Exceptionally Stable And Super‐Efficient Electrocatalysts Derived From Semiconducting Metal Phosphonate Frameworks.

Two new isostructural semiconducting metal‐phosphonate frameworks are reported. Co2[1,4‐NDPA] and Zn2[1,4‐NDPA] (1,4‐NDPA4− is 1,4‐naphthalenediphosphonate) have optical bandgaps of 1.7 eV and 2.5 eV, respectively. The electrocatalyst derived from Co2[1,4‐NPDA] as a precatalyst generated a low overpotential of 374 mV in the oxygen evolution reaction (OER) with a Tafel slope of 43 mV dec−1 at a current density of 10 mA cm−2 in alkaline electrolyte (1 mol L−1 KOH), which is indicative of remarkably superior reaction kinetics. Benchmarking of the OER of Co2[1,4‐NPDA] material as a precatalyst coupled with nickel foam (NF) showed exceptional long‐term stability at a current density of 50 mA cm−2 for water splitting compared to the state‐of‐the‐art Pt/C/RuO2@NF after 30 h in 1 mol L−1 KOH. In order to further understand the OER mechanism, the transformation of Co2[1,4‐NPDA] into its electrocatalytically active species was investigated. [ABSTRACT FROM AUTHOR]