Improved catalytic activity of Mo_{1-: X}W_xSe₂ 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 Mo_1-xW_xSe₂ with nanoflower morphology as a model system for the electrocatalysis of hydrogen evolution in both acidic and alkaline environments. The results show that Mo_1-xW_xSe₂ 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.