Hollow-Co3O4@CoP/NS-RGO Heterojunction Structure Derived from ZIF-67 Promotes Hydrogen Evolution Reaction and Oxygen Evolution Reaction Bifunctional Catalysis

In this work, a two-step calcination method to fabricate Co3O4@CoP hollow nanoparticles embedded in N, S-co-doped reduced graphene oxide substrates is reported. The electrocatalyst is synthesized through a hydrothermal-calcination method of adding graphene oxide using ZIF-67 as a template followed by an annealing process in the presence of NaH2PO4·H2O. In the designed electrocatalyst, the formed hollow nanoparticles had an average diameter of 100 nm. The synthesized electrocatalyst displays a hydrogen evolution reaction overpotential of 54 mV at 10 mA cm–2 current density in 0.5 mol L–1 H2SO4 solution at room temperature, comparable to Pt/C catalysts. The oxygen evolution reaction overpotential in 1 mol L–1 KOH electrolyte is 288 mV, which is almost equivalent to that of IrO2. Stated thus, the as-prepared composite catalysts are promising candidates for bifunctional catalysts for water splitting technology, relieving the limitation of commercial catalysts caused by their single catalytic performance.