The constantly increasing global energy demand and related environmental issues urgently motivate the pursuit of renewable and eco-friendly energy sources [1].Artificial photosynthesis that converts solar energy into storable chemical fuels is an attractive way to produce green and sustainable energy, as well as to address the intermittency of solar energy [2,3].Solar-driven photoelectrochemical (PEC) water splitting is one of principal artificial photosynthesis processes to produce sustainable hydrogen.Tantalum nitride (Ta3N5) with a theoretical maximum solar conversion efficiency of 15.9％ has emerged as one of the most promising photoanode materials for solar-driven water oxidation [4-7].However, the highest applied bias photon-to-current efficiency achieved so far is only 2.72％.Various strategies have been proposed to improve the PEC water oxidation performance of Ta3N5 photoanodes, including nanostructuring, surface modification with cocatalysts or passivation layers, and doping with foreign elements (such as Ba, Mg, Zr, Sc, and Na) [8].Although the introduction of foreign ion dopants, such as Mg-Zr or Sc [9,10], can lower the onset potential of Ta3N5 photoanodes, the photocurrent density is far below its theoretical value, mainly due to poor carrier transport.