Rare Cobalt-Based Phosphate Nanoribbons with Unique 5-Coordination for Electrocatalytic Water Oxidation

Coordinatively asymmetric or unsaturated metal centers may serve as accessible active sites and allow strong interaction with incoming guests in catalysis, sensing, and separation applications. Herein, a peculiar Co-based phosphate NaCo4(PO4)3, in which all Co atoms were in very rare 5-coordinations, was first synthesized in nanoribbon morphology. With the combined merits of the unique Co coordination, intrinsic half-metallicity, and nanostructured morphology, NaCo4(PO4)3 nanoribbons were characterized with high efficiency for water oxidation in a neutral electrolyte, remarkably outperforming congeneric phosphates such as Na2CoP2O7 with 4-coordinated Co configurations and even comparable to the benchmark RuO2 nanoparticles. The high catalytic performance validates a great potential in exploiting inorganic nanostructures with coordinatively asymmetric or unsaturated metal centers for energy storage and conversion applications.