Rational design of metal organic framework derived porous Au@Co 3 O 4 /C nanocomposite materials for the electrochemical overall water splitting

To meet the demand for renewable energy, it is urgently necessary to develop a bifunctional electrocatalyst that is effective and accessible for both the hydrogen evolution process and the oxygen evolution through overall water splitting. In this current work a series of hybrid nanocomposite materials of gold nanoparticles embedded porous carbon supported cobalt oxides have been fabricated by a rapid one-step carbonization route from Zeolitic Imidazolate Framework (ZIF-67), cobalt based metal–organic-framework. The MOF derived Au@ ZIF Nano Particles electrocatalyst materials displayed significant activities with low overpotentials. Among the synthesised catalysts, Au 8.0 @C/Co 3 O 4 (A8ZNP) catalyst showed superior activity with very low overpotentials (η) of 0.452 V in Oxygen Evolution Reaction (OER) and 0.482 V in Hydrogen Evolution Reaction (HER) at 10 mA cm −2 also 74.7 mV dec −1 and 76.1 mV dec −1 Tafel slope values respectively. Catalyst A8ZNP also exhibited approximately 7 times more current density than that of Co 3 O 4 @C or ZIF Nano Particles (ZNPs) at fixed overpotentials in both OER and HER processes. These obtained results were superior in many cases compared to the most reported gold doped conventional Co 3 O 4 . Besides superior catalytic activity, in chronoamperometry, the A8ZNP catalyst demonstrated outstanding stability with a significant current retention of 0.243 mA cm −2 over a lengthy duration of 4000 s. The enhanced OER and HER activities and catalytic stability of A8ZNP attributed to large Electrochemical active surface Area of 1.81 mF cm −2 and synergistic interaction between gold Nanoparticles and porous ZNPs. The thorough investigation presented in the current work offers fresh perspectives on the creation of effective bifunctional catalysts for the electrochemical overall water splitting reaction. Graphical abstract