Development of a Core–Shell Heterojunction Ta₃N₅-Nanorods/BaTaO₂N Photoanode for Solar Water Splitting

Heterostructure-based photoanodes have been investigated to enhance light absorption and promote the generation and extraction of charge carriers for efficient solar-to-hydrogen energy conversion. Oxy(nitride) semiconducting materials are promising candidates to harvest the visible solar spectrum; however, the realization of stable and efficient oxy(nitride) heterostructure-based photoanodes remains a challenge. Here, we demonstrate a core–shell heterojunction photoanode of Ta3N5-nanorods/BaTaO2N that is obtained by combining glancing angle deposition and dip coating techniques. The heterojunction photoanode homogeneously covered by a FeNiOx cocatalyst (Ta3N5-NRs/BaTaO2N/FeNiOx) generates a stable photocurrent of ∼4.5 mA cm–2 at 1.23 VRHE under simulated AM 1.5G sunlight. The stoichiometric evolution of O2 and H2 from water occurs steadily over an hour when the covered heterojunction photoanode is connected to a Pt counter electrode with faradaic efficiencies of 90%–95%. This work may open a new path to fabricating efficient and stable oxy(nitride) photoactive materials for solar energy conversion.