Deconvoluting Competing Adsorbate Evolution, Single- and Dual-Lattice Oxygen OER Pathways in Iron-Doped Nickel Layered Double Hydroxides

Nickel–iron layered double hydroxides are efficient nonprecious oxygen evolution reaction (OER) electrocatalysts, although their complex lattice oxygen-related OER mechanisms lack quantitative discrimination of the adsorbate evolution mechanism (AEM), single-lattice oxygen mechanism (SLOM), and dual-lattice oxygen mechanism (DLOM). Herein, we adopt in situ isotopic differential electrochemical mass spectrometry to quantitatively resolve these competing pathways via iron doping and potential modulation. The iron content and overpotential jointly regulate multipathway OER behaviors. This work clarifies long-standing mechanistic ambiguities and provides atomic-scale guidance for optimizing non-noble OER electrocatalysts.