Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
J Am Chem Soc. 2012 Nov 21;134(46):19217-22. doi: 10.1021/ja308899g. Epub 2012 Nov 8.
Water-metal interfaces are ubiquitous and play a key role in many chemical processes, from catalysis to corrosion. Whereas water adlayers on atomically flat transition metal surfaces have been investigated in depth, little is known about the chemistry of water on stepped surfaces, commonly occurring in realistic situations. Using first-principles simulations, we study the adsorption of water on a stepped platinum surface. We find that water adsorbs preferentially at the step edge, forming linear clusters or chains, stabilized by the cooperative effect of chemical bonds with the substrate and hydrogen bonds. In contrast with their behavior on flat Pt, at steps water molecules dissociate, forming mixed hydroxyl/water structures, through an autocatalytic mechanism promoted by H-bonding. Nuclear quantum effects contribute to stabilize partially dissociated cluster and chains. Together with the recently demonstrated behavior of water chains adsorbed on stepped Pt surfaces to transfer protons via thermally activated hopping, these findings make these systems viable candidates for proton wires.
水-金属界面无处不在，在许多化学过程中发挥着关键作用，从催化到腐蚀。尽管已经深入研究了原子级平坦过渡金属表面上水的吸附层，但对于在实际情况下经常出现的阶梯表面上水的化学性质却知之甚少。本文使用第一性原理模拟研究了水在阶梯状铂表面上的吸附。我们发现，水优先在台阶边缘吸附，形成线性簇或链，通过与基底的化学键和氢键的协同作用稳定。与它们在平坦 Pt 上的行为相反，在台阶处，水分子通过氢键促进的自催化机制离解，形成混合的羟基/水结构。核量子效应有助于稳定部分离解的簇和链。结合最近在吸附于阶梯状 Pt 表面的水链上通过热激活跳跃传递质子的行为，这些发现使这些系统成为质子导线的可行候选者。
