Alkaline oxygen evolution: exploring synergy between fcc and hcp cobalt nanoparticles entrapped in N-doped graphene

Herein, we report a Mott-Schottky catalyst by entrapping cobalt nanoparticles inside the N-doped graphene shell (Co@NC). The Co@NC delivered excellent oxygen evolution activity with an overpotential of merely 248 mV at a current density of 10 mA cm–2 with promising long-term stability. The importance of Co encapsulated in NC has further been demonstrated by synthesizing Co nanoparticles without NC shell. The synergy between the hexagonal close-packed (hcp) and face-centered cubic (fcc) Co plays a major role to improve the OER activity, whereas the NC shell optimizes the electronic structure, improves the electron conductivity, and offers a large number of active sites in Co@NC. The density functional theory calculations have revealed that the hcp Co has a dominant role in the surface reaction of electrocatalytic oxygen evolution, whereas the fcc phase induces the built-in electric field at the interfaces with N-doped graphene to accelerate the H+ ion transport. A Mott-Schottky catalyst, Co encapsulated in N-doped graphene, has been demonstrated to be an excellent water oxidation electrocatalyst in comparison to co-nanoparticles. [Display omitted] •Facile synthesis of cobalt nanoparticles entrapped inside N-doped graphene shell (Co@NC).•Superior alkaline water oxidation activity of Co@NC over Co nanoparticles.•Synergy between fcc and hcp Co in Co@NC to improve water oxidation activity.•hcp Co provides the active surface sites for electrocatalytic oxygen evolution.