Prismatic Ta3N5-composed spheres produced by self-sacrificial template-like conversion of Ta particles via Na2CO3 flux

Abstract

Spatial charge separation on the anisotropic facets of photocatalyst particles can enhance their photocatalytic performance by reducing the probability of electron–hole recombination. This study investigated the Na₂CO₃ flux growth of faceted Ta₃N₅ crystals using Ta powders as the Ta source. An extremely small amount of Na₂CO₃ flux led to the growth of well-formed prismatic Ta₃N₅ crystals as a single-phase. The prismatic crystals formed spherical aggregates with a size and shape similar to those of the raw Ta powders. Although Ta₃N₅ crystals were also grown from Ta₂O₅ and TaCl₅ in Na₂CO₃ flux, the products were neither well-formed particles nor single-phase Ta₃N₅, which suggests that Ta powder dissolved more easily in Na₂CO₃ flux. The growth mechanism of the spherical Ta₃N₅ aggregates was investigated by evaluating the crystal growth at different heating temperatures and times. Cross-sectional observation of the products indicated that the raw Ta powder grains acted as a self-sacrificial template, thus determining the size and shape of the final product. The Ta₃N₅ crystals modified with CoO_x co-catalysts exhibited photocatalytic activity for O₂ evolution under visible light irradiation.