Hollow Polyhedral Arrays Composed of a Co₃O₄ Nanocrystal Ensemble on a Honeycomb-like Carbon Hybrid for Boosting Highly Active and Stable Evolution Oxygen

We synthesize hollow polyhedral arrays composed of honeycomb-like nanosheets of Co3O4 nanocrystals imbedded on carbon quantum dots (CQDs)- and nitrogen-codoped carbon matrix via a facile in situ air oxidation pyrolysis for CQDs-incorporated metal–organic framework polyhedral arrays. The function of CQDs hollowing and forming porous nanosheet shells was found. The resulting hierarchical architecture displays excellent oxygen evolution reaction activity with a low overpotential of 301 mV to drive 100 mA cm–2 in 1.0 M KOH and long-playing durability in oxygen evolution. The high performance can be ascribed to its highly dispersed Co3O4 nanocrystals, CQDs and nitrogen codoping, internal cavities, and hierarchical pore system.