High‐Yield Electrochemical Production of Large‐Sized and Thinly Layered NiPS₃ Flakes for Overall Water Splitting

Abstract

Abstract Achieving large‐sized and thinly layered 2D metal phosphorus trichalcogenides with high quality and yield has been an urgent quest due to extraordinary physical/chemical characteristics for multiple applications. Nevertheless, current preparation methodologies suffer from uncontrolled thicknesses, uneven morphologies and area distributions, long processing times, and inferior quality. Here, a sonication‐free and fast (in minutes) electrochemical cathodic exfoliation approach is reported that can prepare large‐sized (typically ≈150 µm 2 ) and thinly layered (≈70% monolayer) NiPS 3 flakes with high crystallinity and pure phase structure with a yield ≈80%. During the electrochemical exfoliation process, the tetra‐ n ‐butylammonium salt with a large ionic diameter is decomposed into gaseous species after the intercalation and efficiently expands the tightly stratified bulk NiPS 3 crystals, as revealed by in situ and ex situ characterizations. Atomically thin NiPS 3 flakes can be obtained by slight manual shaking rather than sonication, which largely preserves in‐plane structural integrity with large size and minimum damage. The obtained high quality NiPS 3 offers a new and ideal model for overall water splitting due to its inherent fully exposed S and P atoms that are often the active sites for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Consequently, the bifunctional NiPS 3 exhibits outstanding performance for overall water splitting.