Unraveling the Role of Lithium in Enhancing the Hydrogen Evolution Activity of MoS₂: Intercalation versus Adsorption

Abstract

Molybdenum disulfide (MoS2) is a highly promising catalyst for the hydrogen evolution reaction (HER) to realize large-scale artificial photosynthesis. The metallic 1T′-MoS2 phase, which is stabilized via the adsorption or intercalation of small molecules or cations such as Li, shows exceptionally high HER activity, comparable to that of noble metals, but the effect of cation adsorption on HER performance has not yet been resolved. Here we investigate in detail the effect of Li adsorption and intercalation on the proton reduction properties of MoS2. By combining spectroscopy methods (infrared of adsorbed NO, 7Li solid-state nuclear magnetic resonance, and X-ray photoemission and absorption) with catalytic activity measurements and theoretical modeling, we infer that the enhanced HER performance of LixMoS2 is predominantly due to the catalytic promotion of edge sites by Li.

The Origin of High Activity of Amorphous MoS2 in the Hydrogen Evolution Reaction

“…Nonetheless, the disorder in amorphous MoS 2 reported in this work is consistent with earlier reports . It is worth noting that even though the HER activity of 1T‐MoS 2 decreases gradually (Figure d), the corresponding overpotential is still much lower than that of 2H‐MoS 2 , which we have recently attributed to the presence of remaining Li adsorbed on the 1T‐MoS 2 even after loss of intercalated Li . Inductively coupled plasma optical emission spectroscopy (ICP‐OES) analysis of MoS 2 films after stability tests confirms the presence of adsorbed Li on 1T‐MoS 2 (Table S4), and the adsorption of Li on MoS 2 was observed to promote the activity of MoS 2 ‐catalyzed hydrogen evolution reaction in our recent work …”

The Characterisation of Electrodeposited MoS2 Thin Films on a Foam-Based Electrode for Hydrogen Evolution

“…Different methods to improve the catalytic activity of transition metal dichalcogenides such as MoS 2 have been proposed. Doping with lithium, transition metals or even anionic nitrogen has been shown to have various effects on MoS 2 , including an enhanced catalytic activity when compared with the unmodified material [28][29][30][31]. Some methods focus on nanostructurisation to reveal a maximum amount of active sites [32], while others combine MoS 2 with electro-or photoactive materials to form functional composites with combined properties [33].…”

Effect of Ni Doping on the MoS2 Structure and Its Hydrogen Evolution Activity in Acid and Alkaline Electrolytes

“…However, TMDCs have some critical issues, such as a limited electrical conductivity and restacking phenomena. Several strategies are currently tested to improve the HER activity of MoS 2 : doping with transition metals [21][22][23][24][25], anion substitution [26][27][28], preparation of composites [29][30][31], or materials with special morphologies [32,33]. Tsai et al screened the effect of 19 transition metals dopants on MoS 2 by DFT calculations [34].…”