Ta 3 N 5 Nanosheets Derived from TaS 2 as Efficient Photocatalysts for Water Oxidation

The morphology and crystalline structure of semiconductor materials both play important roles in determining the photocatalytic activity of such materials. In this regard, tantalum nitride (Ta3N5) shows promise as a visible-light-responsive photocatalyst for solar-driven water splitting. Even so, the performance of this material is limited by its bulk morphology and by high defect densities and inefficient charge transport. The present work synthesized single-crystalline Ta3N5 nanosheets having reduced defect concentrations and an increased specific surface area via the direct nitridation of two-dimensional TaS2 nanosheets. The Ta3N5 nanosheets had a thickness of approximately 30 nm with well-defined exposed facets and a uniform single-crystalline structure, and so led to a shorter charge-carrier diffusion length along with efficient charge separation and transport. When modified with IrOx as a cocatalyst, these nanosheets provided an apparent quantum yield of 32.4% at 420 nm during photocatalytic oxygen evolution with sacrificial electron acceptors, outperforming Ta3N5 synthesized from Ta2O5. This material was also integrated into Z-scheme photocatalyst sheets together with La5Ti2Cu0.9Ag0.1O7S5 as the hydrogen evolution photocatalyst and carbon nanotubes as the electron mediator. These sheets enabled overall water splitting with stoichiometric H2 and O2 evolution in response to visible light, with a light absorption range extended to approximately 600 nm. This work underscores the critical roles of precursor selection and nanoscale morphological control in the development of photocatalysts with minimal defects and provides new insights expected to advance the field of solar-to-chemical energy conversion.