Polyoxometalate precursors for precisely controlled synthesis of bimetallic sulfide heterostructure through nucleation-doping competition

Molybdenum disulfide (MoS2)-based bimetallic sulfides have drawn increasing research attention because of their unique structures and properties. Herein, a one-pot hydrothermal synthesis method is proposed to grow a series of bimetallic sulfides on carbon cloth (M-Mo-S/CC, M = Co, Ni, Fe) using Anderson-type polyoxometalates (POMs) as bimetallic sources for the first time. An ideal model of M-Mo-S/CC was used to study the growth process through the nucleation-doping competition mechanism. It is proved for the first time that M-Mo-S/CC possess certain compositions of bimetallic sulfides rather than metal doped MoS2 structures because the nucleation reaction is predominant in the nucleation-doping competition. Moreover, the nucleation rates of different metals can be compared to study the different morphologies of M-Mo-S/CC because Anderson-type POMs have fixed bimetal proportions and precise structures. Co-Mo-S and Ni-Mo-S show spherical heterostructures with CoS2 or NiS mainly inside and interconnected MoS2 nanosheets outside, while Fe-Mo-S exhibits uniform nanosheet morphology without stacking. As electrodes for alkaline water electrolysis, M-Mo-S/CC with different compositions and morphologies exhibit a variety of activities. Particularly, among the M-Mo-S/CC samples, Co-Mo-S/CC achieves the best performance for hydrogen evolution reaction, oxygen evolution reaction and overall water splitting. This study presents a facile strategy of using POMs as bimetallic precursors for studying the growth mechanism as well as the water electrolysis performances of MoS2-based bimetallic sulfides.