Superconfinement Engineering of Hetero-Nanoparticles in Ultrathin Carbon Nanosheets Enables Highly-Efficient Water Splitting.

Developing highly active and robust bifunctional electrocatalysts for overall water splitting is of great significance for the production of green hydrogen energy. Herein, heterostructured CoP/NiCoP nanoparticles that are encapsulated one-to-one in nano caves of soda-biscuit-like ultrathin carbon nanosheets (CoP/NiCoP/CMS) are prepared, using melamine-formaldehyde sponge (MS) that grew Co/NiCo hydroxides as precursor and phytic acid (PA) as phosphorus source. Especially, the PA-induced blowing behavior during pyrolysis not only transforms the 3D networks of MS into 2D ultrathin carbon nanosheets of CMS, but also achieves the uniform one-to-one superconfinement of hetero-nanoparticles within both the intralayer nanocaves and interlayer spaces of the carbon nanosheets. Benefit from the superconfinement and interface engineering, CoP/NiCoP/CMS shows low overpotentials of 247 and 124 mV at 10 mA cm-2, as well as good stabilities toward both oxygen and hydrogen evolution reactions, respectively. Moreover, CoP/NiCoP/CMS//CoP/NiCoP/CMS electrolyzer only requires 1.56 V to achieve 10 mA cm-2. Experimental and theoretical results demonstrate that heterojunction interfaces can well regulate the electronic structure and enhance the intrinsic activity of CoP/NiCoP/CMS, meanwhile, soda-biscuit-like architecture guarantees the compatibility of high activity and good stability. This work proposes a novel and universal strategy for designing advanced electrocatalysts for efficient overall water splitting.