Conformal coating of ultrathin metal-organic framework on semiconductor electrode for boosted photoelectrochemical water oxidation

Exploring efficient photocatalysts for water oxidation is highly demanded because of their significant role in artificial photosynthesis. The research of metal-organic frameworks (MOFs) based photoelectrochemical (PEC) water splitting is promising but still in its infancy due to the challenge to fabricate high-quality MOFs photo-electrode. Here an Fe2O3/Fe-based MOF core/shell nanorod is prepared for efficient PEC water oxidation via a facile surfactant-assisted solvothermal method. With polyvinylpyrrolidone (PVP) molecules as intermedia, an ultrathin MOF shell of several nanometers thick can be controllably grown on the surface of Fe2O3 nanorod. Charge dynamical behaviors study by ultrafast transient absorption spectroscopy (TAS) and photoelectrochemical impedance spectroscopy (PEIS), reveal that the ultrathin MOF shell is crucial to promote the charge separation by providing a cascade band level, but also accelerate the hole injection efficiency via exposing more accessible Fe-oxo cluster active sites. Accompanied with good visible-light response, the Ti-doped Fe2O3/NH2-MIL-101(Fe) photoanode delivers a boosted photocurrent density of 2.27 mA cm(-2) at 1.23 V vs. RHE, which is about 2.3 folds of that of pristine Fe2O3. This study provides new insights into the rational design of semi-conductor/MOFs hybrid materials for photo/photoelectrochemical catalysis.