Department of Chemistry, The University of Reading, Whiteknights, Reading RG6 6AD, United Kingdom.
J Chem Phys. 2009 Dec 7;131(21):214707. doi: 10.1063/1.3266941.
The adsorption of water and coadsorption with oxygen on Rh{111} under ultrahigh vacuum conditions was studied using synchrotron-based photoemission and photoabsorption spectroscopy. Water adsorbs intact on the clean surface at temperatures below 154 K. Irradiation with x-rays, however, induces fast dissociation and the formation of a mixed OH+H(2)O layer indicating that the partially dissociated layer is thermodynamically more stable. Coadsorption of water and oxygen at a coverage below 0.3 monolayers has a similar effect, leading to the formation of a hydrogen-bonded network of water and hydroxyl molecules at a ratio of 3:2. The partially dissociated layers are more stable than chemisorbed intact water with the maximum desorption temperatures up to 30 K higher. For higher oxygen coverage, up to 0.5 monolayers, water does not dissociate and an intact water species is observed above 160 K, which is characterized by an O 1s binding energy 0.6 eV higher than that of chemisorbed water and a high desorption temperature similar to the partially dissociated layer. The extra stabilization is most likely due to hydrogen bonds with atomic oxygen.
在超高真空条件下，使用基于同步加速器的光电子能谱和光吸收光谱研究了 Rh{111}表面上水和氧气的共吸附。在低于 154 K 的温度下，水在清洁表面上完整吸附。然而，用 X 射线辐照会导致快速离解和形成混合 OH+H(2)O 层，表明部分离解层在热力学上更稳定。在覆盖度低于 0.3 单层的情况下共吸附水和氧气具有类似的效果，导致水和羟基分子以 3:2 的比例形成氢键网络。部分离解层比化学吸附完整的水更稳定，最大脱附温度高达 30 K。对于更高的氧气覆盖度，高达 0.5 单层，水不会离解，在 160 K 以上观察到完整的水物种，其 O 1s 结合能比化学吸附水高 0.6 eV，脱附温度与部分离解层相似。额外的稳定性很可能是由于与原子氧的氢键。
