Hybrid Zirconium Phosphate Phosphonates as Efficient Hosts for Confined Ni-Fe Oxygen Evolution Catalysts

Abstract

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 partial exfoliation of the layered framework into colloidal nanosheets, enabling homogeneous metal dispersion within well-defined organic-inorganic interfaces. Systematic variation of 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 a current density of 10 mA cm -2 at an overpotential of 304 mV and a Tafel slope of 32.9 mV dec -1 , together with sustained stability in alkaline media, exhibiting enhanced activity and stability compared to previously reported zirconium phosphate-based OER systems. Post-operando analyses indicate the in situ formation of NiOOH-type active phases, which remain spatially stabilized within the phosphate-phosphonate scaffold, limiting aggregation and preserving activity. These results highlight zirconium phosphatephosphonates as versatile 2D hybrid materials in which 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.