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1. 2D High‐Entropy Transition Metal Dichalcogenides for Carbon Dioxide Electrocatalysis

   https://doi.org/10.1002/adma.202100347  

   Cavin, John; Ahmadiparidari, Alireza; Majidi, Leily; Thind, Arashdeep Singh; Misal, Saurabh N.; Prajapati, Aditya; Hemmat, Zahra; Rastegar, Sina; Beukelman, Andrew; Singh, Meenesh R.; et al (June 2021, Advanced Materials)

   null (Ed.)

   High-entropy alloys combine multiple principal elements at a near equal fraction to form vast compositional spaces to achieve outstanding functionalities that are absent in alloys with one or two principal elements. Here, the prediction, synthesis, and multiscale characterization of 2D high-entropy transition metal dichalcogenide (TMDC) alloys with four/five transition metals is reported. Of these, the electrochemical performance of a five-component alloy with the highest configurational entropy, (MoWVNbTa)S2, is investigated for CO2 conversion to CO, revealing an excellent current density of 0.51 A cm−2 and a turnover frequency of 58.3 s−1 at ≈ −0.8 V versus reversible hydrogen electrode. First-principles calculations show that the superior CO2 electroreduction is due to a multi-site catalysis wherein the atomic-scale disorder optimizes the rate-limiting step of CO desorption by facilitating isolated transition metal edge sites with weak CO binding. 2D high-entropy TMDC alloys provide a materials platform to design superior catalysts for many electrochemical systems. 

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2. Quasi‐Binary Transition Metal Dichalcogenide Alloys: Thermodynamic Stability Prediction, Scalable Synthesis, and Application

   https://doi.org/10.1002/ADMA.201907041  

   Hemmat, Zahra; Cavin, John; Ahmadiparidari, Alireza; Ruckel, Alexander; Rastegar, Sina; Misal, Saurabh N.; Majidi, Leily; Kumar, Khagesh; Wang, Shuxi; Guo, Jinglong; et al (May 2020, Advanced Materials)

   Transition metal dichalcogenide (TMDCs) alloys could have a wide range of physical and chemical properties, ranging from charge density waves to superconductivity and electrochemical activities. While many exciting behaviors of unary TMDCs have been demonstrated, the vast compositional space of TMDC alloys has remained largely unexplored due to the lack of understanding regarding their stability when accommodating different cations or chalcogens in a single‐phase. Here, a theory‐guided synthesis approach is reported to achieve unexplored quasi‐binary TMDC alloys through computationally predicted stability maps. Equilibrium temperature–composition phase diagrams using first‐principles calculations are generated to identify the stability of 25 quasi‐binary TMDC alloys, including some involving non‐isovalent cations and are verified experimentally through the synthesis of a subset of 12 predicted alloys using a scalable chemical vapor transport method. It is demonstrated that the synthesized alloys can be exfoliated into 2D structures, and some of them exhibit: i) outstanding thermal stability tested up to 1230 K, ii) exceptionally high electrochemical activity for the CO2 reduction reaction in a kinetically limited regime with near zero overpotential for CO formation, iii) excellent energy efficiency in a high rate Li–air battery, and iv) high break‐down current density for interconnect applications. This framework can be extended to accelerate the discovery of other TMDC alloys for various applications. 

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3. Quasi‐Binary Transition Metal Dichalcogenide Alloys: Thermodynamic Stability Prediction, Scalable Synthesis, and Application

   https://doi.org/10.1002/adma.201907041  

   Hemmat, Zahra; Cavin, John; Ahmadiparidari, Alireza; Ruckel, Alexander; Rastegar, Sina; Misal, N Saurabh; Majidi, Leily; Kumar, Khagesh; Wang, Shuxi; Guo, Jinglong; et al (May 2020, Advanced materials)

   Transition metal dichalcogenide (TMDCs) alloys could have a wide range of physical and chemical properties, ranging from charge density waves to superconductivity and electrochemical activities. While many exciting behaviors of unary TMDCs have been demonstrated, the vast compositional space of TMDC alloys has remained largely unexplored due to the lack of understanding regarding their stability when accommodating different cations or chalcogens in a single‐phase. Here, a theory‐guided synthesis approach is reported to achieve unexplored quasi‐binary TMDC alloys through computationally predicted stability maps. Equilibrium temperature–composition phase diagrams using first‐principles calculations are generated to identify the stability of 25 quasi‐binary TMDC alloys, including some involving non‐isovalent cations and are verified experimentally through the synthesis of a subset of 12 predicted alloys using a scalable chemical vapor transport method. It is demonstrated that the synthesized alloys can be exfoliated into 2D structures, and some of them exhibit: i) outstanding thermal stability tested up to 1230 K, ii) exceptionally high electrochemical activity for the CO2 reduction reaction in a kinetically limited regime with near zero overpotential for CO formation, iii) excellent energy efficiency in a high rate Li–air battery, and iv) high break‐down current density for interconnect applications. This framework can be extended to accelerate the discovery of other TMDC alloys for various applications. 

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4. Functional two-dimensional high-entropy materials

   https://doi.org/10.1038/s43246-023-00341-y  

   Nemani, Srinivasa Kartik; Torkamanzadeh, Mohammad; Wyatt, Brian C.; Presser, Volker; Anasori, Babak (December 2023, Communications Materials)

   Abstract Multiple principal element or high-entropy materials have recently been studied in the two-dimensional (2D) materials phase space. These promising classes of materials combine the unique behavior of solid-solution and entropy-stabilized systems with high aspect ratios and atomically thin characteristics of 2D materials. The current experimental space of these materials includes 2D transition metal oxides, carbides/carbonitrides/nitrides (MXenes), dichalcogenides, and hydrotalcites. However, high-entropy 2D materials have the potential to expand into other types, such as 2D metal-organic frameworks, 2D transition metal carbo-chalcogenides, and 2D transition metal borides (MBenes). Here, we discuss the entropy stabilization from bulk to 2D systems, the effects of disordered multi-valent elements on lattice distortion and local electronic structures and elucidate how these local changes influence the catalytic and electrochemical behavior of these 2D high-entropy materials. We also provide a perspective on 2D high-entropy materials research and its challenges and discuss the importance of this emerging field of nanomaterials in designing tunable compositions with unique electronic structures for energy, catalytic, electronic, and structural applications. 

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5. Recent progress of high-entropy materials for energy storage and conversion

   https://doi.org/10.1039/d0ta09578h  

   Amiri, Azadeh; Shahbazian-Yassar, Reza (January 2021, Journal of Materials Chemistry A)

   null (Ed.)

   The emergence of high-entropy materials (HEMs) with their excellent mechanical properties, stability at high temperatures, and high chemical stability is poised to yield new advancement in the performance of energy storage and conversion technologies. This review covers the recent developments in catalysis, water splitting, fuel cells, batteries, supercapacitors, and hydrogen storage enabled by HEMs covering metallic, oxide, and non-oxide alloys. Here, first, the primary rules for the proper selection of the elements and the formation of a favorable single solid solution phase in HEMs are defined. Furthermore, recent developments in different fields of energy conversion and storage achieved by HEMs are discussed. Higher electrocatalytic and catalytic activities with longer cycling stability and durability compared to conventional noble metal-based catalysts are reported for high-entropy materials. In electrochemical energy storage systems, high-entropy oxides and alloys have shown superior performance as anode and cathode materials with long cycling stability and high capacity retention. Also, when used as metal hydrides for hydrogen storage, remarkably high hydrogen storage capacity and structural stability are observed for HEMs. In the end, future directions and new energy-related technologies that can be enabled by the application of HEMs are outlined. 

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