Nanostructured Nickel Cobaltite Antispinel as Bifunctional Electrocatalyst for Overall Water Splitting

One major goal in the field of catalysis is to develop efficient, low-cost, and stable catalysts to replace noble-metal-based materials. Herein, we for the first time present the nickel cobaltite (NiCo2O4) of nanosheets morphology (NCO-NSs) and nanowires morphology (NCO-NWs) as an efficient electrocatalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution, affording a current density of 10 mA cm(-2) at low overpotential of 170 mV for the HER and 230 mV for the OER, respectively. With the aid of DFT calculation, we have evaluated their special catalytic activities by focusing on the position of d-band centers and adsorption energy of intermediates (H-2*, H*, H2O*, OH*, O*, OOH*, and O-2*) on catalyst surface. The result reveals that the rate determining-step for HER and OER is H* and O* adsorption, respectively, with the Ni-Td(3+) (Ni3+ occupied at the tetrahedral site) being the active site for water splitting. A highly efficient two-electrode electrolyzer based on NCO-NSs parallel to NCO-NWs configuration is designed and tested for long-term stability evolution. Furthermore, a NCO-NSs parallel to NCO-NWs based alkaline electrolyzer can be approach 15 mA cm(-2) at 1.65 V, superior to that of Pt parallel to IrO2 couple, along with strong stability.