Unique Dynamics of Water Confined on the Surface of Metal Oxide Clusters

Abstract Water confined on metal oxide surface plays significant roles in heterogeneous catalysis. Heteropolyacid, a 1.2 nm‐metal oxide cluster with well‐defined structure, is applied as a model to understand the dynamics of water on its surface. The surface water strongly associates with heteropolyacid cluster and form the so‐called ‘pseudoliquid phase’ where catalytic reactions are conducted. Broadband dielectric spectroscopy and differential scanning calorimetry have been applied to probe the dynamics of water in this pseudoliquid phase. A supercooling phase transition of water below its normal melting temperature and a dipolar glassy relaxation behaviour due to the hindered dynamics of water have been observed. The rich dynamic behavior on the surface of such well‐defined metal clusters provide new perspectives to understand the properties of surface water and their relation to catalytic performance of heteropolyacid.