Reaction Packaging CoSe₂ Nanoparticles in N-Doped Carbon Polyhedra with Bifunctionality for Overall Water Splitting

Water electrolysis is a promising approach for green and large-scale hydrogen production; however, there are still challenges for developing efficient and stable bifunctional electrocatalysts toward the hydrogen and oxygen evolution reactions. Herein, zeolitic imidazolate framework-67 was used as the precursor for the construction of CoSe₂ nanoparticles trapped in N-doped carbon (NC) polyhedra. Among as-obtained CoSe₂-NC hybrid, highly active CoSe₂ nanoparticles in sizes of 10-20 nm are encapsulated in N-doped few-layer carbon shell, avoiding their easy aggregations of CoSe₂ nanoparticles as well as enhancing the long-term stability. The unique nanostructured CoSe₂-NC hybrid with a hierarchical porosity and 3D conductive framework thus fully exerts outstanding bifunctional catalytic activity of CoSe₂ centers. As a result, the CoSe₂-NC hybrid as bifunctional catalysts for overall water splitting delivers a high current density of 50 mA cm^-2 with an applied voltage of ∼1.73 V in an alkaline electrolyte, with a promising stability over 50 000 s.