Facile synthesis of hollow Co3O4-embedded carbon/reduced graphene oxides nanocomposites for use as efficient electrocatalysts in oxygen evolution reaction

Highlights: • ZIF-67/GO-W was synthesized by a facile precipitation reaction using water as solvent. • Small particle size and homogeneous distribution were realized in the ZIF-67/GO-W. • A novel hybrid nanostructure comprised of hollow Co₃O₄C/rGO-W is reported. • The hollow Co₃O₄C/rGO-W was used as electrocatalyst for oxygen evolution. • The hollow Co₃O₄C/rGO-W exhibits efficient electrocatalytic performance. -- Abstract: The development of non-noble-metal electrocatalysts that are both efficient and stable is of upmost important for the oxygen evolution reaction (OER) in renewable-energy technologies. In this study, cobalt-based zeolitic imidazolate frameworks wrapped by graphene oxide-water (denoted as ZIF-67/GO-W) were successfully prepared by a simple precipitate reaction using water as solvent. Due to the high dispersion of GO in aqueous solution, the synthesis of ZIF-67/GO-W enabled a smaller particle size of ZIF-67 to be attained, also resulted in a more homogeneous distribution between ZIF-67 and GO. Furthermore, a novel hybrid nanostructure comprised of hollow Co₃O₄-embedded carbon/reduced graphene oxides (Co₃O₄C/rGO-W) is achieved through a facile synthetic route involving the calcination-oxidation of ZIF-67/GO-W. The resulting nanocomposites were found to combine the high conductivity of graphene, the promising catalytic properties of the hollow Co₃O₄ nanoparticles and a homogeneous distribution of the ZIF-67/GO-W precursor. Enhanced OER activity and improved stability was therefore realized. The hollow Co₃O₄C/rGO-W was found to exhibit a low overpotential (382 mV) and a low tafel slope (62 mV dec⁻¹) in 0.1 M KOH, rendering them comparable to the commercial RuO₂ catalyst and an improvement to Co₃O₄ nanoparticles. This work presents an alternative strategy for the development of uniformly distributed ZIF-67/GO-W using water as solvent and suggests hollow Co₃O₄C/rGO-W as potential electrocatalysts for the OER in energy-related applications.