Keggin-Type H₅PMo₁₀V₂O₄₀ Intercalated MgAl-LDH: Structural Integrity and Bifunctional Electrocatalytic Activity

The development of earth-abundant electrocatalysts is central to sustainable water electrolysis, yet many systems are limited by poor electronic conductivity and inadequate durability. In particular, the high solubility of discrete polyoxometalates (POMs) clusters hinders their direct deployment as stable heterogeneous electrocatalysts. Here, a Keggin-type H₅PMo₁₀V₂O₄₀ POM is intercalated into MgAl layered double hydroxide (MgAl-LDH) by a formamide-assisted exfoliation-reassembly strategy to afford a POM@MgAl-LDH hybrid. Structural characterization confirms quantitative ion exchange of POM anions into the LDH galleries and an increase of the basal spacing to 9.2-10.5 Å. Density functional theory calculations indicate thermodynamically favorable intercalation (ΔE ≈ -2.3 eV per formula unit) and predict an equilibrium interlayer distance that matches the experiment. The hybrid exhibits a BET surface area of 50.6 m² g^-1 and hierarchical porosity. In 1.0 M KOH, POM@MgAl-LDH functions as a bifunctional electrocatalyst, affording hydrogen and oxygen evolution overpotentials of 215 and 411 mV at 10 mA cm^-2, respectively, with ∼97% current retention over 12 h of electrolysis. These results suggest that spatial confinement of redox-active POM clusters within an earth-abundant MgAl-LDH host reduces POM loss into solution and improves the electrocatalytic response of LDH framework, offering a practical route to nonprecious-metal bifunctional electrocatalysts for alkaline water splitting.