Precise Control of Layer Number in High-Entropy LDH: Impact on Lattice Oxygen Activity and Water Oxidation Performance

Two-dimensional (2D) high-entropy layered double hydroxides (HE LDHs) are emerging as a new platform for the design of efficient and robust water oxidation electrocatalysts. However, a significant challenge remains in precisely controlling the number of layers in 2D HE LDHs and elucidating the impact of the layer number on the oxygen evolution reaction (OER) pathway. Here, we demonstrate a top-down liquid-phase exfoliation method to precisely control the layer number of quaternary to septenary HE LDHs within 1–3 layers, such as a typical MnFeCoNiCu LDH. Exfoliated monolayer MnFeCoNiCu LDH exhibits superior OER performance, achieving a low overpotential of 234 mV and an ultralow Tafel slope of 32.1 mV dec–1 at 10 mA cm–2 in 1.0 M KOH, exceeding commercial IrO2 and most advanced monolayer OER catalysts. This catalyst shows exceptional stability, exhibiting sustained activity for 1000 h at a high current density of ∼100 mA cm–2. Significantly, the enhanced catalytic activity arises not solely from an increased electrochemically active surface area but predominantly from a shift in the OER mechanism. This transition, from the conventional adsorbate evolution mechanism to the lattice oxygen oxidation pathway, is supported by advanced spectroscopic techniques and density functional theory calculations. This research not only introduces a novel synthetic strategy for the fabrication of monolayer HE LDH but also presents innovative approaches for activating lattice oxygen within these materials, thereby enabling efficient and stable water oxidation.