Rational Design, Fabrication, and Mechanistic Study of High-Entropy FeCoNiZnMg-LDH Electrocatalysts for Efficient Water Splitting

Electrochemical water splitting still remains a cornerstone in sustainable hydrogen generation, but oxygen evolution reaction's (OER) kinetic inertia is related to the complex multi-step proton-coupled electron transfer and thermodynamic scaling of reaction intermediates. The efficiency of existing catalysts is only constrained by the linear scaling of intermediate adsorption energies under adsorbate evolution mechanism (AEM). For this purpose, activating lattice oxygen-mediated mechanism (LOM) has proven to be effective in introducing direct O–O bond formation and bypassing traditional energy barriers. Because lattice oxygen plays a key role, structural instability and cation leaching occur, leading to an intrinsic trade-off. We hypothesized that a high-entropy framework could reconcile these antagonistic properties by leveraging entropy-driven structural stabilization to support aggressive lattice oxygen participation. To address this, we design a quinary high-entropy FeCoNiZnMg layered double hydroxide (LDH) electrocatalyst by means of two different mechanisms: introducing d10 Zn as a lattice distorter to trigger a potential LOM-dominated mechanism by increasing the metal-oxygen covalency and, by using redox-inert Mg as a structural anchor to prevent lattice collapse. This high-entropy architecture is ideal for this work since its inherent configurational entropy and slow diffusion kinetically stabilize the active sites when oxygen is participating, both optimizing the efficiency and structural robustness. Utilizing a low-frequency pulse electrodeposition (PED) technique, we grew binder-free, hierarchical nanosheet arrays directly onto nickel foam. Crucially, the relaxation intervals inherent to this method regulated nucleation, yielding an open-porous architecture superior to that formed by static potentiostatic approaches. Advanced characterisation (XRD, XPS, XAFS) indicates that doping with d10 zinc severely distorts the lattice and renders the nickel environment electron-deficient. As evidenced by the operando Raman detection of oxygen radicals, this electronic tuning reinforces metal-oxygen covalency and provides compelling spectroscopic evidence supporting the participation of the LOM pathway. Conversely, redox-inert magnesium serves as a structural anchor; acting in concert with the high-entropy effect, it mitigates phase segregation and cation leaching. Consequently, the optimized catalyst achieves an industrial-grade current density of 100 mA cm⁻² at an ultralow 255 mV overpotential for oxygen evolution reaction (OER), maintaining resilience for over 100 hours. Besides that, the electronic structure modulation goes into the cathodic, where the catalyst has a hydrogen evolution reaction (HER) performance with an overpotential of 309 mV at 100 mA cm-2. Ultimately, this research validates the strategy of embedding inactive elements within high-entropy lattices to harmonize the activity-stability conflict in next-generation energy conversion.