Efficient carrier separation is important for improving photoelectrochemical water splitting. Here, the morphology modification and band structure engineering of Ta₃N₅ are accomplished by doping it with Cu and Zr using a two-step method for the first time. The initially interstitially-doped Cu atoms act as anchors to interact with subsequently doped Zr atoms under the influence of differences in electronegativity. This interaction results in Cu,Zr_g–Ta₃N₅ having a dense morphology and higher crystallinity, which helps to reduce carrier recombination at grain boundaries. Furthermore, the gradient doping of Zr generates a band edge energy gradient, which significantly enhances bulk charge separation efficiency. Therefore, a photoanode based on Cu,Zr_g–Ta₃N₅ delivers an onset potential of 0.38 V_RHE and a photocurrent density of 8.9 mA cm⁻² at 1.23 V_RHE. Among all the Ta₃N₅-based photoanodes deposited on FTO, a Cu,Zr_g–Ta₃N₅-based photoanode has the lowest onset potential and highest photocurrent. The novel material morphology regulation and band edge position engineering strategies described herein provide new ideas for the preparation of other semiconductor nanoparticles to improve the photoelectrochemical water splitting performance.