We grow vertically aligned single crystalline Ta2O5 nanorod arrays that can be converted to Ta3N5 nanorod arrays by nitridation. Combined with cobalt phosphate (Co-Pi) as a co-catalyst, such Ta3N5 nanorod photoanodes can yield photocurrent densities of ∼3.6 mA cm(-2) at 1.23 VRHE and ∼8.2 mA cm(-2) at 1.59 VRHE under AM 1.5G (100 mW cm(-2)) irradiation.