Solution synthesis of core–shell Co9S8@MoS2catalystsElectronic supplementary information (ESI) available. See DOI: 10.1039/c6cy00311g

Core–shell Co9S8@MoS2unsupported catalysts have been prepared by a solution reaction in ethylene glycol. First, using a cobalt sulfide seed, amorphous core–shell CoS@MoSx(x= 3–4) was prepared. Then, after thermal treatment, 20–50 nm-sized particles were obtained, in which MoS2was crystallized at the exterior of the Co9S8core. The solids show high catalytic activity in hydrodesulphurization, with an exceptionally high thermal stability. Thus, the high catalytic activity was preserved even after thermal treatment at 750 °C. A symmetric synergy model has been proposed with the catalytic sites located at the interface between the cobalt sulfide crystallites and the stacks of MoS2slabs.