Hierarchical Nanoboxes Composed of Co S -MoS 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 Co S -MoS hierarchical nanoboxes (HNBs) as efficient catalysts for the hydrogen evolution reaction (HER) is reported. The surface of the hollow cubic structure was organized by CoMoS nanosheets formed through the reaction of MoS and Co released from the cobalt zeolite imidazole framework (ZIF-67) templates under reflux in a mixture of water/ethanol. The formation process for the CoMoS HNB structures was characterized by TEM images recorded at various reaction temperatures. The amorphous CoMoS HNBs were converted through sequential heat treatments into CoS -MoS and Co S -MoS HNBs. Owing to their unique chemical compositions and structural features, Co S -MoS HNBs have a high specific surface area (124.6 m  g ) and superior electrocatalytic performances for the HER. The Co S -MoS HNBs exhibit a low overpotential (η ) of 106 mV, a low Tafel slope of 51.8 mV dec , and long-term stability in an acidic medium. The electrocatalytic activity of Co S -MoS HNBs is superior to that of recently reported values, and these HNBs prove to be promising candidates for the HER.