In-situ structure reconstitution of NiCoP for enhanced electrochemical water oxidation.

Gaining insight into the structure evolution of transition-metal phosphides during anodic oxidation is significant to understand their oxygen evolution reaction (OER) mechanism, and then design high-efficiency transition metal-based catalysts. Herein, NiCoP nanowires (NWs) vertically grown on Ni foam were adopted as the target to explore the in-situ morphology and chemical component reconstitution during the anodic oxidation. The major factors causing the transformation from NiCoP into the hierarchical NiCoP@CoNi(OOH) NWs are two competing reactions: the dissolution of NiCoP NWs and the oxidative re-deposition of dissolved Co and Ni ions, which is based primarily on the anodic bias applied on NiCoP NWs. The well balance of above competing reactions, and local pH on the surface of NiCoP NW modulated by the anodic oxidation can serve to control the anodic electrodeposition and rearrangement of metal ions on the surface of NiCoP NWs, and the immediate conversion into CoNi(OOH). Consequently, the regular hexagonal CoNi(OOH) nanosheets grew around NiCoP NWs. Benefiting from the active catalytic sites on the surface and the sufficient conductivity, the resultant NiCoP@CoNi(OOH) arrays also display good OER activity, in terms of the fast kinetics process, the high energy conversion efficiency, especially the excellent durability. The strategy of in-situ structure reconstitution by electrochemical reaction described here offers a reliable and valid way to construct the highly active systems for various electrocatalytic applications.