Method for preparing non-layered two-dimensional transition metal compound by using bulk phase layered transition metal sulfide

Abstract

The invention discloses a method for preparing a non-layered two-dimensional transition metal compound by using a bulk phase layered transition metal sulfide. The method comprises the following steps: firstly, sequentially grinding and uniformly mixing the bulk phase layered transition metal sulfide with sodium carbonate and urea; and then carrying out heat preservation reaction in an auxiliary atmosphere, and carrying out acid pickling, washing, drying and the like to prepare a non-layered two-dimensional transition metal compound nanosheet. According to the method, the two-dimensional transition metal compound nanosheet is efficiently prepared from bulk phase layered transition metal sulfide through a molten salt assisting method, and selective preparation of the two-dimensional carbide or two-dimensional nitride nanosheet is achieved by using urea as a carbon source (or a nitrogen source) and regulating and controlling the reaction atmosphere for the first time. The related synthesis process is simple, the cost is low, the production efficiency is high, the byproduct salt after the reaction is easy to remove, and the method belongs to a green and easy-to-industrialize two-dimensional material preparation process route and is suitable for popularization and industrial application.

Description

technical field [0001] The invention belongs to the technical field of two-dimensional material preparation technology, and in particular relates to a method for preparing non-layered two-dimensional transition metal compound nanosheets from bulk layered transition metal sulfides. Background technique [0002] Carbon and nitride of Mo and W-based transition metals are interstitial compounds. Due to the hybridization of the d orbitals of metal atoms and the s and p orbitals of C atoms (or N atoms), the d-band electronic structures of Mo and W metal carbons and nitrides show a Pt-like electronic structure that makes them compatible With high conductivity and high electrocatalytic activity, it has been widely used in the fields of catalysis and electrochemical energy storage. In addition, compared with bulk materials, two-dimensional Mo, W transition metal carbides (or nitrides), a large number of unsaturated dangling bonds exposed on the surface induce a highly active surface...

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Problems solved by technology

[0003] At present, the methods for synthesizing Mo and W-based two-dimensional carbides (or two-dimensional nitrides) at home and abroad mainly include: 1) Selective etching method, which is prepared by selectively etching A-layer atoms (such as Al, Ga, etc.) in MAX Graphene-like two-dimensional metal carbide (or nitride) MXene material; this method needs to use a large amount of highly corrosive HF or LiF-HCl mixed solution, which is not in line with the development direction of green scale, and the two obtained by chemical etching Dimensional carbides (or nitrides) have a large number of defects (the surface is linked with hydroxyl groups or oxygen-containing functional groups or fluorine-containing terminals), and their stability in water and air is poor

In addition, this method is mainly used for the preparation of carbide MXene materials, and nitride MXene materials are limited to Ti 4 N 3 、Ti 2 N, V 2 N and Mo 2 N, there is no report on W-based MXene materials; 2) Topological transformation method, which prepares two-dimensional carbides (or nitrides) by carbonizing pre-synthesized two-dimensional oxide or sulfide precursors; this method has certain application prospects , however low-cost, high-efficiency and large-scale preparation of two-dimensional MoO 3 or MoS 2 and 2D WO 3 or WS 2 Precursors are still a challenge; 3) chemical vapor deposition method, by selecting a suitable substrate to deposit and grow Mo, W-based two-dimensional carbide (or two-dimensional nitride); this method has low yield and requires extremely high 4) molten salt assisted exfoliation method, such as the literature "Chang H Q, Zhang G H, Chou K C.Topochemical synthesis of two-dimensional molybdenum carbide (Mo 2 C) via Na 2 CO 3 -Assited carbothermal reduction of 2H–MoS 2 [J].Materials Chemistry and Physics,2020,244:122713."In the bulk MoS 2 Powder and Na 2 CO 3 And activated carbon is mixed according to a certain ratio and then calcined in an argon atmosphere, and then the by-products of the molten salt reaction are washed off to prepare two-dimensional molybdenum carbide

The prepared two-dimensional molybdenum carbide utilizes activated carbon as the carbon source, and it is difficult to remove more active carbon remaining and the prepared two-dimensional molybdenum carbide is easy to accumulate; such as the literature "Sun G D, Chang H Q, Zhang G H, et al.A low-cost and efficient pathway for preparation of 2DMoN nanosheets via Na 2 CO 3 -assisted nitridation of MoS 2 with NH 3 [J].Journal of the American Ceramic Society, 2019, 102(12):7178-7186." and literature "Sun G D, Zhang GH, Chou K C.Topochemical synthesis of holey 2D molybdenum nitrides nanosheets via lime-assisted nitridation of layered MoS 2 [J].Ceramics International,2020,46(3):4024-4029."In the use of bulk MoS 2 powder as a precursor with CaO and Na 2 CO 3 After the salt is ground and mixed evenly in NH 3 Calcining under the atmosphere, using molten salt as an auxiliary agent and then cleaning out the by-products to obtain two-dimensional molybdenum nitride; although the above method can obtain a large amount of two-dimensional molybdenum nitride products, it is easy to aggregate into spherical shape and difficult to disperse, and it uses NH 3 As a nitrogen source, an additional ammonia absorption device is required, which increases the synthesis cost and is difficult to produce on a large scale

In addition, there is no report on W-based two-dimensional carbide (or two-dimensional nitride) nanosheets by this synthesis method.

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