Mesoporous nanostructures of NiCo-LDH/ZnCo2O4 as an efficient electrocatalyst for oxygen evolution reaction.

Increasing energy demands for pollution-free and renewable energy technologies have stimulated intense research on the development of inexpensive, highly efficient, and stable non-noble metal electrocatalysts for oxygen evolution reaction (OER). In this study, a superior OER performance was achieved using a tri-metallic (Zn, Co, Ni) high-performance electrocatalyst. We successfully fabricated a peony-flower-like hierarchical ZnCo2O4 through an additive-free hydrothermal reaction followed by heat treatment. Then NiCo-LDH (layered double hydroxides) nano-flakes was electrodeposited on the ZnCo2O4/GCE surface to prepare NiCo-LDH/ZnCo2O4/GCE which was used as electrode for OER. The structure and morphology of the catalysts were characterized by several techniques including Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping and Brunauer-Emmett-Teller method. The NiCo-LDH/ZnCo2O4 catalyst provided high catalytic activity toward OER under alkaline condition (1.0 M KOH) with a low overpotential of 260 mV to drive the benchmark current density of 10 mA cm-2 and Tafel slope of 62 mV dec-1, as well as long-term stability and high turnover frequency of 0.0641 s-1 at overpotential of 340 mV. The NiCo-LDH/ZnCo2O4 catalyst was found to perform significantly better than NiCo-LDH, ZnCo2O4, NiCo-LDH/Co3O4, Co3O4, and commercial RuO2 catalysts. The outstanding OER performance of NiCo-LDH/ZnCo2O4 catalyst, which may be attributed to the large specific surface area, accelerated mass and electron transport, and synergistic effect of multiple hybrid materials, makes it a promising catalyst for OER.