H2在Pt（111）表面吸附及电催化的密度泛函理论

摘要

Pt是燃料电池的重要电催化剂,为研究H2在Pt表面的吸附和氧化行为,采用密度泛函理论,通过构造表面层模型方法,对H2分子在金属态和电极Pt(111)表面Top、Bridge和Hollow三种吸附位进行研究。 H2在Pt(111)表面Hollow位吸附能最大,Top位吸附能最小；电极表面吸附能远大于金属态表面吸附能。吸附过程中H—H键被拉长,吸附后H—H键振动频率比自由分子振动频率减少,产生明显红移。电吸附过程中电子由H2分子向电极Pt(111)表面进行了不同程度的转移。计算结果与实验结果十分相近,从理论上解释了H2在电极Pt表面的电吸附和电催化机理。%The Pt metal is a central electrocatalyst of fuel cell. In order to study the behavior of hydrogen on the Pt surfaces, the adsorption and electrocatalytic oxidation of H2 on the top, bridge and hollow sites of Pt(111) surface were investigated by using density functional theory. The investigation revealed that the most favorable adsorption site was the hollow site. The adsorption energy on the electrode surface was more than that on the metallic surface. The bond length of H—H increased. The vibration frequency of H2 adsorbed was smaller than that of free molecular H2 , namely, a red-shift occurs. Results show that this method can theoretically explain the adsorption and electrocatalytic mechanism of H2 on Pt electrode surface.