Hierarchical Nanoboxes Composed of Co9S8-MoS2 Nanosheets as Efficient Electrocatalysts for the Hydrogen Evolution Reaction

The development of hydrogen evolution catalysts based on nonprecious metals is essential for the practical application of water-splitting devices. Herein, the synthesis of Co9S8-MoS2 hierarchical nanoboxes (HNBs) as efficient catalysts for the hydrogen evolution reaction (HER) is reported. The surface of the hollow cubic structure was organized by CoMoS4 nanosheets formed through the reaction of MoS42- and Co2+ released from the cobalt zeolite imidazole framework (ZIF-67) templates under reflux in a mixture of water/ethanol. The formation process for the CoMoS4 HNB structures was characterized by TEM images recorded at various reaction temperatures. The amorphous CoMoS4 HNBs were converted through sequential heat treatments into CoSx-MoS2 and Co9S8-MoS2 HNBs. Owing to their unique chemical compositions and structural features, Co9S8-MoS2 HNBs have a high specific surface area (124.6m(2)g(-1)) and superior electrocatalytic performances for the HER. The Co9S8-MoS2 HNBs exhibit a low overpotential ((10)) of 106mV, a low Tafel slope of 51.8mVdec(-1), and long-term stability in an acidic medium. The electrocatalytic activity of Co9S8-MoS2 HNBs is superior to that of recently reported values, and these HNBs prove to be promising candidates for the HER.