The development of efficient and reliable acidic oxygen evolution reaction (OER) electrocatalysts represents a crucial step in the process of water electrolysis. RuO₂, a benchmark OER catalyst, suffers from limited large-scale applicability due to its tendency toward the less stable lattice oxygen mechanism (LOM). This work reports the synthesis of Co-doped RuO₂ nanosheets with a unique porous morphology composed of interconnected grains via a facile molten salt method. Co doping modulates the grain size, effectively increasing the specific surface area and introducing oxygen vacancies. These oxygen vacancies, coupled with the Co dopants, form Co-O(V) motifs that tune the electronic configuration of Ru. This structural engineering promotes a shift in the OER mechanism from the detrimental LOM pathway to the more efficient adsorbate evolution mechanism (AEM), significantly enhancing the stability of the RuO₂ matrix in acidic environments. The optimized Co_0.108-RuO₂ catalyst exhibits a low overpotential of 214 mV at 10 mA cm^-2 and remarkable stability over commercial RuO₂ and undoped counterparts, owing to the synergistic effect of the increased surface area, Co-O(V) motifs, and favored AEM pathway. This strategy of utilizing Co doping to engineer morphology, electronic structure, and reaction mechanism offers a promising avenue for developing high-performance OER electrocatalysts.