~
