Unraveling the Tailored Exfoliation Mechanism and Electrochemical Behavior of α-NiCo Hydroxide Nanoplates for Water-Splitting Catalysis

The chemical exfoliation of layered metal hydroxides (LMHs) is a cutting-edge technology to obtain unilaminar and few-layer LMH nanosheets with positive charges and an ultrathin thickness, which widely serve as building blocks for functional composites in emerging fields. However, the preparation of high-quality monolayers with a large lateral dimension and regular morphology and the investigation of the exfoliation mechanism remain formidable challenges. Herein, uniform hexagonal NiCo LMH nanosheets were prepared by directly delaminating the well-crystallized α-type NiCo LMH nanoplate precursor in formamide with the assistance of mild heating. A plausible exfoliation mechanism suggests that formamide diffuses rapidly with the assistance of heating, facilitating expansion of the interlayer spacing of the LMH bulk. Subsequently, the precursor undergoes a gradual delamination process to form uniform hexagonal monolayers, as the interlayer force diminishes. Moreover, the positively charged LMH nanosheets are utilized as nanoblocks to electrostatically adsorb anionic polystyrene sodium 4-sulfonate (PSS) or negatively charged reduced graphene oxide (rGO) via a layer-by-layer (LBL) self-assembly method. The constructed (NiCo LMH/PSS)n and (rGO/NiCo LMH)n multilayer heterostructure films are highly viable in electrochemical applications.