The Role of Additives in Suppressing the Degradation of Liquid‐Exfoliated WS₂ Monolayers

Abstract

Group VI transition metal dichalcogenides (TMDs) are considered to be chemically widely inert, but recent reports point toward an oxidation of monolayered sheets in ambient conditions, due to defects. To date, the degradation of monolayered TMDs is only studied on individual, substrate‐supported nanosheets with varying defect type and concentration, strain, and in an inhomogeneous environment. Here, degradation kinetics of WS2 nanosheet ensembles in the liquid phase are investigated through photoluminescence measurements, which selectively probe the monolayers. Monolayer‐enriched WS2 dispersions are produced with varying lateral sizes in the two common surfactant stabilizers sodium cholate (SC) and sodium dodecyl sulfate (SDS). Well‐defined degradation kinetics are observed, which enable the determination of activation energies of the degradation and decouple photoinduced and thermal degradation. The thermal degradation is slower than the photoinduced degradation and requires higher activation energy. Using SC as surfactant, it is sufficiently suppressed. The photoinduced degradation can be widely prevented through chemical passivation achieved through the addition of cysteine which, on the one hand, coordinates to defects on the nanosheets and, on the other hand, stabilizes oxides on the surface, which shield the nanosheets from further degradation.

Sonication-assisted liquid exfoliation and size-dependent properties of magnetic two-dimensional α-RuCl3

“…t 1/2 (20 [25,67], we note that the half-lives are relatively long. This implies that, while the degradation of the material is observed at moderate temperatures already, the available timeframe until a significant portion of the material is affected from environmental impacts is reasonable for all material fractions studied within the scope of this work (t 1/2 > 30 days), and is in agreement with previously reported results on aging effects on micromechanically-cleaved RuCl 3 nanosheets [4].…”

Exfoliablity, magnetism, energy storage and stability of metal thiophosphate nanosheets made in liquid medium

“…The metrics and timescales for the decomposition do not only provide information about liquid-exfoliated M 2 P 2 S 6 nanosheets, but the procedure can be transferred to other material systems, which demonstrates a universally applicable set of experiments to assess size-dependent properties and environmental material stability. We consider these results important as they enable comparison of fundamental material properties for compositionally and structurally different material systems and for different chemical environments [13,38,41,113].…”

Protective Nanosheet Coatings for Thiophosphate‐Based All‐Solid‐State Batteries

“…From the electrochemical testing, WS 2 -NCM was found to deliver the highest specific capacities (note: similar stabilization was achieved with the niobate-type nanosheets in SSB cells). Since WS 2 is reactive toward ambient oxygen, [64][65][66][67] it is necessary to characterize the actual coating species given that the nanosheets may transform into some oxidized state during deposition and/or post-deposition anneal.…”