Heterostructured ZnCo2O4-CoOOH nanosheets on Ni foam for a high performance bifunctional alkaline water splitting catalyst.

ABSTRACT

It is of utmost importance to explore bifunctional electrocatalysts for water splitting. Herein, unique ZnCo2O4-CoOOH heterostructured ultrathin nanosheets on Ni foam are reported that combines a two-step hydrothermal method. This catalyst exhibits excellent catalytic performances to achieve a current density of 10 mA cm-2 with an ultralow overpotential of 115 mV for HER, attaining an overpotential of 238 mV at 20 mA cm-2 for OER. Remarkably, ZnCo2O4-CoOOH/Ni shows a voltage of 1.494 V to drive a current density of 10 mA cm-2. Such performances are due to the inter-penetrative pores present in the ultrathin nanosheets that provide large surface areas and expose massive active sites to enhance activities. In addition, the unique nanosheet structure and the 3D Ni foam substrate possess large specific surface areas, which can facilitate mass diffusion. This excellent performance is ascribed to the ZnCo2O4-CoOOH heterostructure that manipulates strong synergy to improve the electrochemical activity. This study offers new insight on an innovative approach for the exploitation of effective bifunctional electrocatalysts with a heterostructure.