Construction of porous nanoscale NiO/NiCo2O4 heterostructure for highly enhanced electrocatalytic oxygen evolution activity.

A novel porous nanoscale NiO/NiCo 2 O 4 heterostructure with abundant interfaces is designed to enhance the performance of oxygen evolution reaction (OER). The NiO/NiCo 2 O 4 heterostructure exhibits superior OER activity with a low overpotential (264 mV @10 mA cm−2) and small Tafel slope (44.2 mV dec−1). It also showcases excellent electrochemical stability which can remain stable over 24 h at 100 mA cm−2. • Nanoscale NiO/NiCo 2 O 4 heterostructure is fabricated by two-stage calcination approach. • The electrocatalyst possesses abundant pores and heterostructure interfaces. • Porous nanostructure exposes more active sites. • Ni3+ species endow the catalyst with superior intrinsic activity. • Interfaces promote the chemisorption of oxygen-containing intermediates. Developing highly active and inexpensive electrocatalysts for oxygen evolution reaction (OER) is critical to large-scale applications of electrochemical water splitting. In the present work, a novel porous NiO/NiCo 2 O 4 heterostructure is constructed by two-stage calcination of nickel-cobalt bimetallic hydroxide precursors prepared using a microwave-assisted hydrothermal method, in which abundant interfaces are constituted. The NiO phase stabilized in NiCo 2 O 4 matrix is the nanometer scale (ca. 13 nm). The porous nanoscale NiO/NiCo 2 O 4 heterostructure shows a 10 mA cm−2 current density under the overpotential of 264 mV which outperforms the noble catalyst RuO 2. It is demonstrated that the highly active Ni3+ species generated by the oxidation of nanometer scale NiO surface are responsible for enhanced OER. Additionally, DFT calculations certify that the heterostructure interfaces promote the chemisorption of OH intermediates. This strategy of increasing the intrinsic activity and improving the chemisorption abilities for oxygen-containing intermediates by constructing nanoscale heterostructure electrocatalysts provides a feasible method to accelerate the reaction rate of OER. [ABSTRACT FROM AUTHOR]