Hybrid zirconium phosphate phosphonates as efficient hosts for confined Ni–Fe oxygen evolution catalysts

The rational design of earth-abundant electrocatalysts for the oxygen evolution reaction (OER) requires materials platforms capable of stabilizing catalytically active species under strongly alkaline conditions while maintaining efficient charge-transfer pathways. Here, we report a family of amino acid-derived zirconium phosphate–phosphonate hybrid materials that act as structurally tunable layered hosts for the confinement of Ni2+ and Fe3+ ions. Amino acid functionalization promotes exfoliation of the layered framework into colloidal nanosheets, enabling homogeneous metal dispersion within well-defined organic–inorganic interfaces. Systematic variation of the ligand structure and Ni/Fe composition reveals clear correlations between supramolecular organization, interfacial metal coordination, and electrocatalytic performance. The glycine-derived material (ZGLY) with an optimized Ni/Fe ratio achieves an overpotential of 304 mV to reach a geometric current density of 10 mA cm−2 and a Tafel slope of 32.9 mV dec−1, together with sustained stability in alkaline media, exhibiting enhanced activity and overall performance compared to previously reported zirconium phosphate-based OER systems. Post-operando Raman spectroscopy and XPS unambiguously identify NiOOH and FeOOH formed in situ as catalytically active phases, while XRD and electron microscopy confirm that the ZPAC scaffold preserves its structural integrity throughout the operation. These observations indicate that the ZPAC framework primarily acts as a chemically robust host, enabling the stabilization and spatial confinement of the catalytically active Ni–Fe oxyhydroxide species formed under operating conditions. Consequently, these findings highlight zirconium phosphate–phosphonates as versatile 2D hybrid materials, in which the chemical composition, interlayer organization, and metal confinement can be tuned to regulate catalytic behavior, providing new insights into the design of durable, earth-abundant water oxidation catalysts.