Fabrication of a Robust Tantalum Nitride Photoanode from a Flame‐Heating‐Derived Compact Oxide Film

Photoelectrochemical (PEC) water splitting provides an attractive way of converting solar energy to hydrogen energy. To make this approach practical, it is crucial to develop strategies that can fabricate efficient photoelectrode with a scalable manner. Herein, we report a rapid flame heating method to prepare Ta2O5 precursor film for Ta3N5 photoanode. By varying the parameters of flame heating, rational control over the physicochemical nature of Ta2O5 precursor film can be realized. With the following nitridation treatment, the compact precursor film can be transformed into tight-knit Ta3N5-based nitride film which strongly stuck to the underlying conductive Ta substrate. Due to the intimate interfacial connections and reasonable conductivity achieved via the manipulation of the flame heating duration, an enhanced charge separation efficiency was obtained for the as-prepared Ta3N5 photoanode. Furthermore, with the help of a ferrihydrite layer, the photocurrent density for PEC water oxidation on the optimum Ta3N5 photoanode reached ca. 3.53 mA cm-2 at 1.23 V vs. RHE, which is among the best values for planar Ta3N5-based photoanode. This highlights the advantages of flame heating over the traditional heating method for preparing precursor film for further processing or functionalization.