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Two-dimensional materials, including typical graphene, carbon nitride (g-C3N4), transition metal hydroxides, transition metal sulfides, phosphides, MXenes and two-dimensional metal organic frameworks (MOFs), etc., whose thickness is usually in a single From the atomic layer to several atomic layers, it has a high specific surface area and exposes a large number of active sites. Therefore, two-dimensional materials are widely used in catalysis, energy storage, biomedicine and other fields.

Recently, two-dimensional materials frequently appear in various top journals. Here are some special reports on the application of such materials in the fields of catalysis and energy storage. 1one

Direct ethanol fuel cell has the advantages of high energy density, convenient storage and transportation, and is an extremely attractive energy conversion device. However, the anode reaction of DEFCs, the ethanol oxidation reaction (EOR), has low selectivity to the C1 pathway (to CO2), and high selectivity to the C2 pathway (to CH3COOH), resulting in the utilization efficiency of this type of energy device Poor. In view of this, Yong Xu of Guangdong University of Technology, Huang Xiaoqing of Soochow University and others synthesized SnO2-Rh nanosheets (NSs) by solvothermal method and found that the high selectivity of EOR to C1 pathway can be achieved at the Rh-SnO2 interface. . The optimized 0.2SnO2-Rh NSs/C catalyst has good basic EOR activity and stability, and its mass activity is as high as 213.2 mA mgRh-1, among which the Faraday efficiency of the C1 pathway is 72.8%, which is that of the Rh NSs/C catalyst. 1.7 and 1.9 times. Mechanism studies have shown that the strong synergistic effect of the Rh-SnO2 interface significantly promotes the cleavage of C-C bonds in C2H5OH, is beneficial to the formation of CO2, and promotes the oxidation of toxic intermediate products (*CO and *CH3), effectively inhibiting catalyst deactivation.

Selective Ethanol Oxidation Reaction at the Rh–SnO2 Interface, Advanced Materials, 2020.

https://onlinelibrary.wiley.com/doi/10.1002/adma.2020057672one

Two-dimensional transition metal carbides and nitrides (MXenes) are a new class of two-dimensional materials in recent years. Due to their unique electronic, physical, chemical and mechanical properties, they have been proven to be high-performance electrocatalysts. Han You of Tianjin University, Chen Jingguang of Brookhaven National Laboratory and others reviewed various synthetic methods of MXenes, discussed the development trend and latest progress of MXenes in electrocatalysis, including HER, OER, ORR, CO2RR, N2RR and MOR (Methanol Oxidation Reaction). Then, the author discussed the design of MXenes electrocatalyst, and its experimental and theoretical challenges and opportunities.

Challenges and Opportunities in Utilizing MXenes of Carbides and Nitrides as Electrocatalysts, Advanced Energy Materials, 2020.

https://onlinelibrary.wiley.com/doi/10.1002/aenm.2020029673one

Due to problems such as slow electrochemical reaction kinetics and poor cycle stability, the development of electrochemical energy storage technology has been seriously affected. Therefore, it is necessary to carefully design a functional electrode material with a specific structure and composition, which plays a key role in improving its inherent activity. In particular, the catalysts (SAs@2D) that form single-atom sites in the ultra-thin two-dimensional framework can cause strong electronic interactions through the synergistic effect between the ultra-thin support and isolated atomic sites to form a large number of The coordination unsaturation center of the catalyst can regulate the activity, selectivity and stability of the catalyst. Therefore, Yin Longwei of Shandong University and others systematically summarized the new methods of synthesizing SAs@2D catalysts at home and abroad in recent years, such as defect engineering strategies, coordination engineering strategies and atom substitution strategies. The author introduced the current understanding of the structure-activity mechanism of catalytic performance and long-term durability through coordination geometry and metal-support interaction. Then the application of electrochemical energy storage based on SAs@2D catalyst is discussed in detail, and finally the challenges and application prospects of this kind of materials in the field of rechargeable batteries are prospected.

Two-dimensional matrices confining metal single atoms with enhanced electrochemical reaction kinetics for energy storage applications, Energy & Environmental Science, 2020.

https://pubs.rsc.org/en/Content/ArticleLanding/2020/EE/D0EE02651D#!divAbstract4one

The long ion channels in two-dimensional materials greatly limit the electrochemical performance of practical dense membrane electrodes (loading> 10 mg cm-2). Typical strategies, such as introducing other nanomaterials or designing three-dimensional structures, usually sacrifice the volume-specific capacitance of the Ti3C2Tx electrode to improve its rate performance, thereby failing to show the advantages of the Ti3C2Tx electrode compared to other materials. In view of this, Pan Feng of Peking University Shenzhen Graduate School, Xu Baomin of Southern University of Science and Technology, Yury Gogotsi of Drexel University, and others have proposed a new, simple and controllable oxidation method that does not affect or destroy the future. In the case of etched part of the crystal structure, Ti3C2Tx nanosheets can be oxidized by concentrated H2SO4 and partly etched, which also leads to an increase in the distance between atomic layers. The use of electrochemically active by-products such as TiO2 suppresses the re-stacking of Ti3C2Tx films. The Ti3C2Tx film with layered ion channels has the characteristics of porous structure, enlarged atomic layer spacing, smaller sheet size, etc., which enables it to have both excellent rate performance and high volumetric capacitance.

Optimizing Ion Pathway in Titanium Carbide MXene for Practical High-Rate Supercapacitor, Advanced Energy Materials, 2020.

https://onlinelibrary.wiley.com/doi/10.1002/aenm.2020030255one

Since the oxygen evolution reaction OER carried out by the anode of the water electrolysis reaction involves a complex 4-electron transfer process, the kinetic reaction is slow, and the efficiency of producing H2 from electrolysis water is still not high. Therefore, the use of hydrazine oxidation reaction (HzOR) to replace OER has been affected. Great attention. In view of this, Xiao Chong, Zhang Genqiang, Xie Yi and others of the University of Science and Technology of China reported that Ni3N-Co3N nanosheet arrays with a layered porous structure grown on foamed nickel can be used as high-efficiency HER and HzOR electrodes. The working potential is -43 mV and -88 mV at 10 mA cm-2, especially when the current density of HzOR reaches the industrial level (1000 mA cm-2), the working potential is only 200 mV. The overall hydrazine decomposition device assembled by the electrode has working potentials of 0.071 and 0.76 V at current densities of 10 and 400 mA cm-2, respectively. The combined use of direct hydrazine fuel cells (DHzFC) and commercial solar cells has also been studied. In the production of H2, it provides a feasible way for future practical applications. The DFT calculation explained the Ni3N-Co3N heterogeneous interface while simultaneously optimizing the free energy of hydrogen adsorption (∆GH*) and promoting the dehydrogenation kinetics of hydrazine.