Facile Synthesis of Heterostructured Nickel/Nickel Oxide Wrapped Carbon Fiber: Flexible Bifunctional Gas-Evolving Electrode for Highly Efficient Overall Water Splitting

Electrochemical water-splitting provides an effective strategy to convert electrical energy into renewable energy resource. In this work, we report a bifunctional gas-evolving fibrous electrode based on nonprecious heterostructured Ni@NiO wrapped carbon fiber (CF) for overall water splitting reaction. The proposed Ni@NiO wrapped CF (CF@Ni@NiO) was fabricated through a simple and controllable electrodeposition and subsequent low-temperature calcination procedure, which can easily be scaled up for practical use. Benefitting from the exposed heterojunction-like Ni@NiO nanointerfaces and the formation of Ni (III) species, the resultant CF@Ni@ NiO electrode exhibits excellent catalytic activity, favorable kinetics, as well as strong durability toward both cathodic hydrogen evolution reactions (HER) and anodic oxygen evolution reactions (OER) in alkaline electrolyte, with an overall water-splitting current of 20 mA cm(-2) at 1.73 V (iR uncorrected), which outperforms that of other reported nonprecious electrocatalysts. Moreover, owing to their intrinsic mechanical flexibility, these fibrous gas-evolving electrodes can be readily woven into textile structures for practical applications. The simple, low-cost, and scalable fabrication process of heterostructured materials modified fibrous electrode, coupled with recent progress in nonprecious electrocatalysts for both HER and OER, offers the possibilities to systematically study the dependence of catalytic performance on the structural parameters of the electrocatalysts, which also open new horizon for the development of next-generation flexible water-splitting devices.