The development of sustainable hydrogen production technologies is critical to addressing the global energy crisis and environmental challenges. Among water electrolysis systems, anion-exchange membrane water electrolyzers (AEMWEs) have gained attention for their ability to combine cost-effectiveness with high efficiency. However, AEMWEs face challenges such as sluggish oxygen evolution reaction (OER) catalysts with low conductivity and density of active sites, especially with the feed stock of pure water. In this study, a tri-metal Prussian blue analogue (PBA) was synthesized at room temperature and employed as an efficient OER pre-catalyst. Electrochemical activation of this as-prepared material in the alkaline solution generates highly active and conductive crystalline-amorphous metal (oxy)hydroxides as the true catalytic sites, which exhibited exceptional OER performance with the overpotential of 251 mV at 10 mA·cm^–2 and stable operation for 500 h in the alkaline solution. When applied as anode in AEMWEs, it delivered 1 A·cm^–2 at 1.72 and 2.20 V with the feedstock of alkaline solution (1 M KOH) and pure water, respectively, demonstrating its large application prospect in AEMWE.