Molybdenum disulfide (MoS2) with metallic 1T phase is perceived as the possible alternative to benchmark Pt in the hydrogen evolution reaction (HER). The dominance prevailing in the density of active sites, electrical conductivity, and hydrophilicity of 1T phase improves HER kinetics. In the construction of MoS2, 2H is the stable phase due to its thermodynamic stability over the 1T phase. On other hand, the Li+ ion intercalation/exfoliation technique converts 2H to a metastable 1T phase. Pyrophoric Li+ ion, an organic solvent, suffers from sluggish intercalation/exfoliation kinetics and is still a setback in attaining conversion. Based on these investigations, herein, for the very first time, such a phase conversion was reached by soaking the 2H-MoS2 in only polar solvents. Among the various polar solvents, extended phase conversion (70.1%) was attained in N,N-dimethylformamide (DMF) when 2H-MoS2 was immersed for 90 days, i.e., DMF-90D catalyst. Upon the prolonged immersion, the electrostatic forces between solvent and 2H-MoS2 occur, and the van der Waals forces between the layers of MoS2 are diminished. Under such conditions, solvent molecules intercalate into MoS2 and induce phase conversion from the 2H to 1T phase. The density functional theory (DFT) study further verified that only the electrostatic interactions are present between the solvent and MoS2 and that no charge transfer emerged. In acidic HER, the DMF-90D catalyst to secure 10 mA cm–2 required 263 mV with a lower Tafel slope value (59 mV/dec). This facile and greener approach can be further extended to other impressive 2D materials in the future.

Molybdenum disulfide

Exfoliation joint

10.1021/acsaem.3c02487

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Two-stage classifier for face recognition using HOG features

Materials Today Proceedings (2021)

M. Chandrakala P. Durga Devi

Three-dimensional face recognition

10.1016/j.matpr.2021.04.114

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