Template-Assisted Size Control of Polycrystalline BaNbO2N Particles and Effects of Their Characteristics on Photocatalytic Water Oxidation Performances

The photocatalytic water oxidation using solar irradiation is a sustainable way to convert a natural source to energy. The perovskite-type oxynitride BaNbO2N is a candidate photocatalyst for this process because its long-range light absorbance of up to ca. 740 nm leads to the high ability of energy conversion. However, it is necessary to improve its poor performance by optimizing the crystallographic characteristics, chemical formula, depositions of cocatalysts, and so on. In this study, we aimed to identify the dominant factors of the photocatalytic performance of BaNbO2N. We controlled the particle characteristics by nitriding size-controlled Ba5Nb4O15 crystals in sizes of 0.2–50 μm as sacrificial templates. Porous BaNbO2N secondary particles of different sizes were achieved, and they exhibited distinctive photocatalytic performances for O2 evolution with rates between 14.1 and 113.9 μmol·h–1, depending on the precursor size and nitriding time. By correlating the performance with the basal particle char...