Fundamental investigations into the activity and stability of earth-abundant bimetallic catalysts for the oxygen evolution reaction

Quantifying electrocatalyst degradation under realistic operating conditions remains a major challenge for the development of stable, earth-abundant oxygen evolution reaction (OER) anodes. Here, we establish laboratory‐scale methods to measure Fe dissolution from FeOOH in strongly alkaline electrolyte (14 M KOH, pH 15.8) at 1.5–2.0 VRHE, combining acid–base titration and X‐ray fluorescence spectroscopy to achieve full Fe mass balances across the electrode, electrolyte, and precipitates. Steady‐state FeOOH anodes exhibit dissolution rates of 0.15–0.30 mgFe cm⁻² h⁻¹ near the OER onset (∼1.75 VRHE), corresponding to <5 % of the total current, indicating that Faradaic efficiency alone cannot assess stability. Measurements with an Fe pseudo‐reference electrode suggest a non‐Faradaic dissolution pathway that persists even when current densities of ∼100 mA cm⁻² are maintained for >50 h. We further examine bimetallic FeM₂ (M₂ = Sn, Hf, Mn, Se) alloys prepared by electrodeposition. Across compositions, dissolution rates exceed those of pure Fe and scale with Tafel slope, implicating surface charge segregation as a key determinant of lattice stability. More electronegative alloying elements stabilize Fe⁴⁺, lower OER onset potentials and slow dissolution; while less electronegative elements produce hydroxyl‐rich, more reduced surfaces and accelerate loss. Spin‐polarized DFT+U calculations on FeOOH and FeSnOOH supercells reveal that Sn stabilizes Fe⁴⁺ but increases charge separation, consistent with improved kinetics yet higher dissolution rates. These findings provide design criteria for durable Fe‐based OER anodes: alloy with elements more electronegative than Fe that favor a 4+ oxidation state, while engineering homogeneous surface charge to suppress non‐Faradaic Fe loss. The methodology enables quantitative, mechanistically informed stability assessment across a broad range of catalytic materials.