IrNi nanoparticle-decorated flower-shaped NiCo2O4 nanostructures: controllable synthesis and enhanced electrochemical activity for oxygen evolution reaction

In this work, we demonstrated the enhanced oxygen evolution reaction (OER) activity of flower-shaped cobalt-nickel oxide (NiCo2O4) decorated with iridium-nickel bimetal as an electrode material. The samples were prepared by carefully depositing pre-synthesized IrNi nanoparticles on the surfaces of the NiCo2O4 nano-flowers. Compared with bare NiCo2O4, IrNi, and IrNi/Co3O4, the IrNi/NiCo2O4 exhibited significantly enhanced electrocatalytic activity in the OER, including a lower overpotential of 210 mV and a higher current density at an overpotential of 540 mV. We found that the IrNi/NiCo2O4 showed more efficient electron transport behavior and reduced polarization because of its bimetal IrNi modification by analyzing its Tafel slope and turnover frequency. Furthermore, the electrocatalytic mechanism of IrNi/NiCo2O4 in the OER was studied, and it was found that the combined active sites of the composite effectively improved the rate determining step. The synergic effect of the bimetal and metal oxide plays an important role in this reaction, enhancing the transmission efficiency of electrons and providing more active sites for the OER. The results reveal that IrNi/NiCo2O4 is an excellent electrocatalyst for OER.