Mosaic-Structured Cobalt Nickel Thiophosphate Nanosheets Incorporated N-doped Carbon for Efficient and Stable Electrocatalytic Water Splitting

Engineering the nanostructures and compositions of 2D layered metal thiophosphates (MTPs) is significant for extending their applications. Here, a scalable and flexible strategy is presented to prepare single crystalline CoNiPS3 incorporated with N-doped carbon (CoNiPS3/C) nanosheets (approximate to 16 nm thickness), which can be further processed into the mosaic-structured CoNiPS3/C nanosheets (approximate to 6 nm thickness) composed of randomly distributed crystalline nanodomains (approximate to 15 nm diameter) and disordered boundaries (denoted as mosaic CoNiPS3/C nanosheets), and further into separated CoNiPS3/C nanodots (approximate to 4 nm diameter). The initial CoNiPS3/C nanosheeets are prepared by using Co-Ni Prussian-blue analogue nanoplates as templating precursors. As compared to the initial CoNiPS3/C nanosheets and nanodots, the mosaic CoNiPS3/C nanosheets exhibit plenty of active edge sites, retained crystallinity, and good structural stability. Synergistically, density functional theory calculations reveal that the bimetallic composition results in higher intrinsic activity, better conductivity, and lower kinetic energy barriers for bifunctional oxygen/hydrogen evolution reactions. More importantly, a water-splitting electrolyzer constructed using the mosaic CoNiPS3/C nanosheets as both cathode and anode achieves 30 mA cm(-2) at 1.62 V, which is better than the initial CoNiPS3/C nanosheets (1.69 V) and is comparable to the discreted nanodots (1.58 V). Besides, the mosaic CoNiPS3/C nanosheets show much better electrocatalytic stability than nanodots.