Improved catalytic activity of Mo 1-x W x Se 2 alloy nanoflowers promotes efficient hydrogen evolution reaction in both acidic and alkaline aqueous solutions.

Layered transition metal dichalcogenides are noble-metal free electrocatalysts for the hydrogen evolution reaction (HER). Instead of using the common hydrothermal synthesis, which requires high pressure and temperature, herein a relatively simple and controlled colloidal synthesis was used to produce an alloy of Mo1-x Wx Se2 with nanoflower morphology as a model system for the electrocatalysis of hydrogen evolution in both acidic and alkaline environments. The results show that Mo1-x Wx Se2 alloys exhibit better catalytic activity in both acidic and alkaline solutions with low overpotentials compared to pure MoSe2 and WSe2 . Moreover, the electrode kinetics was studied using electrochemical impedance spectroscopy (EIS) and the results indicate that the alloys exhibit improved catalytic activity with low Tafel slopes, making them appealing for HER in either environment. Additionally, when MoSe2 nanoflowers (NFs) are prepared by using different metal salts and chalcogenide precursors, changes in the HER catalytic activity were observed, despite the morphology and crystal structure similarities. This finding suggests that different results reported in the literature could originate from different synthetic methods of the TMD, emphasizing that a better understanding of the relationship between the synthetic route and the catalytic performance is still lacking.