Rational Design of α-MoO3 Nanoflowers over Co3O4 Nanowire Arrays with Enhanced Active Site Exposure for High-Performance Water Oxidation

Developing effectual, stable, and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) remains pivotal for advancing sustainable hydrogen production via electrochemical water splitting. Herein, we report the rational design of Co3O4 nanowire arrays hierarchically decorated with α-MoO3 nanoflowers (Co3O4@α-MoO3) grown directly on nickel foam via a scalable hydrothermal strategy. By optimizing MoO3 loading, the Co3O4@α-MoO3-2 heterostructure achieves an ultralow overpotential of 209 mV at 10 mA cm−2, a Tafel slope of 60 mV dec−1, and superior charge-transfer kinetics in 1 M KOH. Comprehensive analysis reveals that the synergistic interfacial coupling enhances electronic conductivity, exposes abundant active sites (ECSA = 1106.50 cm2), and optimizes OER intermediate adsorption through mixed valence Co/Mo centers and oxygen defects. This work elucidates morphology–composition synergy in oxide heterostructures, offering a blueprint for high-performance OER electrocatalysts.