General Bottom-Up Colloidal Synthesis of Nano-Monolayer Transition-Metal Dichalcogenides with High 1T′-Phase Purity

Abstract

Phase engineering of nanomaterials provides a promising way to explore the phase-dependent physicochemical properties and various applications of nanomaterials. A general bottom-up synthesis method under mild conditions has always been challenging globally for the preparation of the semimetallic phasetransition-metal dichalcogenide (1T′-TMD) monolayers, which are pursued owing to their unique electrochemical property, unavailable in their semiconducting 2H phases. Here, we report the general scalable colloidal synthesis of nanosized 1T′-TMD monolayers, including 1T′-MoS 2 , 1T′-MoSe 2 , 1T′-WS 2 , and 1T′-WSe 2 , which are revealed to be of high phase purity. Moreover, the surfactantreliant stacking-hinderable growth mechanism of 1T′-TMD nano-monolayers was unveiled through systematic experiments and theoretical calculations. As a proof-of-concept application, the 1T′-TMD nano-monolayers are used for electrocatalytic hydrogen production in an acidic medium. The 1T′-MoS 2 nano-monolayers possess abundant in-plane electrocatalytic active sites and high conductivity, coupled with the contribution of the lattice strain, thus exhibiting excellent performance. Importantly, the catalyst shows impressive endurability in electroactivity. Our developed general scalable strategy could pave the way to extend the synthesis of other broad metastable semimetallic-phase TMDs, which offer great potential to explore novel crystal phase-dependent properties with wide application development for catalysis and beyond.

Charge self-regulation in 1T'''-MoS2 structure with rich S vacancies for enhanced hydrogen evolution activity

“…For 2H-MoS 2 , the Mo L 3 -edge white line peak locates at 2524.01 eV and it is ascribed to the Mo 4+ . The characteristic peak shifts 0.45 eV to lower energy, indicating lower valence state Mo in 1T'''-MoS 2 −10.6% 49 , 50 . The result is consistent with Fig.…”

Untangling the Intertwined: Metallic to Semiconducting Phase Transition in Colloidal MoS2 Nanoplatelets and Nanosheets

“…during the synthesis of MoS 2 , WS 2 and MoSe 2 , WSe 2 NSs. 31,35,[39][40][41] However, the mechanism by which the individual crystal phases are controlled and formed during the synthesis up to now lack systematic description. In order to unlock the potential of colloidal synthesis methods for TMDCs we focus on two critical properties of 2D MoS 2 NSs: The crystal phase and the morphology which we control by variation of the reaction time and concentration of the molybdenum metal precursor.…”

“…36,37 The 1T phase, on the other hand, is metallic, metastable, and typically distorted. 38,39 Wet-chemical TMDC research is focusing increasingly on the respective crystal phases and their formation, e.g. during the synthesis of MoS 2 , WS 2 and MoSe 2 , WSe 2 NSs.…”

Phase Engineering of Metastable Transition Metal Dichalcogenides via Ionic Liquid Assisted Synthesis

“…In the past years, several methods have been developed to synthesize 1T-TMDs, including alkali metal intercalation, − microwave-assisted exfoliation, , heteroatom doping, − electron injection engineering, , defect engineering, , strain control, , high-temperature annealing, − colloidal synthesis, etc. Even though the above methods have achieved success in the synthesis of 1T-TMDs, there are still some problems to be solved, such as the low yield, severe reaction conditions, and high risk reagents. , Additionally, most of the above strategies can only prepare limited types of 1T-TMDs.…”

“…Although 1T-TMDs have extraordinary performance in the field of electrochemistry, the thermodynamical metastability makes 1T-TMDs hard to synthesize directly, greatly restricting their wide applications. 29 In the past years, several methods have been developed to synthesize 1T-TMDs, including alkali metal intercalation, 30−33 microwave-assisted exfoliation, 27,34 heteroatom doping, 35−39 electron injection engineering, 40,41 defect engineering, 42,43 strain control, 44,45 high-temperature annealing, 46−48 colloidal synthesis, 49 etc. Even though the above methods have achieved success in the synthesis of 1T-TMDs, there are still some problems to be solved, such as the low yield, severe reaction conditions, and high risk reagents.…”