Bimetallic Nickel Cobalt Sulfide as Efficient Electrocatalyst for Zn-Air Battery and Water Splitting

HighlightsBimetallic nickel cobalt sulfide (Ni,Co)S-2 nanosheet arrays were demonstrated as a multifunctional catalyst for OER, HER, and ORR.First principle calculations were performed to probe the rate-limiting step, which involves the formation of *OOH from HO- on the (Ni,Co)S-2 surface.A water-splitting system was designed with the (Ni,Co)S-2 serving as both cathode and anode, and a Zn-air battery cathode electrocatalyst. AbstractThe development of efficient earth-abundant electrocatalysts for oxygen reduction, oxygen evolution, and hydrogen evolution reactions (ORR, OER, and HER) is important for future energy conversion and energy storage devices, for which both rechargeable Zn-air batteries and water splitting have raised great expectations. Herein, we report a single-phase bimetallic nickel cobalt sulfide ((Ni,Co)S-2) as an efficient electrocatalyst for both OER and ORR. Owing to the synergistic combination of Ni and Co, the (Ni,Co)S-2 exhibits superior electrocatalytic performance for ORR, OER, and HER in an alkaline electrolyte, and the first principle calculation results indicate that the reaction of an adsorbed O atom with a H2O molecule to form a *OOH is the potential limiting step in the OER. Importantly, it could be utilized as an advanced air electrode material in Zn-air batteries, which shows an enhanced charge-discharge performance (charging voltage of 1.71V and discharge voltage of 1.26V at 2mAcm(-2)), large specific capacity (842mAhg-1 at 5mAcm(-2)), and excellent cycling stability (480h). Interestingly, the (Ni,Co)S-2-based Zn-air battery can efficiently power an electrochemical water-splitting unit with (Ni,Co)S-2 serving as both the electrodes. This reveals that the prepared (Ni,Co)S-2 has promising applications in future energy conversion and energy storage devices.