Catalytic Activity in Lithium-Treated Core-Shell MoO_x/MoS₂ Nanowires

Significant interest has grown in the development of earth-abundant and efficient catalytic materials for hydrogen generation. Layered transition metal dichalcogenides present opportunities for efficient electrocatalytic systems. Here, we report the modification of 1D MoO_x/MoS₂ core-shell nanostructures by lithium intercalation and the corresponding changes in morphology, structure, and mechanism of H₂ evolution. The 1D nanowires exhibit significant improvement in H₂ evolution properties after lithiation, reducing the hydrogen evolution reaction (HER) onset potential by ∼50 mV and increasing the generated current density by ∼600%. The high electrochemical activity in the nanowires results from disruption of MoS₂ layers in the outer shell, leading to increased activity and concentration of defect sites. This is in contrast to the typical mechanism of improved catalysis following lithium exfoliation, i.e., crystal phase transformation. These structural changes are verified by a combination of Raman and X-ray photoelectron spectroscopy (XPS).