Engineering Rich Active Sites and Efficient Water Dissociation for Ni-Doped MoS₂/CoS₂ Hierarchical Structures toward...

Besides improving charge transfer, there are two key factors, such as increasing active sites and promoting water dissociation, to be deeply investigated to realize high-performance MoS₂-based electrocatalysts in alkaline hydrogen evolution reaction (HER). Herein, we have demonstrated the synergistic engineering to realize rich unsaturated sulfur atoms and activated O-H bonds toward the water for Ni-doped MoS₂/CoS₂ hierarchical structures by an approach to Ni doping coupled with in situ sulfurizing for excellent alkaline HER. In this work, the Ni-doped atoms are evolved into Ni(OH)₂ during alkaline HER. Interestingly, the extra unsaturated sulfur atoms will be modulated into MoS₂ nanosheets by breaking Ni-S bonds during the formation of Ni(OH)₂. On the other hand, the higher the mass of the Ni precursor (m_Ni) for the fabrication of our samples, the more Ni(OH)₂ is evolved, indicating a stronger ability for water dissociation of our samples during alkaline HER. Our results further reveal that regulating m_Ni is crucial to the HER activity of the as-synthesized samples. By regulating m_Ni to 0.300 g, a balance between increasing active sites and promoting water dissociation is achieved for the Ni-doped MoS₂/CoS₂ samples to boost alkaline HER. Consequently, the optimal samples present the highest HER activity among all counterparts, accompanied by reliable long-term stability. This work will promise important applications in the field of electrocatalytic hydrogen evolution in alkaline environments.