Novel porous metal phosphonates as efficient electrocatalysts for the oxygen evolution reaction

Recently, metal-doped organic-inorganic hybrid nanomaterials have attracted substantial attention for their high catalytic activity in the electrochemical oxygen evolution reaction (OER). Here, we report three novel porous metal phosphonates, cobalt phosphonate (CoPIm), nickel phosphonate (NiPIm), and nickel-cobalt phosphonate (NiCoPIm), using iminodi(methylphosphonic acid) as an organophosphorous precursor via a hydrothermal nontemplated synthetic route. All three materials have been explored as electrocatalysts for the OER. Notably, the CoPIm material exhibits excellent electrocatalytic behavior among all of the as-prepared catalysts. The high surface area and the formation of active CoOOH species on the catalyst surface during the OER process are the main driving force for a superior electrochemical OER. The CoPIm catalyst requires a very small overpotential (334 mV) to reach the current density of 10 mA cm⁻² in 1.0 M KOH solution with a Tafel slope of 58.6 mV dec⁻¹ as compared to NiPIm, NiCoPIm, and commercial IrO₂. Additionally, the prepared CoPIm catalyst shows excellent stability up to 25 h, suggesting its potential in electrochemical water splitting.