In Situ Decorating Coordinatively Unsaturated Fe Sites for Boosting Water Oxidation Performance of TiO2 Photoanode

Kinetics play a critical role in the photoelectrochemical (PEC) system, whereas co-catalysis is mainly responsible for reducing the reaction barrier and facilitates water splitting. Here, the unsaturated Fe sites through the metal-organic framework (MOFs) structure promote the kinetics of water oxidation over TiO2 are successfully in situ decorated. This heterostructure further helps us to better understand the PEC behaviors of organic-inorganic hybrid systems. MIL-100(Fe), as the typical MOFs model, is facilely achieved by an FeOOH sacrificial template method, a strategy which could anchor the compact and ultrathin MIL-100(Fe) films on the surface of TiO2 to obtain abundant unsaturated Fe sites. The photocurrent density of MIL-100(Fe)/TiO2 reaches about 2.4 times at 1.23 V vs reversible hydrogen electrode (RHE) compared with bare TiO2, and the incident photon to current conversion efficiency value increases up to 47% (at 390 nm). Furthermore, the photocurrent density of MIL-100(Fe)/TiO2 is maintained at 84% after 3 h, showing that the organic component of MIL-100(Fe) takes a nature of favorable stability. The configuration of MIL-100(Fe)/TiO2 will bring a new insight for learning the basic function of unsaturated metal sites in the PEC system.