Aerosol synthesis of shape-controlled template particles: a route to Ta3N5 nanoplates and octahedra as photocatalysts

Abstract

Metal oxynitrides and nitrides are important materials for use as photocatalysts due to their ability to absorb visible light in comparison to their oxide counterparts. The photoactivity of these materials should be enhanced through shape-controlled particles and nanostructuring; however, facile syntheses to high fidelity shape control are rare. Here, the syntheses of porous Ta₃N₅ nanoplates and octahedra are reported through nitridation of aerosol-prepared template particles. Specifically, amorphous nanoplates and octahedra with a nominal composition of Ta₂O₅ were prepared selectively by aerosol-assisted molten salt syntheses (AMSS) through the use of different fluxes. The amorphous nature of the products from AMSS is surprising given their defined shape, yet the use of these templates decreased the nitridation time to Ta₃N₅ compared to most reports, resulting in a product with fewer surface defects. Moreover, the structure-controlled Ta₃N₅ samples yielded enhanced photocatalytic performances for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) compared to structurally ill-defined Ta₃N₅. Significantly, other metal oxynitrides or nitrides with defined nanoscale features and enhanced photoactivity should be possible through this synthetic approach.