Effective catalysts, such as transition metal oxides (e.g., RuO2 and IrO2) or perovskites, exhibit a fine balance between strong enough binding to facilitate intermediate formation and weak enough binding to allow desorption of O2 thus achieving an optimal overpotential. The mechanistic pathway for OER varies depending on the electrolyte (acidic or alkaline) and the catalyst surface . In acidic media, the OER proceeds through the electrochemical oxidation of water, involving steps such as in equation .