<p>Activating the lattice oxygen of catalysts can accelerate the oxygen evolution reaction. However, a fundamental understanding of the lattice oxygen dynamics remains insufficient, which ultimately impairs catalyst development. Herein, we show that a CO₃^2--containing electrolyte can substantially alter the reactivity and redox stability of lattice oxygens. In particular, for CoOOH and NiCoOOH, which feature high lattice oxygen reactivity, higher degrees of CO₃^2- intercalation deactivate lattice oxygen, shifting the reaction pathway from the lattice oxygen mechanism to the adsorbate evolution mechanism. <i>Operando</i> spectroscopic and spectrometric analyses coupled with ¹⁸O isotopic labeling corroborate the decreased metal‒oxygen bond covalency and hindered lattice oxygen release caused by the intercalation of CO₃^2-. Importantly, the catalysts with a fine-tuned degree of CO₃^2- intercalation maintain high activity and stability owing to the dynamic equilibrium between lattice oxygen release and refilling, demonstrating negligible degradation in an alkaline water electrolyzer after 5000 h of operation at 0.5 A cm^-2. This work reveals the intricacy of lattice oxygen dynamics, offering opportunities for designing high-performance electrocatalysts for real-life applications.</p>