Photoelectrochemical (PEC) seawater splitting is regarded as a promising route for sustainable hydrogen production. However, its practical application is limited by the sluggish oxygen evolution reaction (OER) kinetics and the corrosion of photoanodes induced by high chloride ion concentrations. Herein, we report the construction of MoNiP layers on hematite (α-Fe₂O₃) photoanodes via a mild chemical deposition method, significantly enhancing both the stability and efficiency of seawater splitting. The incorporation of molybdenum modified the electronic structure of the photoanode, while PO_x^δ− and MoO_x^δ− surface species electrostatically repel chloride ions, effectively improving corrosion resistance. The optimized Fe₂O₃/MoNiP photoanode demonstrated a high photocurrent density of 3.63 mA·cm⁻² at 1.23 V vs. reversible hydrogen electrode (RHE). After 20 h of continuous operation in simulated seawater, the photocurrent exhibited minimal decay. Moreover, the H₂ and O₂ evolution rates were in near-stoichiometric proportions, ensuring high OER selectivity. This study highlighted the synergistic effect of Mo and NiP in regulating interfacial charge dynamics and suppressing side reactions, providing new insights for the design of robust and efficient photoanodes for PEC seawater splitting applications.