Provoking Metallic 1T Phase Conversion of 2H-MoS₂ via an Effectual Solvothermal Route for Electrocatalytic Water Reduction in Acid

Abstract

Recently, the exploration of MoS 2 -based catalysts especially with a metallic 1T phase has gained immense attention due to their improvised electrocatalytic performance in hydrogen evolution reaction (HER). The dominance in electrical conductivity, hydrophilicity, and density of active sites with the metallic 1T phase over a semiconducting 2H phase is liable for their promoted catalytic performance. The direct formation of MoS 2 with an electrocatalytically active 1T phase is hard to attain and demands a proficient method since it is a metastable phase, whereas the 2H phase is a thermodynamically stable and predominantly formed phase in MoS 2 . On the other hand, in MoS 2 , the phase conversion from the thermodynamically stable 2H phase to the metastable 1T phase can be feasible with the Li + ion exfoliation technique. Although it is the foremost employed technique for the industrial-scale formation of 1T-MoS 2 at present, the tedious and sedate intercalation/exfoliation process and the usage of explosive Li metal are the prime drawbacks within it. To overcome these issues, in this report, we have proposed a new route for the facile conversion of the 2H phase to the metallic 1T phase in MoS 2 , which is a solvothermal agitation process with N,N-dimethylformamide (DMF) solvent, where the interlayer expansion due to the intercalation of DMF was observed, which assisted in the attainment of maximal (78.6%) conversion of the 1T phase. Then, the electrocatalytic performance of the prepared 1T-MoS 2 catalysts in HER was tested and they showed tremendous activity. To attain a current density of 10 mA cm −2 , it demanded 262 mV with a lower Tafel slope value of 53 mV/dec. This humble expedient technique can be valid to the other 2D materials for the facile conversion of the 2H phase to the electrochemically active 1T phase.

Exfoliation Procedure-Dependent Optical Properties of Solution Deposited MoS2 Films

“…Furthermore, a single distribution is sufficient to fit the Mo +4 peak indicating there is no residual 1T phase present after the reconversion process. Similar S/Mo has been reported for conventional CEPR where phase reconversion induces Mo-oxide species 79 . Fig.…”

Tailoring of 1T Phase-Domain MoS2 Active Sites with Bridging S22–/Apical S2– Phase-Selective Precursor Modulation for Enriched HER Kinetics

“…After the successful synthesis of 1T phase-domain MoS 2 from ATTM by the employment of various conditions like three different solvents (H 2 O, DMF, and EG) with/without reducing agents, XRD has been performed for all the samples to ensure the formation of MoS 2 . Then, the obtained results are depicted here with the comparison 2H–MoS 2 (from our previous study) and ICDD card no. 00-037-1492 in Figure a,b.…”

“…At present, transfiguration from semiconducting/stable 2H to metallic/metastable 1T phase via Li + ion exfoliation is the substantially employed approach for the industrial-scale synthesis of 1T-MoS 2 . ,, However, the employment of harmful organic solvents, pyrophoric Li + ion, request of inert condition, and the sluggish intercalation/exfoliation kinetics are the prime setbacks linked with this methodology. On the other hand, there are many discrete ways for the direct synthesis of 1T-MoS 2 , that is, strain-induced, , doping-induced, , pulse laser deposition, , hydrothermal/solvothermal, , template-driven, , and intercalated guest molecule-/ion-assisted approach. − In all these direct 1T phase formation approaches, the reaction parameters such as precursors, reaction time, temperature, and solvents play a pivotal role for phase enrichment. When considering the temperature and reaction time, 160–240 °C and 12–24 h are the comprehensively used ranges, respectively, decided by the activation energy of the precursors and the boiling point of the solvents used. , The relatively low temperature (≤200 °C) with an extended reaction time (up to 24 h) is the more appropriate circumstance for the formation of MoS 2 with elevated 1T phase selectivity.…”

“…In the case of solvents, water, ethanol, N , N -dimethylformamide (DMF), and ammonium hydroxide (NH 4 OH) are typically used for the formation of 1T-MoS 2 , where the solvent preference depends on the precursors/reagents. ,,, Besides, upon the synthesis, certain solvents or ions in the solvent are being intercalated and raise the interlayer spacing, thereby assisting to form the metallic1T phase. The polar solvents are more pertinent for that purpose as they are capable of compensating the diminished van der Waals forces that occurred by the upswing of interlayer spacing …”

Heterostructured Palladium–Nickel Sulfide on Plasma-Activated Nickel Foil for Robust Hydrogen Evolution

“…Hence, developing high-performance Pt-free electrocatalysts shows paramount significance. Currently, many works are reported to design high-performance catalysts based on non-noble metals, especially based on the engineered transition metal oxides (TMOs), phosphides (TMPs), dichalcogenides (TMDs), etc. Among them, TMD-based catalysts present high electrocatalytic activity due to their pronounced metallic features and heterointerfaces .…”