Hierarchical cobalt phenylphosphonate nanothorn flowers for enhanced electrocatalytic water oxidation at neutral pH

Cobalt-based phosphate/phosphonates are a class of promising water oxidation catalysts at neutral pH. Herein, we reported a facile hydrothermal synthesis of various nanostructured cobalt phenylphosphonates. It is found that the number of hydroxyl group of structure-directing reagent is crucial for the construction of 3D hierarchical structures including hierarchical nanosheet flower-like assemblies and nanothorn microsphere. These samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, infrared, and X-ray photoelectron spectroscopy techniques. They can act as highly efficient electrocatalysts for the oxygen evolution reaction at neutral pH. Among these, hierarchical cobalt phenylphosphonate nanothorn flowers present excellent performance, affording a current density of 1 mA cm −2 required a small overpotential of 393 mV. This work offers a new clue to develop high-performance metal phosphonate/phosphate catalysts toward electrochemical water oxidation.