Preparation of calcium tantalum oxynitride from layered oxide precursors to improve photocatalytic activity for hydrogen evolution under visible light

A new precursor route to prepare calcium tantalum oxynitride (CaTaO2N) was explored in an attempt to improve the photocatalytic activity for H2 evolution from water under visible light. CaTaO2N catalysts were prepared using either a layered metal oxide (e.g., RbCa2Ta3O10 or HCa2Ta3O10) or a bulk-type Ca-Ta oxide prepared by the polymerized complex (PC) method. CaTaO2N samples prepared from the layered oxides had a less-aggregated morphology and a bluer absorption edge than an analog from a PC-derived precursor, in addition to a lower density of anionic defects. Samples prepared from the layered oxide also showed an enhanced photocatalytic activity for H2 evolution from an aqueous methanol solution under visible light (λ > 420 nm), primarily because of their lower density of anionic defects and the enhanced driving force for surface redox reactions that resulted from their blue-shifted absorption edge.

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► A new precursor route to prepare CaTaO2N photocatalyst was studied.
► Physicochemical properties of CaTaO2N depended on the precursor oxide employed.
► Pt-loaded CaNbO2N photocatalyzed water reduction under visible light (λ > 420 nm).
► Layered RbCa2Ta3O10 was a better precursor than a bulk-type Ca-Ta oxide.