Seawater is widely abundant on Earth and is considered an “unlimited” resource for hydrogen production via water electrolysis. However, seawater electrolysis is challenging due to impurity-induced side reactions. A selective and durable electrocatalyst is highly desired, especially for the sluggish oxygen evolution reaction (OER). In this talk, I will present our recent efforts to develop such OER electrocatalysts. Specifically, we investigated FeMoₓOᵧ-derived materials. We quantified the Mo leaching process in the precursor and identified the active species after surface reconstruction. An overpotential of 313 mV was required to achieve 1.0 A cm⁻² in both simulated alkaline seawater (1 M KOH + 0.5 M NaCl) and high-chloride conditions (1 M KOH + 1.5 M NaCl). Notably, in actual alkaline seawater (1 M KOH + seawater), our electrocatalyst required only 321 mV to deliver the same current density and remained stable for 400 h. In addition, I will introduce promising approaches to scale up our electrocatalysts for high-current (A cm⁻²) seawater oxidation.