Showing papers by "Yonggang Yao published in 2022"

High-entropy nanoparticles: Synthesis-structure-property relationships and data-driven discovery

Abstract: High-entropy nanoparticles have become a rapidly growing area of research in recent years. Because of their multielemental compositions and unique high-entropy mixing states (i.e., solid-solution) that can lead to tunable activity and enhanced stability, these nanoparticles have received notable attention for catalyst design and exploration. However, this strong potential is also accompanied by grand challenges originating from their vast compositional space and complex atomic structure, which hinder comprehensive exploration and fundamental understanding. Through a multidisciplinary view of synthesis, characterization, catalytic applications, high-throughput screening, and data-driven materials discovery, this review is dedicated to discussing the important progress of high-entropy nanoparticles and unveiling the critical needs for their future development for catalysis, energy, and sustainability applications. Description BACKGROUND High-entropy nanoparticles contain more than four elements uniformly mixed into a solid-solution structure, offering opportunities for materials discovery, property optimization, and advanced applications. For example, the compositional flexibility of high-entropy nanoparticles enables fine-tuning of the catalytic activity and selectivity, and high-entropy mixing offers structural stability under harsh operating conditions. In addition, the multielemental synergy in high-entropy nanoparticles provides a diverse range of adsorption sites, which is ideal for multistep tandem reactions or reactions that require multifunctional catalysts. However, the wide range of possible compositions and complex atomic arrangements also create grand challenges in synthesizing, characterizing, understanding, and applying high-entropy nanoparticles. For example, controllable synthesis is challenging given the different physicochemical properties within the multielemental compositions combined with the small size and large surface area. Moreover, random multielemental mixing can make it difficult to precisely characterize the individual nanoparticles and their statistical variations. Without rational understanding and guidance, efficient compositional design and performance optimization within the huge multielemental space is nearly impossible. ADVANCES The comprehensive study of high-entropy nanoparticles has become feasible because of the rapid development of synthetic approaches, high-resolution characterization, high-throughput experimentation, and data-driven discovery. A diverse range of compositions and material libraries have been developed, many by using nonequilibrium “shock”–based methods designed to induce single-phase mixing even for traditionally immiscible elemental combinations. The nanomaterial types have also rapidly evolved from crystalline metallic alloys to metallic glasses, oxides, sulfides, phosphates, and others. Advanced characterization tools have been used to uncover the structural complexities of high-entropy nanoparticles. For example, atomic electron tomography has been used for single-atom-level resolution of the three-dimensional positions of the elements and their chemical environments. Finally, high-entropy nanoparticles have already shown promise in a wide range of catalysis and energy technologies because of their atomic structure and tunable electronic states. The development of high-throughput computational and experimental methods can accelerate the material exploration rate and enable machine-learning tools that are ideal for performance prediction and guided optimization. Materials discovery platforms, such as high-throughput exploration and data mining, may disruptively supplant conventional trial-and-error approaches for developing next-generation catalysts based on high-entropy nanoparticles. OUTLOOK High-entropy nanoparticles provide an enticing material platform for different applications. Being at an initial stage, enormous opportunities and grand challenges exist for these intrinsically complex materials. For the next stage of research and applications, we need (i) the controlled synthesis of high-entropy nanoparticles with targeted surface compositions and atomic arrangements; (ii) fundamental studies of surfaces, ordering, defects, and the dynamic evolution of high-entropy nanoparticles under catalytic conditions through precise structural characterization; (iii) identification and understanding of the active sites and performance origin (especially the enhanced stability) of high-entropy nanoparticles; and (iv) high-throughput computational and experimental techniques for rapid screening and data mining toward accelerated exploration of high-entropy nanoparticles in a multielemental space. We expect that discoveries about the synthesis-structure-property relationships of high-entropy nanoparticles and their guided discovery will greatly benefit a range of applications for catalysis, energy, and sustainability. High-entropy nanoparticles and data-driven discovery. Emerging high-entropy nanoparticles feature multielemental mixing within a large compositional space and can be used for diverse applications, particularly for catalysis. High-throughput and machine-learning tools, coupled with advanced characterization techniques, can substantially accelerate the optimization of these high-entropy nanoparticles, forming a closed-loop paradigm toward data-driven discovery. CREDITS: TOP RIGHT: YANG ET AL., NATURE 592, 60–64 (2021); CENTER: JIAQI DAI; BOTTOM RIGHT: XIE ET AL., NAT. COMMUN.10, 4011 (2019) Diversifying nanoparticles Multielement nanoparticles are attractive for a variety of applications in catalysis, energy, and other fields. A more diverse range and larger number of elements can be mixed together because of high-entropy mixing states accessed by a number of recently developed techniques. Yao et al. review these techniques along with characterization methods, high-throughput screening, and data-driven discovery for targeted applications. The wide range of different elements that can be mixed together presents a large number of opportunities and challenges. —BG A review highlights improvements in synthesizing and stabilizing multielement nanoparticles.

Multi-principal elemental intermetallic nanoparticles synthesized via a disorder-to-order transition

Abstract: Nanoscale multi-principal element intermetallics (MPEIs) may provide a broad and tunable compositional space of active, high–surface area materials with potential applications such as catalysis and magnetics. However, MPEI nanoparticles are challenging to fabricate because of the tendency of the particles to grow/agglomerate or phase-separated during annealing. Here, we demonstrate a disorder-to-order phase transition approach that enables the synthesis of ultrasmall (4 to 5 nm) and stable MPEI nanoparticles (up to eight elements). We apply just 5 min of Joule heating to promote the phase transition of the nanoparticles into L10 intermetallic structure, which is then preserved by rapidly cooling. This disorder-to-order transition results in phase-stable nanoscale MPEIs with compositions (e.g., PtPdAuFeCoNiCuSn), which have not been previously attained by traditional synthetic methods. This synthesis strategy offers a new paradigm for developing previously unexplored MPEI nanoparticles by accessing a nanoscale-size regime and novel compositions with potentially broad applications.

High‐entropy alloy stabilized and activated Pt clusters for highly efficient electrocatalysis

Abstract: Although Pt and other noble metals are the state‐of‐the‐art catalysts for various energy conversion applications, their low reserve, high cost, and instability limit their large‐scale utilization. Herein, we report a hybrid catalysts design featuring noble metal clusters (e.g., Pt) uniformly dispersed and stabilized on high‐entropy alloy nanoparticles (HEA, e.g., FeCoNiCu), denoted as HEA@Pt, which is prepared via ultra‐fast shock synthesis (∼300 ms) for HEA alloying combined with Pt galvanic replacement for surface anchoring. In our design, the HEA core critically ensures high dispersity, stability, and tunability of the surface Pt clusters through high entropy stabilization and core‐shell interactions. As an example in the hydrogen evolution reaction, HEA@Pt achieved a significant mass activity of 235 A/gPt, which is 9.4, 3.6, and 1.9‐times higher compared to that of homogeneous FeCoNiCuPt (HEA‐Pt), Pt, and commercial Pt/C, respectively. We also demonstrated noble Ir stabilized on FeCoNiCrMn nanoparticles (HEA‐5@Ir), achieving excellent anodic oxygen evolution performance and highly efficient overall water splitting when combined with the cathodic HEA@Pt. Therefore, our work developed a general catalysts design strategies by using high entropy nanoparticles for effective dispersion, stabilization, and modulation of surface active sites, achieving a harmonious combination of high activity, stability, and low cost.

High‐entropy alloy catalysts: From bulk to nano toward highly efficient carbon and nitrogen catalysis

Abstract: High-entropy alloys (HEAs) have attracted widespread attention as both structural and functional materials owing to their huge multielement composition space and unique high-entropy mixing structure. Recently, emerging HEAs, either in nano or highly porous bulk forms, are developed and utilized for various catalytic and clean energy applications with superior activity and remarkable durability. Being catalysts, HEAs possess some unique advantages, including (1) a multielement composition space for the discovery of new catalysts and fine-tuning of surface adsorption (i.e., activity and selectivity), (2) diverse active sites derived from the random multielement mixing that are especially suitable for multistep catalysis, and (3) a high-entropy stabilized structure that improves the structural durability in harsh catalytic environments. Benefited from these inherent advantages, HEA catalysts have demonstrated superior catalytic performances and are promising for complex carbon (C) and nitrogen (N) cycle reactions featuring multistep reaction pathways and many different intermediates. However, the design, synthesis, characterization, and understanding of HEA catalysts for C- and N-involved reactions are extremely challenging because of both complex high-entropy materials and complex reactions. In this review, we present the recent development of HEA catalysts, particularly on their innovative and extensive syntheses, advanced (in situ) characterizations, and applications in complex C and N looping reactions, aiming to provide a focused view on how to utilize intrinsically complex catalysts for these important and complex reactions. In the end, remaining challenges and future directions are proposed to guide the development and application of HEA catalysts for highly efficient energy storage and chemical conversion toward carbon neutrality.

Surface‐Decorated High‐Entropy Alloy Catalysts with Significantly Boosted Activity and Stability

Abstract: High‐entropy alloy (HEA) nanoparticles are emerging catalytic materials and are particularly attractive for multi‐step reactions due to their diverse active sites and multielement tunability. However, their design and optimization often involve lengthy efforts due to the vast multielement space and unidentified active sites. Herein, surface decoration of HEA nanoparticles to drastically improve the overall activity, stability, and reduce cost is reported. A two‐step process is employed to first synthesize non‐noble HEA (FeCoNiSn) nanoparticles and then are surface alloyed with Pd (main active site), denoted as NHEA@NHEA‐Pd. As a demonstration in the ethanol oxidation reaction, a high mass activity of 7.34 A mg−1Pd and superior stability (>91.8% retention after 2000 cycles) in NHEA@NHEA‐Pd are achieved, substantially outperforming traditional HEA, binary M@M‐Pd (M = Sn, Fe, Co, Ni), and commercial Pd/C. In situ spectroscopy reveals that NHEA@NHEA‐Pd can catalytically produce and oxidize CO at <0.5 V, which is >200 mV lower than Sn@Sn‐Pd, suggesting enhanced activity in NHEA@NHEA‐Pd owing to Pd's unique high‐entropy coordination environment. This work provides a novel design of HEA catalysts by combining surface decoration (exposing more active sites) and high‐entropy coordination (enhancing intrinsic activity and structural stability) to boost catalysts’ activity and durability.

Rapid Synthesis of High-Entropy Oxide Microparticles.

Abstract: High-entropy nanoparticles have received notable attention due to their tunable properties and broad material space. However, these nanoparticles are not suitable for certain applications (e.g., battery electrodes), where their microparticle (submicron to micron) counterparts are more preferred. Conventional methods used for synthesizing high-entropy nanoparticles often involve various ultrafast shock processes. To increase the size thereby achieving high-entropy microparticles, longer reaction time (e.g., heating duration) is usually used, which may also lead to undesired particle overgrowth or even densified microstructures. In this work, an approach based on Joule heating for synthesizing high-entropy oxide (HEO) microparticles with uniform elemental distribution is reported. In particular, two key synthesis conditions are identified to achieve high-quality HEO microparticles: 1) the precursors need to be loosely packed to avoid densification; 2) the heating time needs to be accurately controlled to tens of seconds instead of using milliseconds (thermal shock) that leads to nanoparticles or longer heating duration that forms bulk structures. The utility of the synthesized HEO microparticles for a range of applications, including high-performance Li-ion battery anode and water oxidation catalyst. This study opens up a new door toward synthesizing high-entropy microparticles with high quality and broad material space.

Anisotropy-inspired, simulation-guided design and 3D printing of microlattice metamaterials with tailored mechanical-transport performances

Abstract: Rapid development in 3D printing technology has stimulated enthusiasm in the functional design of metamaterials with unique properties, in which multiple properties should be simultaneously optimized. However, this is challenging because different properties, such as mechanical and mass-transport properties, are often coupled strongly and cannot be adjusted independently. Herein, we propose an anisotropy-inspired and simulation-guided microlattice metamaterial design strategy that realizes independent tailoring of the elastic response and fluid transport performances. Diamond microlattice metamaterials are used for demonstration, constructed by using different facets ([001], [110] and [111]) and rotation degrees (15°/step), inspired from the atoms’ arrangements. Through computational analyses, it is proven that the coupled relationship of mechanical and transport properties are abated and have directional dependence on crystal planes and orientation directions. Three microlattice metamaterials and a gradient microlattice metamaterial were fabricated by 3D printing for experimental verification. The assigned layer-by-layer deformation process and specific mass-transport characteristic of the gradient microlattice metamaterial were easily endowed. This study offers an approach to decouple synergy and enable separate tailoring for multi-physical metamaterials in a much larger performance regulation space, which can effectively guide simultaneous improvements toward practical applications.

Controlled Nutrient Delivery through a pH-Responsive Wood Vehicle.

Abstract: To lower the risk of disease and improve health, many nutrients benefit from intestinal-targeted delivery. Here, we present a nutrient-delivery system based on a pH-responsive "wood scroll", in which nutrients are stored, protected, and controllably released through the rolled structure and natural microchannels of a flexible wood substrate, thus ensuring higher bioactivity as well as prolonged steady release of the nutrient load to the intestine. We loaded the wood's natural microchannels with probiotics as a proof-of-concept demonstration. The probiotic-loaded wood scrolls can survive the simulated conditions of the stomach with a high survival rate (95.40%) and exhibit prolonged release (8 h) of the probiotic load at a constant release rate (4.17 × 108 CFUs/h) in the simulated conditions of the intestine. Moreover, by modifying the macroscopic geometry and microstructures of the wood scrolls, both the nutrient loading and release behaviors can be tuned over a wide range for customized or personalized nutrient management. The wood scrolls can also deliver other types of nutrients, as we demonstrate for tea polyphenols and rapeseed oil. This wood scroll design illustrates a promising structurally controlled strategy for the delivery of enteric nutrients using readily available, low-cost, and biocompatible biomass materials that have a naturally porous structure for nutrient storage, protection, and controlled release.

Bioinspired, Simulation‐Guided Design of Polyhedron Metamaterial for Simultaneously Efficient Heat Dissipation and Energy Absorption

Abstract: Light‐weight, high‐strength metamaterials with excellent heat dissipation and energy absorption capabilities are of great interest to aerospace and automobile applications. Particularly, innovative structure design and its successful realization are paramount but often challenging due to the vast design space and associated complex manufacturing. Herein, in this study, inspired by pomelo peel's superior shielding protection to the pulp, bionic polyhedron metamaterials (BPMs) that imitate the pomelo peel are designed and realized by metal 3D printing to achieve not only superior heat dissipation but also high energy absorption. Guided by experiments and numerical simulations, the BPM with circular struts possesses the highest Nusselt number, lowest pressure drop, and friction factor at Re = 7000–30000. Above results integrated lead to that the BPM with circular struts exhibit a higher thermal efficiency index that exceeds 1 at 0.92 porosity. Furthermore, the BPM with circular struts possesses moderate specific energy absorption in existing mechanical metamaterials for their corresponding density, which has potential for gas turbines and some cooling structures. The above findings will guide the design of metamaterials with high heat dissipation and energy absorption.

In-situ zinc cyanamide coordination induced highly N-rich graphene for efficient peroxymonosulfate activation

Abstract: Nitrogen-doped graphene represents a promising material platform for various catalytic reactions, yet the low nitrogen (N, which often serves as the active site) contents and limited tunability among different N...

A general method for rapid synthesis of refractory carbides by low-pressure carbothermal shock reduction

Abstract: Significance Refractory carbides are emerging as attractive candidates for support materials in heterogeneous catalysis. However, the industrial applications of refractory carbides, especially silicon carbide (SiC), are greatly hampered because of its low surface area and harsh synthetic conditions during available industrial preparation process. Based on Le Chatelier’s principle, we theoretically proposed and experimentally verified that a low-pressure carbothermal reduction strategy was capable of rapid and scalable synthesis of SiC with remarkably high surface area to satisfy the industrial requirement. Furthermore, our strategy is also applicable to the rapid synthesis of refractory metal carbides and even their emerging high-entropy carbides. The rapid synthesis of carbide-based advanced functional materials is beneficial for their performance research and industrial applications.

Interface Engineering Between Multi‐Elemental Alloy Nanoparticles and a Carbon Support Toward Stable Catalysts (Adv. Mater. 9/2022)

Abstract: Hierarchical Catalysts In article number 2106436, Liangbing Hu and co-workers report an interface engineering strategy to improve the stability of multi-elemental alloy (MEA) nanoparticles on a carbon substrate. The MEA-oxide–carbon hierarchical catalysts synthesized by a rapid high-temperature shock method demonstrate excellent thermal and electrochemical stabilities, and hold great promise for various catalytic applications.

Determining the 3D Atomic Structure of Metallic Glass

Abstract: 1. Department of Physics & Astronomy, STROBE NSF Science & Technology Center and California NanoSystems Institute, University of California, Los Angeles, CA, USA. 2. Department of Mathematics, University of California, Los Angeles, CA, USA. 3. Department of Materials Science and Engineering, University of Maryland, College Park, MD, USA 4. National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, USA. * Corresponding author: miao@physics.ucla.edu

A LUNet based on large kernel attention mechanism for image denoising

Abstract: U-shaped networks are widely used in the field of image denoising with their multiscale and jump connection structures in recent years. The feature extraction structures mainly used in previous works are convolutional neural networks (CNNs), but their ability to extract information at a distance is poor. In this paper, we propose a U-shaped network structure combined with large kernel attention structure for image denoising, in which the CNNs structure can effectively extract local information while the large kernel attention structure has better extraction of global information and lower computational cost compared with Transformer, through which local-global features are learned on the feature maps of the input noisy images at different scales, which can effectively enhance the performance of the network and improve the image denoising task. The performance of the network can be enhanced to improve the performance of the image denoising task.