Ge‐Mediated Modification in Ta 3 N 5 Photoelectrodes with Enhanced Charge Transport for Solar Water Splitting

Ta 3 N 5 is a promising photoanode candidate for photoelectrochemical water splitting, with a band gap of about 2.1 eV and a theoretical solar‐to‐hydrogen efficiency as high as 15.9 % under AM 1.5 G 100 mW cm −2 irradiation. However, the presently achieved highest photocurrent (ca. 7.5 mA cm −2 ) on Ta 3 N 5 photoelectrodes under AM 1.5 G 100 mW cm −2 is far from the theoretical maximum (ca. 12.9 mA cm −2 ), which is possibly due to serious bulk recombination (poor bulk charge transport and charge separation) in Ta 3 N 5 photoelectrodes. In this study, we show that volatilization of intentionally added Ge (5 %) during the synthesis of Ta 3 N 5 promotes the electron transport and thereby improves the charge‐separation efficiency in bulk Ta 3 N 5 photoanode, which affords a 320 % increase of the highest photocurrent comparing with that of pure Ta 3 N 5 photoanode under AM 1.5 G 100 mW cm −2 simulated sunlight.