CNR-IOM DEMOCRITOS, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche , Via Bonomea 265, 34136 Trieste, Italy.
Center for Green Research on Energy and Environmental Materials (GREEN), National Institute for Materials Science (NIMS) , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
J Am Chem Soc. 2016 Sep 14;138(36):11560-7. doi: 10.1021/jacs.6b03446. Epub 2016 Aug 1.
Wet conditions in heterogeneous catalysis can substantially improve the rate of surface reactions by assisting the diffusion of reaction intermediates between surface reaction sites. The atomistic mechanisms underpinning this accelerated mass transfer are, however, concealed by the complexity of the dynamic water/solid interface. Here we employ ab initio molecular dynamics simulations to disclose the fast diffusion of protons and hydroxide species along the interface between water and ceria, a catalytically important, highly reducible oxide. Up to 20% of the interfacial water molecules are shown to dissociate at room temperature via proton transfer to surface O atoms, leading to partial surface hydroxylation and to a local increase of hydroxide species in the surface solvation layer. A water-mediated Grotthus-like mechanism is shown to activate the fast and long-range proton diffusion at the water/oxide interface. We demonstrate the catalytic importance of this dynamic process for water dissociation at ceria-supported Pt nanoparticles, where the solvent accelerates the spillover of ad-species between oxide and metal sites.
在多相催化中，湿条件可以通过协助反应中间体在表面反应位点之间扩散，从而显著提高表面反应的速率。然而，这种促进质量传递的原子机制被动态水/固界面的复杂性所掩盖。在这里，我们采用从头算分子动力学模拟来揭示质子和氢氧根物种沿着水和氧化铈之间界面的快速扩散，氧化铈是一种催化上重要的、高度可还原的氧化物。结果表明，在室温下，多达 20%的界面水分子通过质子转移到表面 O 原子而发生解离，导致部分表面羟化，并在表面溶剂化层中增加氢氧根物种。水介导的 Grotthus 样机制被证明可以在水/氧化物界面激活快速和长程质子扩散。我们证明了这种动态过程在氧化铈负载的 Pt 纳米颗粒上水离解中的催化重要性，其中溶剂加速了吸附物种在氧化物和金属位点之间的溢流。
