Two-dimensional metal-organic framework-derived selenium-doped cobalt Sulfide@Graphene nanofoam for oxygen electrocatalysis

Herein, we report an in-situ recrystallization strategy for preparing two-dimensional metal-organic framework uniformly anchored on graphene sheets, and further design selenium-doped cobalt sulfide@graphene nanofoam via the anion doping as a highly efficient bifunctional oxygen catalyst. Doping selenium atoms into cobalt sulfide not only is favourable for accelerating the transition from *OH to *O via increasing the electron density around cobalt centers, but also induces the formation of effective metal-oxygen and selenite/selenate species, resulting in significantly increasing the oxygen evolution reaction activity without the obvious deterioration of the oxygen reduction reaction activity. Moreover, graphene nanofoam supports with hierarchical porosity and high crystallinity provide large ion-accessible surface area for sufficiently exposing active sites to the electrolyte and prevents the deactivation of active sites via the formation of a 3-e5 layered graphene at the surface as a protective layer. Hence, a superior catalytic performance is achieved with a comparable mass activity to Pt/C catalyst and an overpotential of 347 mV at 10 mA cm(-2) for the oxygen evolution reaction. This work gives an insight into the design of efficient and robust first-row transition-metal electrocatalysts via structural engineering and anionic doping. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study presents an in-situ recrystallization strategy to prepare two-dimensional metal-organic framework anchored on graphene sheets, and a selenium-doped cobalt sulfide@graphene nanofoam as an efficient bifunctional oxygen catalyst. The graphene nanofoam support with hierarchical porosity and high crystallinity provides a large ion-accessible surface area to expose active sites to the electrolyte and prevent deactivation of active sites.