Three-dimensional flower-like NiCo₂O₄/CNT for efficient catalysis of the oxygen evolution reaction

The oxygen evolution reaction (OER) is an important reaction especially in water splitting and metal-air batteries. Highly efficient non-noble metal based electrocatalysts are urgently required to be developed and to replace the commercial Ru/Ir based oxide. Herein, we report the three-dimensional hierarchical NiCo₂O₄/CNT-150 composite with high activity for the OER that was synthesized via a hydrothermal reaction and subsequent annealing. Compared with CNTs, commercial RuO₂ catalysts, NiCo₂O₄/CNT, NiCo₂O₄/CNT-250, and NiCo₂O₄/CNT-150 exhibit enhanced electrocatalytic performance with a lower onset overpotential of 300 mV and the corresponding Tafel slope of 129 mV per decade. The flower-like NiCo₂O₄/CNT-150 shows an excellent catalysis performance with higher current density than the commercial RuO₂ catalyst. Moreover, the NiCo₂O₄/CNT-150 demonstrates the excellent long-term durability in 0.1 mol L^-1 KOH for the OER. The significant catalytic performances are ascribed to the excellent conductivity of CNTs and the high specific surface area of the three dimensional flower-like NiCo₂O₄.