Photo-assisted synthesis of zinc-iron layered double hydroxides/TiO2 nanoarrays toward highly-efficient photoelectrochemical water splitting

A highly-matched semiconductor/cocatalyst is crucial to enhance the bulk charge separation and surface reaction kinetics of the photoelectrode in the solar water splitting system. In this work, well-aligned, hierarchical zinc-iron layered double hydroxide (LDH) is in situ synthesized on the surface of TiO2 by a facile and effective photo-assisted electrodeposition(PED) method. An experimental-computational combination study reveals that the photogenerated holes of TiO2 tend to travel to ZnFe-LDH which enhances the bulk charge separation; while ZnFe-LDH acts as a cocatalyst which accelerates the surface water oxidation reaction. The resulting TiO2/ZnFe-LDH-PE photoanode exhibits a largely enhanced PEC performance: the photocurrent density at 1.0 V vs. RHE is 2.29 and 1.31 times higher than that of the pristine TiO2 and TiO2/ZnFe-LDH-E (prepared by a conventional electrosynthesis method) photoanode, with 150 mV and 50 mV of negative shift for onset potential. This can be ascribed to the enhanced interface interaction and highly-matched band structure between ZnFe-LDH and TiO2. It is expected that this strategy can be extended to other heterostructures for advanced performance in the fields of energy conversion and storage.