High Phase‐Purity 1T‐MoS₂ Ultrathin Nanosheets by a Spatially Confined Template

Abstract

The crystal phase plays an important role in controlling the properties of an anomaterial;h owever,i ti s ag reat challenge to obtain ananomaterial with high purity of the metastable phase.F or instance,the large-scale synthesis of the metallic phase MoS 2 (1T-MoS 2 )isimportant for enhancing electrocatalytic reaction, but it can only be obtained under harsh conditions.Herein, aspatially confined template method is proposed to synthesizeh igh phase-purity MoS 2 with a1 T content of 83 %. Moreover,b oth the confined space and the structure of template will affect the purity of 1T-MoS 2 ;i nt his case,t his approach was extended to other similar spatially confined templates to obtain the high-purity material. The obtained ultrathin nanosheets exhibit good electrocatalytic activity and excellent stability in the hydrogen evolution reaction.Nanomaterials have shown various promising applications in optics, [1] catalysis, [2] and electronics, [3] owing to their unique physiochemical properties,w hich strongly depend on the crystal facet, morphology,d imension, and size.I nr ecent years,t he crystal phase has been reported as an important factor to affect the physical-chemical properties.F or exam-ple,M oS 2 is at ypical polyphase material which includes trigonal (1T), hexagonal (2H), rhombohedral (3R), and 1T' forms. [4] Among them, the unique structure of 1T phase MoS 2 endows it with am etallic-like property, [5] showing higher electrical conductivity and catalytic activity. [6] Nevertheless, the thermodynamically stable phase for MoS 2 is 2H;h ence, the metastable 1T MoS 2 can only be obtained under the harsh synthetic strategies,s uch as alkali metal intercalation-exfoliation, [7] mechanical strain, [8] and electron-beam irradiation. [6a] However,the yields of the aforementioned methods are quite low,w hich severely limits the applications of metallic-phase MoS 2 . [9] It is agreat challenge to obtain high-purity 1T MoS 2 with af acile method. [8] By using the weak interactions between hetero materials, template method is considered as an efficient route to synthesize nanomaterials with metastable phases. [10] Moreover, the confined space will significantly affect the physical and chemical properties of the insert molecules. [11] In this case,t he two-dimensional confined space may induce a2 D nanosheet with metastable phases.T herefore,b yu sing layered Ni(OH) 2 as the spatially confined template,w e successfully synthesized ultrathin MoS 2 nanosheets with the 1T phase of 83 %, which is among the highest 1T ratios obtained with the wet-chemical methods (Supporting Information, Table S1). Af urther study reveals both the space in the confined template and the crystal structure of template will affect the crystal phase of nanomaterials.M oreover,t he ratio between 1T and 2H phases can be easily controlled by adjusting the structure of templates.F urthermore,t he synthesized nanosheets showed an excellent catalytic activity and stability for the hydrogen evolution reaction (HER). Our strategy provides an ew way to...

Atomic Thickness Catalysts: Synthesis and Applications

“…[7,[17][18][19] The ATCs including metals (alloys), LDHs, TMDs, TMOs, carbon based materials, are endowed with higher specific surface and density of unsaturated atoms, providing ideal properties with low-cost, highstability and excellent performance for the energy conversion applications. [3,11,18,[20][21][22][23][24] Exciting breakthroughs of various kinds of ATCs with a controllable morphology, domain size, structure, and composition have been made. [18,25] For instance, Guo's group successfully prepared a free-standing PdMo bimetallene with a thickness of 4-atom, giving a significantly higher atomic utilization >0.5 and a much larger mass activity of oxygen reduction reaction compared with commercial Pt/C and Pd/C, respectively.…”

“…[19,30] Graphene, an atomically thin 2D layered material, has attracted numerous attentions in diversely catalytic applications due to the ultrahigh specific surface area and high electrical conductivity. [31][32][33][34] Meanwhile, other layered ATCs have been developed as well, for example, transition metal dichalcogenides (TMDs), [20,[35][36][37][38][39] MXenes, [40,41] layered double hydroxides (LDHs), [9,27,42,43] graphdiynes (GDY), [44,45] etc. In addition, extensive researches on nonlayered nanostructured ATCs further enriched the exploration of ATCs family members.…”

“…Template-assisted synthesis is another effective approach for the anisotropic growth of various ATCs, including non-noble metals, [68,69] noble metals, [70] metal oxides [71][72][73] and metallic TMDs. [20] In the synthetic strategy assisted with template, the growth of various ATCs can be confined in a given dimension and the thickness, morphology, size of the ATCs are significantly determined by the choice of the selected template. Particularly, the selected template is of paramount importance to affect the crystal structure of the ATCs.…”

“…Particularly, the selected template is of paramount importance to affect the crystal structure of the ATCs. [20] Graphene [69,74,75] and its derivatives [76,77] were recently studied as the most popular hard templates for the synthesis ATCs. For instance, in situ growth of Au square NSs (2.4 nm thickness) on GO sheets could be obtained by using OAm as the reductant and HAuCl 4 as metal precursor.…”

“…[79] Chen et al has synthesized MoS 2 NSs with a 1T content of 83% via a spatially confined template of Ni(OH) 2 . [20] 2H-MoS 2 could be obtained in the presence of Ni(OH) 2 as the template. Additionally, 1T-MoS 2 NSs could also be also obtained with a 1T content of 55% and 75% if using MgAl-LDH or Fe-layered single hydroxide (Fe-LSH), respectively.…”