Hierarchically designed CoMo marigold flower-like 3D nano-heterostructure as an efficient electrocatalyst for oxygen and hydrogen evolution reactions

Rational design of high performance bifunctional non-precious electrocatalysts is essential for the development of renewable energy conversion and storage technologies. Herein, we report a simple and effective hydrothermal method to synthesize a three-dimensional (3D) marigold-like cobalt-molybdenum layered double hydroxide (CoMo-LDH) flowers assembled by two-dimensional (2D) ultrathin nanosheets. Especially, the main difference with the previous reports of 2D CoMo-LDH nanosheets is the fact that the present 3D CoMo-LDH catalyst with high dense feature provide abundant active sites for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline solution. Among the synthesized various Co/Mo ratios of LDHs (Co1Mo4, Co2Mo3, Co3Mo2, and Co4Mo1), the Co3Mo2-LDH exhibits the superior OER activity, delivering small overpotential of 266 mV at 10 mA cm−2 with low Tafel slope of 49 mV dec−1. Furthermore, Co3Mo2-LDH also show remarkable HER activity offering low overpotential of 325 mV at 100 mA cm−2, which outperforms the commercial Pt/C. Co3Mo2-LDH catalyst also demonstrates the excellent stability over 12 h. The enhanced OER and HER activity of Co3Mo2-LDH can be attributed to its high electrochemical surface area, inherent layered 2D structure, synergistic effects of Co and Mo metal atoms, and compositional merits.