Ge-Mediated Modification in Ta3N5 Photoelectrodes with Enhanced Charge Transport for Solar Water Splitting

Ta3N5 is a promising photoanode candidate for photoelectrochemical water splitting, with a band gap of about 2.1eV and a theoretical solar-to-hydrogen efficiency as high as 15.9% under AM 1.5G 100mWcm(-2) irradiation. However, the presently achieved highest photocurrent (ca. 7.5mAcm(-2)) on Ta3N5 photoelectrodes under AM 1.5G 100mWcm(-2) is far from the theoretical maximum (ca. 12.9mAcm(-2)), which is possibly due to serious bulk recombination (poor bulk charge transport and charge separation) in Ta3N5 photoelectrodes. In this study, we show that volatilization of intentionally added Ge (5%) during the synthesis of Ta3N5 promotes the electron transport and thereby improves the charge-separation efficiency in bulk Ta3N5 photoanode, which affords a 320% increase of the highest photocurrent comparing with that of pure Ta3N5 photoanode under AM 1.5G 100mWcm(-2) simulated sunlight.