The water oxidation reaction plays a major role in many alternative-energy systems because it provides the electrons and protons required for the use of renewable electricity. We report the tuning of the iron molybdate (FeMoO4) electron structure via a coupled interface between the catalytic centers and the substrate. Our developed FeMoO4 catalysts can provide a 50 mA cm-2 current density at 1.506 V vs. RHE with excellent stability in 1.0 M KOH. The improved performance can be ascribed to the synergy of the optimized electronic structures and hierarchical nanostructure.