Electrochemical activation-induced surface-reconstruction of NiOx microbelt superstructure of core-shell nanoparticles for superior durability electrocatalysis.

The tailoring of intrinsic electronic structures and extrinsic hierarchical morphologies is widely recognized as a promising strategy to enhance the oxygen evolution reaction (OER) performance of electrocatalysts. It is generally accepted that the surface of the transition metal-based electrocatalyst exposed to the alkaline electrolyte is highly oxidized and reconstructed, forming an amorphous layer during the electrochemical process. This amorphous active phase is favorable for OER due to its abundant dangling bonds, vacancies and defects, which is tricky to be rationally prepared by conventional methods. Herein, a facile access to crystalline / amorphous NiOx microbelt superstructure of core-shell nanoparticles is presented, which is assembled of crystalline NiO nanoparticles coated with amorphous Ni3+/Ni2+ oxide layer. Electrochemical activation induces the in-situ surface reconstruction of the NiOx microbelt superstructure, resulting in a thicker outer amorphous Ni3+/Ni2+ layer further facilitating OER. Owing to the optimization of the in-situ surface reconstruction, the NiOx microbelt superstructure with crystalline / amorphous dual phases exhibited both high electrocatalytic activity and superior durability for OER, with the original microbelt superstructure retained after 50000 s I-t test.