WO₃ nanoneedles/α-Fe₂O₃/cobalt phosphate composite photoanode for efficient photoelectrochemical water splitting

We report the fabrication of the WO₃ nanoneedles/α-Fe₂O₃ heterojunction photoanodes for efficient photoelectrochemical water splitting. The high-aspect-ratio single crystalline WO₃ nanoneedles (NNs) act as both the photoanode framework and the light harvester in the UV and blue visible region. The porous layer of small α-Fe₂O₃ nanocrystals act as a cooperative light harvester in the visible region. The WO₃ NNs/α-Fe₂O₃ heterojunction photoanodes exhibit an extended light absorption band in the visible region and a significantly enhanced photocurrent density, which is ca. 1.6 times higher than that obtained on the pure WO₃ NNs. Cobalt phosphate (Co-Pi) was employed as an oxygen evolving catalyst to modify the heterojunction electrode, and the resulting WO₃ NNs/α-Fe₂O₃/Co-Pi composite photoanodes show an excellent photostability for oxygen evolution reaction.