Superior Oxygen Evolution Reaction Performance of Co3O4/NiCo2O4/Ni foam Composite with Hierarchical Structure

In this work, ZIF-67 is self-grown on the NiCo layered double hydroxide (NiCo-LDH) nanosheets-modified Ni foam (NF) surface. Its derivative, the hierarchically structured Co3O4/NiCo2O4/Ni foam (CO/NCO/NF) composite, is successfully fabricated by the oxidation of ZIF-67/NiCo-LDH/ NF, which exhibits excellent electrocatalytic performance. When assessed as an electrode for oxygen evolution reaction (OER), the CO/NCO/NF electrode shows low overpotentials of 320 and 407 mV at 10 and 50 mA cm−2, respectively, in 0.1 M KOH aqueous electrolyte and an excellent long-term electrochemical durability with 88% current preservation during a 60 h test. It is also found that the OER activities of CO/NCO/NF electrode are superior to those of NCO/NF and CO/NF electrodes, demonstrating that the strong interaction of the interconnected interface of Co3O4 nanocages (CO NCs) and NiCo2O4 nanosheets (NCO NSs) is advantageous to increase the number of Co3+, improve conductivity, enhance structural stability, facilitate electronic transfer, and reduce reversible ion accumulation at the interface. In addition, the hierarchical architecture of the composite is binder-free and good for enhancing mass transport, boosting the dissipation of gases, as well as exposing catalytic active sites in the process of water electrolysis.