• OER is the rate-limiting step in water electrolysis due to its sluggish four-electron kinetics, necessitating efficient electrocatalysts to reduce overpotential.
• The classic AEM and LOM mechanisms exhibit an inherent trade-off between stability and activity, which recent catalyst engineering aims to balance.
• Newly proposed OPM and COM mechanisms introduce dynamic surface reconstruction and photon-assisted catalysis, offering pathways to circumvent traditional rate-limiting steps.
• Systematic identification strategies—combining kinetic, experimental, and theoretical approaches—are essential for guiding mechanism-directed design of next-generation OER catalysts.