Transition metal phosphides (TMPs) are expected to be excellent electrocatalysts for oxygen evolution reaction (OER) because of their high stability, highly conducting metalloid nature, highly abundant constituting elements, and the ability to act as a precatalyst due to in situ surface-formed oxy-hydroxide species. Herein, a "one-pot" colloidal approach has been used to develop a rod-shaped one-dimensional non-noble metal FeCoP electrocatalyst, which exhibits an excellent OER activity with an exceptionally high current density of 950 mA cm-2, a turnover frequency value of 7.43 s-1, and a low Tafel slope value of 54 mV dec-1. The FeCoP electrocatalyst affords OER ultralow overpotentials of 230 and 260 mV at current densities of 50 and 100 mA cm-2, respectively, in 1.0 M KOH, and demonstrates a superior catalytic stability of 10,000 cycles and durability up to 60 h at 50 mA cm-2. An insight into the superior and stable electrocatalytic OER performance by the FeCoP nanorods is obtained by extensive X-ray photoelectron spectroscopy, X-ray diffraction, Raman and infrared spectroscopy, and cyclic voltammetry analyses for a mechanistic study. This reveals that a high number of electrocatalytically active sites enhance the oxygen evolution and kinetics by offering metal ion sites for utilitarian in situ surface formation and adsorption of *O, *OH, and *OOH reactive species for OER catalysis.
Keywords: electrocatalyst; electrolysis; iron cobalt phosphide; nanorods; oxygen evolution reaction.