González Danilo, Heras-Domingo Javier, Pantaleone Stefano, Rimola Albert, Rodríguez-Santiago Luis, Solans-Monfort Xavier, Sodupe Mariona
Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
ACS Omega. 2019 Feb 11;4(2):2989-2999. doi: 10.1021/acsomega.8b03350. eCollection 2019 Feb 28.
Understanding metal oxide MO (M = Ti, Ru, and Ir)-water interfaces is essential to assess the catalytic behavior of these materials. The present study analyzes the HO-MO interactions at the most abundant (110) and (011) surfaces, at two different water coverages: isolated water molecules and full monolayer, by means of Perdew-Burke-Ernzerhof-D2 static calculations and ab initio molecular dynamics (AIMD) simulations. Results indicate that adsorption preferably occurs in its molecular form on (110)-TiO and in its dissociative form on (110)-RuO and (110)-IrO. The opposite trend is observed at the (011) facet. This different behavior is related to the kind of octahedral distortion observed in the bulk of these materials (tetragonal elongation for TiO and tetragonal compression for RuO and IrO) and to the different nature of the vacant sites created, axial on (110) and equatorial on (011). For the monolayer, additional effects such as cooperative H-bond interactions and cooperative adsorption come into play in determining the degree of deprotonation. For TiO, AIMD indicates that the water monolayer is fully undissociated at both (110) and (011) surfaces, whereas for RuO, water monolayer exhibits a 50% dissociation, the formation of HO motifs being essential. Finally, on (110)-IrO, the main monolayer configuration is the fully dissociated one, whereas on (011)-IrO, it exhibits a degree of dissociation that ranges between 50 and 75%. Overall, the present study shows that the degree of water dissociation results from a delicate balance between the HO-MO intrinsic interaction and cooperative hydrogen bonding and adsorption effects.
了解金属氧化物MO（M = Ti、Ru和Ir）-水界面对于评估这些材料的催化行为至关重要。本研究通过Perdew-Burke-Ernzerhof-D2静态计算和从头算分子动力学（AIMD）模拟，分析了在两种不同水覆盖率下，即孤立水分子和完整单层水，在最丰富的（110）和（011）表面上的HO-MO相互作用。结果表明，吸附在（110）-TiO上优选以分子形式发生，而在（110）-RuO和（110）-IrO上以解离形式发生。在（011）晶面观察到相反的趋势。这种不同的行为与这些材料本体中观察到的八面体畸变类型（TiO为四方伸长，RuO和IrO为四方压缩）以及产生的空位的不同性质有关，（110）面上为空位轴向，（011）面上为空位赤道向。对于单层水，诸如协同氢键相互作用和协同吸附等额外效应在确定去质子化程度时发挥作用。对于TiO，AIMD表明水单层在（110）和（011）表面均完全未解离，而对于RuO，水单层表现出50%的解离，HO基序的形成至关重要。最后，在（110）-IrO上，主要的单层构型是完全解离的，而在（011）-IrO上，其解离程度在50%至75%之间。总体而言，本研究表明水的解离程度源于HO-MO固有相互作用与协同氢键和吸附效应之间的微妙平衡。
