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In this work, we developed an evaporation crystallization method combined with a hydrogen thermal reduction method to construct a MoO2/MoS2 heterojunction on carbon nanotubes (denoted as MoO2/MoS2@CNT) for hydrogen evolution. In the HER process, the resultant MoO2/MoS2@CNT exhibited excellent catalytic activity, which featured a small overpotential of 158 mV at a current density of 10 mA cm−2 along with a Tafel slope of 70 mV dec−1 as well as excellent stability in 0.5 M H2SO4. Experimental findings and theoretical calculations show that the excellent electrocatalytic performance is mainly due to the strong interaction between MoO2 and MoS2, which can help to effectively optimize the electronic structure, lower the catalytic energy barrier, and thereby enhance the HER activity. This work provides an effective strategy for constructing a heterojunction to regulate the electron structure, which will generate more inspiration for designing efficient electrocatalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MoSe 2 particle and C@MoSe 2 core-shell composite electrocatalysts were successfully prepared by a simple sol-gel approach. • The C@MoSe 2 core-shell composites show a higher HER activity than MoSe 2 particles. • The good performance can be mainly attributes to the improved electric conductivity. • This work provides a new method to synthesize MoSe 2 and C@MoSe 2 composite without reducing agent. Abstract In this work, we show the successful synthesis of MoSe 2 particle and C@MoSe 2 core-shell composite electrocatalysts by a simple sol-gel approach. The carbon sphere shells can effectively prevent the aggregation of MoSe 2 nanosheets and greatly improve the conductivity of the hybrid structure, making the C@MoSe 2 has good HER activity with an onset overpotential of ∼−170 mV and a Tafel slope of ∼72 mV dec−1. This work paves a new way to synthesize MoSe 2 -based electrocatalyst and can be extended as a general strategy to prepare other two-dimensional materials, such as WSe 2 and VSe 2. [ABSTRACT FROM AUTHOR]

Here we report a highly active catalyst for hydrogen evolution reaction (HER) that is constructed by in situ growth of MoS 2 on the surface of MoSe 2 nanosheets (MoSe 2 @MoS 2 ). Compared with either single MoS 2 or MoSe 2 , the MoSe 2 @MoS 2 electrocatalyst exhibits better electrocatalytic activity with a small Tafel slope (60 mV dec −1 ) and a low onset overpotential (−161 mV). The good HER activity is attributed to its core-shell nanostructure, which can not only efficaciously suppress the aggregation of MoS 2 nanosheets, but also generate more active sites and produce a synergistic effect of the two components in the HER. This approach provides an effective pathway to improve HER activity of MoS 2 or MoSe 2 catalysts and can be used for other two-dimensional semiconductor electrocatalyst. [ABSTRACT FROM AUTHOR]

Structure and morphology play a crucial role in improving the performance of catalysts. In this work, we prepared core-shell structured CoS 2 @MoS 2 nanoparticles by a two-step hydrothermal method. The unique electrochemical properties of the core-shell CoS 2 @MoS 2 nanoparticles with a narrow size distribution centered at 20–30 nm were demonstrated. An excitation-dependent photoluminescence emission was observed for the core-shell CoS 2 @MoS 2 nanoparticles. These core-shell CoS 2 @MoS 2 nanoparticles showed an excellent catalytic activity towards hydrogen evolution reaction (HER), indicated by the onset potential of 190 mV (vs. RHE), the overpotential of 276 mV at a current density of 10 mA cm−2 and the Tafel slope of 60 mV·dec−1. Therefore, the developed core-shell CoS 2 @MoS 2 nanoparticles can be applied for HER for their excellent catalytic activities. 1.We prepared core-shell structured CoS 2 @MoS 2 nanoparticles by a two-step hydrothermal method. 2. The structure and morphology are crucial factors in the performance of HER catalyst. 3. Core-shell CoS 2 @MoS 2 nanoparticles exhibits high HER activity and low onset overpotential. [ABSTRACT FROM AUTHOR]