水在HfO2(111)和(110)表面的吸附与解离

运用广义梯度近似密度泛函理论方法(GGA-PW91)结合周期平板模型, 研究水分子在二氧化铪(111)和(110)表面不同吸附位置在不同覆盖度下的吸附行为. 通过比较不同吸附位的吸附能和几何构型参数发现:(111)和(110)表面铪原子(top 位)是活性吸附位. 水分子与表面的吸附能值随覆盖度的变化影响较小. 在(111)和(110)表面, 水分子都倾向以氧端与表面铪原子相互作用. 同时也计算了羟基、氧和氢在表面的吸附, Mulliken 电荷布居, 态密度及部分频率. 结果表明, 在两种表面羟基以氧端与表面铪相互作用, 氧原子与表面铪和氧原子同时成键, 而氢原子直接与表面氧原子相互作用形成羟基. 通过过渡态搜索, 水分子在(111)和(110)表面发生解离, 反应能垒分别为9.7和17.3 kJ·mol^-1, 且放热为59.9和47.6 kJ·mol^-1.

Adsorption and Dissociation of Water on HfO2(111) and (110) Surfaces

First-principles calculations based on density functional theory (DFT) with the generalized gradient approximation (GGA-PW91) have been used to investigate the adsorption and dissociation of H₂O molecules on HfO₂(111) and (110) surfaces at different sites with different coverages. It was found that the surface hafnium atom was the active adsorption position of the (111) and (110) surfaces when compared different adsorption energies and various geometrical parameters. Adsorption energies of water on the HfO₂ (111) and (110) surfaces varied slightly as the coverage increased. It was shown that the most favorable configuration of H₂O on the HfO₂(111) and (110) surfaces corresponded to the coordination of H₂O via its oxygen to a surface hafnium atom. Adsorption geometries, Mulliken population charges, density of states, and frequency calculations for HfO₂-OH, HfO₂-O, and HfO₂-H at both surfaces were also carried out. The results showed that the hydroxyl group interacted with the surface by its oxygen atom to surface hafnium atoms. Isolated oxygen atoms bound to surface hafnium and oxygen atoms, while hydrogen atoms interact only with surface oxygen atoms to form hydroxyl groups. For the dissociation reaction, according to transition searching, H₂O→H (ads)+OH (ads). The energy barriers were endothermic by 9.7 and 17.3 kJ· mol^-1 for the (111) surfaces and exothermic by -59.9 and -47.6 kJ·mol^-1 for the (110) surfaces.