Self-Assembly-Driven Nanodot Confinement and Interfacial Engineering of Cobalt Metaphosphates for Electrocatalytic Oxygen Evolution

Abstract

Metal phosphates possess attractive structural and electronic characteristics for the oxygen evolution reaction (OER) in alkaline media, yet their application is often limited by poor electrical conductivity and insufficient control over active-site exposure. Here we demonstrate a self-assembly-driven nanodot confinement and interfacial engineering strategy to construct carbon-supported cobalt metaphosphate nanodots (ComP/C), in which a pre-organized cobalt–phosphonic acid micellar template enables intimate integration between cobalt metaphosphate and a conductive carbonaceous nanosheets during thermal conversion. By tuning the pyrolysis temperature and duration, cobalt metaphosphate species evolve from ultrasmall nanodots to larger crystals, accompanied by systematic changes in carbon microstructure and cobalt–phosphate coordination. Electrochemical measurements reveal a pronounced size–activity relationship, with nanodot-confined cobalt metaphosphate delivering enhanced OER activity in alkaline electrolyte. Theoretical analysis further indicates that metaphosphate-induced electronic modulation combined with nanodot confinement effectively lowers OER kinetic barriers. These results demonstrate that nanoscale spatial confinement and phosphonate-mediated interfacial engineering, rather than composition alone, govern the electrocatalytic OER performance of cobalt metaphosphates, highlighting self-assembly-enabled metaphosphate nanodots as a promising platform for alkaline oxygen evolution.