<p>The design of efficient and durable electrocatalysts for acidic oxygen evolution remains a critical challenge. Recent advances have demonstrated that synergistic microstructure engineering and electrical resistance modulation can dramatically enhance the intrinsic activity and stability of acidic OER electrocatalysts. In this work, we systematically investigate the impact of fabrication methodology on the structure, morphology, and electrocatalytic properties of Co₃O₄ catalysts. Three representative techniques—ink-spraying, dip-coating, and drop-casting—were compared using a unified precursor and substrate framework. The ink-sprayed Co₃O₄ catalyst exhibits superior performance, achieving an overpotential of 386&#xa0;mV at 100&#xa0;mA·cm⁻², a Tafel slope of 51.5&#xa0;mV·dec⁻¹, and exceptional durability over 165&#xa0;h at 10&#xa0;mA·cm⁻² in 0.5&#xa0;M H₂SO₄. X-ray photoelectron spectroscopy (XPS) reveals a notable increase in the Co²⁺/Co³⁺ ratio and oxygen-vacancy concentration after long-term operation, indicating surface reconstruction and enhanced redox flexibility. Notably, the relative contribution of the oxygen-vacancy (O_V) component increases from 20.9% in the pristine state to 28.2% after 24&#xa0;h of OER operation. The uniform nanostructure, improved conductivity, and robust film adhesion endow the ink-sprayed electrode with both enhanced activity and stability, outperforming the dip-coated and drop-cast counterparts as well as most state-of-the-art Co-based OER catalysts reported in the literature. Furthermore, inductively coupled plasma mass spectrometry (ICP-MS) analysis confirms minimal metal leaching, highlighting the catalyst’s structural integrity and long-term stability. This work underscores the crucial role of fabrication methodology in tailoring catalytic performance and establishes ink-spraying as an efficient strategy for engineering high-performance Co₃O₄ catalysts suitable for acidic water electrolysis applications.</p> Graphical abstract <p></p>