scholarly journals Hydrogen spillover-driven synthesis of high-entropy alloy nanoparticles as a robust catalyst for CO2 hydrogenation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kohsuke Mori ◽  
Naoki Hashimoto ◽  
Naoto Kamiuchi ◽  
Hideto Yoshida ◽  
Hisayoshi Kobayashi ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Spillover Effect ◽  
Hydrogenation Reaction ◽  
Hydrogen Spillover ◽  
Advanced Materials ◽  
High Entropy Alloy ◽  
High Entropy ◽  
In Situ Techniques ◽  
Wide Range ◽  
Sluggish Diffusion

AbstractHigh-entropy alloys (HEAs) have been intensively pursued as potentially advanced materials because of their exceptional properties. However, the facile fabrication of nanometer-sized HEAs over conventional catalyst supports remains challenging, and the design of rational synthetic protocols would permit the development of innovative catalysts with a wide range of potential compositions. Herein, we demonstrate that titanium dioxide (TiO2) is a promising platform for the low-temperature synthesis of supported CoNiCuRuPd HEA nanoparticles (NPs) at 400 °C. This process is driven by the pronounced hydrogen spillover effect on TiO2 in conjunction with coupled proton/electron transfer. The CoNiCuRuPd HEA NPs on TiO2 produced in this work were found to be both active and extremely durable during the CO2 hydrogenation reaction. Characterization by means of various in situ techniques and theoretical calculations elucidated that cocktail effect and sluggish diffusion originating from the synergistic effect obtained by this combination of elements.

scholarly journals Hydrogen Spillover-Driven Low Temperature Synthesis of High-Entropy Alloy Nanoparticles as a Robust Catalyst

2021 ◽  
Author(s):  
Kohsuke Mori ◽  
Naoki Hashimoto ◽  
Naoto Kamiuchi ◽  
Hideto Yoshida ◽  
Hisayoshi Kobayashi ◽  
...  
Keyword(s):  
Low Temperature ◽  
Early Stage ◽  
Direct Reduction ◽  
Hydrogen Spillover ◽  
High Entropy Alloy ◽  
Hydrogen Atoms ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
High Entropy ◽  
Wide Range

Abstract High-entropy alloys (HEAs) have been intensively pursued as potentially advanced materials because of their exceptional properties. However, the facile fabrication of nanometer-sized HEAs over conventional catalyst supports remains challenging, and the design of rational synthetic protocols would permit the development of innovative catalysts with a wide range of potential compositions. Herein, we demonstrate that titanium dioxide (TiO2) is a promising platform for the low-temperature synthesis of supported CoNiCuRuPd HEA nanoparticles (NPs) at 400°C. This process is driven by the pronounced hydrogen spillover effect on TiO2 in conjunction with coupled proton/electron transfer. In this process, Pd nuclei generated in the early stage act as uptake sites to enhance the migration of active hydrogen atoms, and the five component metals are simultaneously reduced by spilled hydrogen on the support rather than via direct reduction by gaseous H2. The CoNiCuRuPd HEA NPs on TiO2 produced in this work were found to be both active and extremely durable during the CO2 hydrogenation reaction. Characterization by means of various in situ techniques and theoretical calculations elucidated the specific mechanism by which the HEA NPs were formed and also established that a synergistic effect was obtained from this combination of elements.

scholarly journals Influence of Aluminum and Molybdenum on the Microstructure and Corrosion Behavior of Thermally Sprayed High-Entropy Alloy Coatings

2021 ◽  
Author(s):  
Martin Löbel ◽  
Thomas Lindner ◽  
Maximilian Grimm ◽  
Lisa-Marie Rymer ◽  
Thomas Lampke
Keyword(s):  
Corrosion Resistance ◽  
Protective Coatings ◽  
Base Alloy ◽  
Alloy System ◽  
High Entropy Alloy ◽  
Oxide Content ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Structural And Functional Properties ◽  
Wide Range

AbstractHigh-entropy alloys (HEAs) have shown a wide range of promising structural and functional properties. By the application of coating technology, an economical exploitation can be achieved. The high wear and corrosion resistance of HEAs make them particularly interesting for the application as protective coatings. Especially for alloys with a high chromium content, a high corrosion resistance has been revealed. For the current investigations, the equimolar HEA CrFeCoNi with a single-phase face centered cubic structure is considered as a base alloy system. To increase the corrosion resistance as well as the hardness and strength, the influence of the alloying elements aluminum and molybdenum is analyzed. For the current investigations, the high kinetic process high-velocity oxygen fuel thermal spraying (HVOF) has been considered to produce coatings with a low porosity and oxide content. Feedstock is produced by inert gas atomization. The influence of the alloy composition on the microstructure, phase formation and resulting property profile is studied in detail. A detailed analysis of the corrosion resistance and underlying mechanisms is conducted. The pitting and passivation behavior are investigated by potentiodynamic polarization measurements in NaCl and H2SO4 electrolyte. A distinct improvement of the corrosion resistance can be achieved for the alloy Al0.3CrFeCoNiMo0.2.

scholarly journals Data-Driven Discovery and Synthesis of High Entropy Alloy Hydrides with Targeted Thermodynamic Stability

2021 ◽  
Author(s):  
Matthew Witman ◽  
Gustav Ek ◽  
Sanliang Ling ◽  
Jeffery Chames ◽  
Sapan Agarwal ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Data Driven ◽  
High Entropy Alloy ◽  
Hydrogen Storage Materials ◽  
Equilibrium Pressure ◽  
High Entropy ◽  
Storage Materials ◽  
Composition Space ◽  
Wide Range ◽  
Selection For

Solid-state hydrogen storage materials that are optimized for specific use cases could be a crucial facilitator of the hydrogen economy transition. Yet the discovery of novel hydriding materials has historically been a manual process driven by chemical intuition or experimental trial-and-error. Data-driven materials' discovery paradigms provide an alternative to traditional approaches, whereby machine/statistical learning (ML) models are used to efficiently screen materials for desired properties and significantly narrow the scope of expensive/time-consuming first-principles modeling and experimental validation. Here we specifically focus on a relatively new class of hydrogen storage materials, high entropy alloy (HEA) hydrides, whose vast combinatorial composition space and local structural disorder necessitates a data-driven approach that does not rely on exact crystal structures in order to make property predictions. Our ML model quickly screens hydride stability within a large HEA space and permits down selection for laboratory validation based not only on targeted thermodynamic properties, but also secondary criteria such as alloy phase stability and density. To experimentally verify our predictions, we performed targeted synthesis and characterization of several novel hydrides that demonstrate significant destabilization (70x increase in equilibrium pressure, 20 kJ/molH<sub>2</sub> decrease in desorption enthalpy) relative to the benchmark HEA hydride, TiVZrNbHfH<sub>x</sub>. Ultimately, by providing a large composition space in which hydride thermodynamics can be continuously tuned over a wide range, this work will enable efficient materials selection for various applications, especially in areas such as metal hydride based hydrogen compressors, actuators, and heat pumps.

Molecular Dynamics Study on the Diffusion Process of AuAgCuNiPd High-entropy Alloy Metallurgy Induced by Pulsed Laser Heating

2021 ◽  
Author(s):  
Gen Lin ◽  
Jianwu Guo ◽  
Pengfei Ji
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Laser Heating ◽  
Pulsed Laser ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Alloy Material ◽  
Wide Range ◽  
Pulsed Laser Heating

As a novel alloy material with outstanding mechanical properties, high-entropy alloys have a wide range of promising applications. By establishing individual Au, Ag, Cu, Ni, and Pd nanolaminates with faced-centered-cubic...

scholarly journals Data-Driven Discovery and Synthesis of High Entropy Alloy Hydrides with Targeted Thermodynamic Stability

2021 ◽  
Author(s):  
Matthew Witman ◽  
Gustav Ek ◽  
Sanliang Ling ◽  
Jeffery Chames ◽  
Sapan Agarwal ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Data Driven ◽  
High Entropy Alloy ◽  
Hydrogen Storage Materials ◽  
Equilibrium Pressure ◽  
High Entropy ◽  
Storage Materials ◽  
Composition Space ◽  
Wide Range ◽  
Selection For

Solid-state hydrogen storage materials that are optimized for specific use cases could be a crucial facilitator of the hydrogen economy transition. Yet the discovery of novel hydriding materials has historically been a manual process driven by chemical intuition or experimental trial-and-error. Data-driven materials' discovery paradigms provide an alternative to traditional approaches, whereby machine/statistical learning (ML) models are used to efficiently screen materials for desired properties and significantly narrow the scope of expensive/time-consuming first-principles modeling and experimental validation. Here we specifically focus on a relatively new class of hydrogen storage materials, high entropy alloy (HEA) hydrides, whose vast combinatorial composition space and local structural disorder necessitates a data-driven approach that does not rely on exact crystal structures in order to make property predictions. Our ML model quickly screens hydride stability within a large HEA space and permits down selection for laboratory validation based not only on targeted thermodynamic properties, but also secondary criteria such as alloy phase stability and density. To experimentally verify our predictions, we performed targeted synthesis and characterization of several novel hydrides that demonstrate significant destabilization (70x increase in equilibrium pressure, 20 kJ/molH<sub>2</sub> decrease in desorption enthalpy) relative to the benchmark HEA hydride, TiVZrNbHfH<sub>x</sub>. Ultimately, by providing a large composition space in which hydride thermodynamics can be continuously tuned over a wide range, this work will enable efficient materials selection for various applications, especially in areas such as metal hydride based hydrogen compressors, actuators, and heat pumps.

High-Entropy Alloys – A New Era of Exploitation

2007 ◽  
Vol 560 ◽  
pp. 1-9 ◽  
Author(s):  
Jien Wei Yeh ◽  
Yu Liang Chen ◽  
Su Jien Lin ◽  
Swe Kai Chen
Keyword(s):  
Elevated Temperatures ◽  
Second Law Of Thermodynamics ◽  
Simple Relation ◽  
Atomic Diffusion ◽  
High Entropy Alloy ◽  
New Era ◽  
High Entropy ◽  
Wide Range ◽  
Mechanisms Of Formation ◽  
And Control

A high-entropy alloy (HEA) has been defined by us to have at least five principal elements, each of which has an atomic concentration between 5% and 35%. In the exploration on this new alloy field, we find that HEAs are quite simple to analyze and control, and they might be processed as traditional alloys. There exist many opportunities to create novel alloys, better than traditional ones in a wide range of applications. In this paper, we review the basic microstructural features of HEAs and discuss the mechanisms of formation. Instead of multiple intermetallic phases, the HEAs tend to form simple solid solution phases mainly of cubic crystal structure, especially at elevated temperatures. This tendency is explained by the high entropy effect based on the simple relation: (Gmix = (Hmix – T(Smix, and the second law of thermodynamics. Moreover, nanostructures and amorphous phases are easily formed in HEAs. This tendency is explained by kinetics theory as due to slow atomic diffusion.

scholarly journals Corrosion Behavior of Selectively Laser Melted CoCrFeMnNi High Entropy Alloy

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1029 ◽  
Author(s):  
Jie Ren ◽  
Chaitanya Mahajan ◽  
Liang Liu ◽  
David Follette ◽  
Wen Chen ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Laser Processing ◽  
Electrochemical Impedance ◽  
Processing Parameters ◽  
High Entropy Alloy ◽  
Elemental Distribution ◽  
Powder Bed ◽  
High Entropy ◽  
Wide Range ◽  
Superior Corrosion Resistance

CoCrFeMnNi high entropy alloys (HEAs) were additively manufactured (AM) by laser powder bed fusion and their corrosion resistance in 3.5 wt% NaCl solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy tests. A systematic study of AM CoCrFeMnNi HEAs’ porosity under a wide range of laser processing parameters was conducted and a processing map was constructed to identify the optimal laser processing window for CoCrFeMnNi HEAs. The near fully dense AM CoCrFeMnNi HEAs exhibit a unique non-equilibrium microstructure consisting of tortuous grain boundaries, sub-grain cellular structures, columnar dendrites, associated with some processing defects such as micro-pores. Compared with conventional as-cast counterpart, the AM CoCrFeMnNi HEAs showed higher pitting resistance (ΔE) and greater polarization resistance (Rp). The superior corrosion resistance of AM CoCrFeMnNi HEAs may be attributed to the homogeneous elemental distribution and lower density of micro-pores. Our study widens the toolbox to manufacture HEAs with exceptional corrosion resistance by additive manufacturing.

scholarly journals Engineering sub-2 nm ultrasmall high-entropy alloy nanoparticles with extremely superior performance for hydrogen evolution catalysis

2021 ◽  
Author(s):  
Dingguo Xia ◽  
Guang Feng ◽  
Fanghua Ning ◽  
Jin Song ◽  
Huaifang Shang ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Active Sites ◽  
Large Scale ◽  
Catalytic Mechanism ◽  
Theoretical Calculations ◽  
Superior Performance ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Formidable Challenge ◽  
The Us

Abstract The development of intrinsically effective and low-cost catalysts is critical for the large-scale commercial applications of electrocatalytic hydrogen production. Although various electrocatalysts have demonstrated high activities for hydrogen evolution reaction (HER), it remains a formidable challenge to develop an extremely efficient and durable catalyst for practical use, especially in acidic media. Here, we report quinary ultrasmall NiCoFePtRh high-entropy alloy (us-HEA) nanoparticles (NPs) with extremely superior performance for HER. The us-HEA NPs are well dispersed on the carbon supports, with an average diameter of 1.68 nm, which is the smallest size in the reported HEAs. The us-HEA/C achieves an ultrahigh mass activity of 28.3 A mg-1noble metals (much higher than that of other reported advanced catalysts) at -0.05 V (vs the reversible hydrogen electrode, RHE) for HER in 0.5 M H2SO4 solution, which is 40.4 and 74.5 times higher than those of the commercial Pt/C and Rh/C catalysts, respectively. Moreover, the us-HEA/C demonstrates the highest reported turnover frequency of 30.1 s−1 at 50 mV overpotential (41.8 times higher than that of the Pt/C catalyst) and excellent stability with no decay after 10,000 cycles. Both operando X-ray absorption spectroscopy and theoretical calculations reveal the true active sites and a synergistic effect among five elements, which endow us-HEA/C with significantly enhanced HER activity. This work not only provides a general and facile strategy for synthesizing us-HEA NPs, highlights HEAs as sufficiently advanced materials in energy electrocatalysis, but also acts as a guidance for elucidating the actual reaction process and catalytic mechanism of complex multi-element systems.

Carbothermal shock synthesis of high-entropy-alloy nanoparticles

Science ◽  
2018 ◽  
Vol 359 (6383) ◽  
pp. 1489-1494 ◽  
Author(s):  
Yonggang Yao ◽  
Zhennan Huang ◽  
Pengfei Xie ◽  
Steven D. Lacey ◽  
Rohit Jiji Jacob ◽  
...  
Keyword(s):  
Solid Solution ◽  
Ammonia Oxidation ◽  
Metal Salt ◽  
Shock Duration ◽  
High Entropy Alloy ◽  
Solid Solution Phase ◽  
Alloy Nanoparticles ◽  
Carbon Supports ◽  
High Entropy ◽  
Wide Range

The controllable incorporation of multiple immiscible elements into a single nanoparticle merits untold scientific and technological potential, yet remains a challenge using conventional synthetic techniques. We present a general route for alloying up to eight dissimilar elements into single-phase solid-solution nanoparticles, referred to as high-entropy-alloy nanoparticles (HEA-NPs), by thermally shocking precursor metal salt mixtures loaded onto carbon supports [temperature ~2000 kelvin (K), 55-millisecond duration, rate of ~105 K per second]. We synthesized a wide range of multicomponent nanoparticles with a desired chemistry (composition), size, and phase (solid solution, phase-separated) by controlling the carbothermal shock (CTS) parameters (substrate, temperature, shock duration, and heating/cooling rate). To prove utility, we synthesized quinary HEA-NPs as ammonia oxidation catalysts with ~100% conversion and >99% nitrogen oxide selectivity over prolonged operations.

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