Revealing the facet-dependent dynamic reconstruction of NiFe-LDH for enhanced water oxidation

The oxygen evolution reaction (OER) limits water electrolysis efficiency, partly because active surfaces restructure under bias. This work reveals how crystal facets govern this operando reconstruction in NiFe-layered double hydroxides. By a temperature-controlled post-calcination strategy that preserves morphology and composition, either the (202) or (204) facet is selectively enriched, isolating crystal orientation as the sole variable. Using in situ Raman spectroscopy, the (202) facet is shown to reconstruct to active NiOOH at a much lower onset potential than the (204) facet. Density functional theory reveals that the (202) facet has a d-band center closer to the Fermi level and a higher density of states, optimizing intermediate adsorption and lowering the reaction barrier. Consequently, the (202)-rich catalyst exhibits a smaller Tafel slope and a 3.2-fold higher turnover frequency, outperforming commercial IrO 2 . Key advances include decoupling facet effects from morphological confounders and establishing facet-resolved electronic descriptors that predict OER activity.