Photodeposition of Fe-Based Cocatalysts Capable of Effectively Promoting the Oxygen Evolution Activity of BaTaO2N

Activation of narrow bandgap photocatalysts is a prerequisite for the efficient production of renewable hydrogen from water using sunlight. Loading of dual cocatalysts intended to promote reduction and oxidation reactions by photodeposition is known to greatly enhance the water splitting activity of certain oxide photocatalysts. However, it is difficult to photodeposit oxygen evolution cocatalysts onto narrow bandgap oxynitride photocatalysts because the driving forces for the necessary oxidation reactions are weak. The present work demonstrates oxidative photodeposition of the Fe-based cocatalyst FeOx onto a Mg-doped BaTaO2N photocatalyst having an absorption edge wavelength of 620 nm. This modification enhances the oxygen evolution activity of the photocatalyst more effectively than conventional impregnation methods. The rapid removal of photoexcited electrons from the photocatalyst by a reduction cocatalyst (Pt) and an electron acceptor (molecular oxygen) are evidently necessary for the photodeposition of the FeOx cocatalyst. A Mg-doped BaTaO2N photocatalyst coloaded with Pt and FeOx exhibits an apparent quantum yield of 1.2% at 420 nm during the oxygen evolution reaction in an aqueous AgNO3 solution. This photodeposition procedure does not involve any heat treatment and so provides new opportunities for the design and construction of oxygen evolution sites on narrow-bandgap non-oxide photocatalysts that may be prone to thermal decomposition.