On-Site Growth of a TaON Nanoshell on ZrO₂ Particles for Photocatalytic Water Splitting

Low-dimensional nanostructuring has emerged as a promising approach to enhance the photocatalytic performance of transition metal oxynitrides, a class of widely investigated visible-light-responsive photocatalysts. Despite their potential, the synthesis of nanostructured oxynitride materials remains a great challenge. In this study, we present a novel NH₄Cl-assisted vacuum nitridation method for <i>in situ</i> growth of an ultrathin TaON layer on particulate ZrO₂, resulting in the formation of TaON@ZrO₂ core@shell nanostructures. By controlling the Ta metal content in the precursor, the thickness of the TaON shell can be adjusted within the range of 1-3 nm. Comprehensive Raman spectroscopy and EXAFS analyses confirm the successful synthesis of well-defined and phase-pure TaON nanocrystals. Compared to conventional bulk TaON particles, the nanostructured TaON@ZrO₂ exhibits significantly enhanced photocatalytic activity for visible-light-driven water splitting. Surface photovoltage measurements further demonstrate improved charge separation efficiency, which is attributed to the unique nanostructure design. This work not only provides a robust strategy for the controlled synthesis of TaON@ZrO₂ nanoparticles but also underscores the critical role of nanostructuring in optimizing the water splitting performance of oxynitride-based photocatalysts.