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Your search keyword '"Chi, Miaofang"' showing total 27 results
Start Over Author "Chi, Miaofang" Journal journal of the american chemical society
27 results on '"Chi, Miaofang"'

1. Unveiling the Stability of Encapsulated Pt Catalysts Using Nanocrystals and Atomic Layer Deposition

Author

Liccardo, Gennaro, Cendejas, Melissa C., Mandal, Shyama C., Stone, Michael L., Porter, Stephen, Nhan, Bang T., Kumar, Abinash, Smith, Jacob, Plessow, Philipp N., Cegelski, Lynette, Osio-Norgaard, Jorge, Abild-Pedersen, Frank, Chi, Miaofang, Datye, Abhaya K., Bent, Stacey F., and Cargnello, Matteo

Abstract

Platinum exhibits desirable catalytic properties, but it is scarce and expensive. Optimizing its use in key applications such as emission control catalysis is important to reduce our reliance on such a rare element. Supported Pt nanoparticles (NPs) used in emission control systems deactivate over time because of particle growth in sintering processes. In this work, we shed light on the stability against sintering of Pt NPs supported on and encapsulated in Al2O3using a combination of nanocrystal catalysts and atomic layer deposition (ALD) techniques. We find that small amounts of alumina overlayers created by ALD on preformed Pt NPs can stabilize supported Pt catalysts, significantly reducing deactivation caused by sintering, as previously observed by others. Combining theoretical and experimental insights, we correlate this behavior to the decreased propensity of oxidized Pt species to undergo Ostwald ripening phenomena because of the physical barrier imposed by the alumina overlayers. Furthermore, we find that highly stable catalysts can present an abundance of under-coordinated Pt sites after restructuring of both Pt particles and alumina overlayers at a high temperature (800 °C) in C3H6oxidation conditions. The enhanced stability significantly improves the Pt utilization efficiency after accelerated aging treatments, with encapsulated Pt catalysts reaching reaction rates more than two times greater than those of a control supported Pt catalyst.

Published
2024
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3. Au/Pt Bimetallic Nanowires with Stepped Pt Sites for Enhanced C–C Cleavage in C2+ Alcohol Electro-oxidation Reactions

Author

Wei, Kecheng, primary, Lin, Honghong, additional, Zhao, Xueru, additional, Zhao, Zhonglong, additional, Marinkovic, Nebojsa, additional, Morales, Michael, additional, Huang, Zhennan, additional, Perlmutter, Laura, additional, Guan, Huanqin, additional, Harris, Cooro, additional, Chi, Miaofang, additional, Lu, Gang, additional, Sasaki, Kotaro, additional, and Sun, Shouheng, additional

Published
2023
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7. A Theory-Guided X-ray Absorption Spectroscopy Approach for Identifying Active Sites in Atomically Dispersed Transition-Metal Catalysts

Author

Chen, Yizhen, primary, Rana, Rachita, additional, Sours, Tyler, additional, Vila, Fernando D., additional, Cao, Shaohong, additional, Blum, Thomas, additional, Hong, Jiyun, additional, Hoffman, Adam S., additional, Fang, Chia-Yu, additional, Huang, Zhennan, additional, Shang, Chunyan, additional, Wang, Chuanhao, additional, Zeng, Jie, additional, Chi, Miaofang, additional, Kronawitter, Coleman X., additional, Bare, Simon R., additional, Gates, Bruce C., additional, and Kulkarni, Ambarish R., additional

Published
2021
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9. Kinetically Controlled Synthesis of Pd–Cu Janus Nanocrystals with Enriched Surface Structures and Enhanced Catalytic Activities toward CO2 Reduction

Author

Lyu, Zhiheng, primary, Zhu, Shangqian, additional, Xu, Lang, additional, Chen, Zitao, additional, Zhang, Yu, additional, Xie, Minghao, additional, Li, Tiehuai, additional, Zhou, Shan, additional, Liu, Jingyue, additional, Chi, Miaofang, additional, Shao, Minhua, additional, Mavrikakis, Manos, additional, and Xia, Younan, additional

Published
2020
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10. Anisotropic Strain Tuning of L10 Ternary Nanoparticles for Oxygen Reduction

Author

Li, Junrui, primary, Sharma, Shubham, additional, Wei, Kecheng, additional, Chen, Zitao, additional, Morris, David, additional, Lin, Honghong, additional, Zeng, Cheng, additional, Chi, Miaofang, additional, Yin, Zhouyang, additional, Muzzio, Michelle, additional, Shen, Mengqi, additional, Zhang, Peng, additional, Peterson, Andrew A., additional, and Sun, Shouheng, additional

Published
2020
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14. Kinetically Controlled Synthesis of Pd–Cu Janus Nanocrystals with Enriched Surface Structures and Enhanced Catalytic Activities toward CO2Reduction

Author

Lyu, Zhiheng, Zhu, Shangqian, Xu, Lang, Chen, Zitao, Zhang, Yu, Xie, Minghao, Li, Tiehuai, Zhou, Shan, Liu, Jingyue, Chi, Miaofang, Shao, Minhua, Mavrikakis, Manos, and Xia, Younan

Abstract

Bimetallic nanocrystals often outperform their monometallic counterparts in catalysis as a result of the electronic coupling and geometric effect arising from two different metals. Here we report a facile synthesis of Pd–Cu Janus nanocrystals with controlled shapes through site-selected growth by reducing the Cu(II) precursor with glucose in the presence of hexadecylamine and Pd icosahedral seeds. Specifically, at a slow reduction rate, the Cu atoms nucleate and grow from one vertex of the icosahedral seed to form a penta-twinned Janus nanocrystal in the shape of a pentagonal bipyramid or decahedron. At a fast reduction rate, in contrast, the Cu atoms can directly nucleate from or diffuse to the edge of the icosahedral seed for the generation of a singly twinned Janus nanocrystal in the shape of a truncated bitetrahedron. The segregation of two elements and the presence of twin boundaries on the surface make the Pd–Cu Janus nanocrystals effective catalysts for the electrochemical reduction of CO2. An onset potential as low as −0.7 VRHE(RHE: reversible hydrogen electrode) was achieved for C2+products in 0.5 M KHCO3solution, together with a faradaic efficiency approaching 51.0% at −1.0 VRHE. Density functional theory and Pourbaix phase diagram studies demonstrated that the high CO coverage on the Pd sites (either metallic or hydride form) during electrocatalysis enabled the spillover of CO to the Cu sites toward subsequent C–C coupling, promoting the formation of C2+species. This work offers insights for the rational fabrication of bimetallic nanocrystals featuring desired compositions, shapes, and twin structures for catalytic applications.

Published
2021
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15. Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation

Author

Zhan, Wangcheng, primary, Wang, Jinglin, additional, Wang, Haifeng, additional, Zhang, Jinshui, additional, Liu, Xiaofei, additional, Zhang, Pengfei, additional, Chi, Miaofang, additional, Guo, Yanglong, additional, Guo, Yun, additional, Lu, Guanzhong, additional, Sun, Shouheng, additional, Dai, Sheng, additional, and Zhu, Huiyuan, additional

Published
2017
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16. Anisotropic Strain Tuning of L10Ternary Nanoparticles for Oxygen Reduction

Author

Li, Junrui, Sharma, Shubham, Wei, Kecheng, Chen, Zitao, Morris, David, Lin, Honghong, Zeng, Cheng, Chi, Miaofang, Yin, Zhouyang, Muzzio, Michelle, Shen, Mengqi, Zhang, Peng, Peterson, Andrew A., and Sun, Shouheng

Abstract

Tuning the performance of nanoparticle (NP) catalysts by controlling the NP surface strain has evolved as an important strategy to optimize NP catalysis in many energy conversion reactions. Here, we present our new study on using an eigenforce model to predict and experiments to verify the strain-induced catalysis enhancement of the oxygen reduction reaction (ORR) in the presence of L10-CoMPt NPs (M = Mn, Fe, Ni, Cu, Ni). The eigenforce model allowed us to predict anisotropic (that is, two-dimensional) strain levels on distorted Pt(111) surfaces. Experimentally, by preparing a series of 5 nm L10-CoMPt NPs, we could push the ORR catalytic activity of these NPs toward the optimum region of the theoretical two-dimensional volcano plot predicted for L10-CoMPt. The best ORR catalyst in the alloy NP series we studied is L10-CoNiPt, which has a mass activity of 3.1 A/mgPtand a specific activity of 9.3 mA/cm2at room temperature with only 15.9% loss of mass activity after 30 000 cycles at 60 °C in 0.1 M HClO4.

Published
2020
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18. Pd@Pt Core–Shell Concave Decahedra: A Class of Catalysts for the Oxygen Reduction Reaction with Enhanced Activity and Durability

Author

Wang, Xue, primary, Vara, Madeline, additional, Luo, Ming, additional, Huang, Hongwen, additional, Ruditskiy, Aleksey, additional, Park, Jinho, additional, Bao, Shixiong, additional, Liu, Jingyue, additional, Howe, Jane, additional, Chi, Miaofang, additional, Xie, Zhaoxiong, additional, and Xia, Younan, additional

Published
2015
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22. Design and Synthesis of Bimetallic Electrocatalyst with Multilayered Pt-Skin Surfaces

Author

Wang, Chao, primary, Chi, Miaofang, additional, Li, Dongguo, additional, Strmcnik, Dusan, additional, van der Vliet, Dennis, additional, Wang, Guofeng, additional, Komanicky, Vladimir, additional, Chang, Kee-Chul, additional, Paulikas, Arvydas P., additional, Tripkovic, Dusan, additional, Pearson, John, additional, More, Karren L., additional, Markovic, Nenad M., additional, and Stamenkovic, Vojislav R., additional

Published
2011
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25. Solution-Phase Synthesis of PdH0.706Nanocubes with Enhanced Stability and Activity toward Formic Acid Oxidation

Author

Shi, Yifeng, Schimmenti, Roberto, Zhu, Shangqian, Venkatraman, Kartik, Chen, Ruhui, Chi, Miaofang, Shao, Minhua, Mavrikakis, Manos, and Xia, Younan

Abstract

Palladium is one of the few metals capable of forming hydrides, with the catalytic properties being dependent on the elemental composition and spatial distribution of H atoms in the lattice. Herein, we report a facile method for the complete transformation of Pd nanocubes into a stable phase made of PdH0.706by treating them with aqueous hydrazine at a concentration as low as 9.2 mM. Using formic acid oxidation (FAO) as a model reaction, we systematically investigated the structure–catalytic property relationship of the resultant nanocubes with different degrees of hydride formation. The current density at 0.4 V was enhanced by four times when the nanocubes were completely converted from Pd to PdH0.706. On the basis of a set of slab models with PdH(100) overlayers on Pd(100), we conducted density functional theory calculations to demonstrate that the degree of hybrid formation could influence both the activity and selectivity toward FAO by modulating the relative stability of formate (HCOO) and carboxyl (COOH) intermediates. This work provides a viable strategy for augmenting the performance of Pd-based catalysts toward various reactions without altering the loading of this scarce metal.

Published
2022
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26. Solution-Phase Synthesis of PdH 0.706 Nanocubes with Enhanced Stability and Activity toward Formic Acid Oxidation.

Author

Shi Y, Schimmenti R, Zhu S, Venkatraman K, Chen R, Chi M, Shao M, Mavrikakis M, and Xia Y

Abstract

Palladium is one of the few metals capable of forming hydrides, with the catalytic properties being dependent on the elemental composition and spatial distribution of H atoms in the lattice. Herein, we report a facile method for the complete transformation of Pd nanocubes into a stable phase made of PdH 0.706 by treating them with aqueous hydrazine at a concentration as low as 9.2 mM. Using formic acid oxidation (FAO) as a model reaction, we systematically investigated the structure-catalytic property relationship of the resultant nanocubes with different degrees of hydride formation. The current density at 0.4 V was enhanced by four times when the nanocubes were completely converted from Pd to PdH 0.706 . On the basis of a set of slab models with PdH(100) overlayers on Pd(100), we conducted density functional theory calculations to demonstrate that the degree of hybrid formation could influence both the activity and selectivity toward FAO by modulating the relative stability of formate (HCOO) and carboxyl (COOH) intermediates. This work provides a viable strategy for augmenting the performance of Pd-based catalysts toward various reactions without altering the loading of this scarce metal.

Published
2022
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27. Anisotropic Strain Tuning of L1 0 Ternary Nanoparticles for Oxygen Reduction.

Author

Li J, Sharma S, Wei K, Chen Z, Morris D, Lin H, Zeng C, Chi M, Yin Z, Muzzio M, Shen M, Zhang P, Peterson AA, and Sun S

Subjects
Alloys chemistry, Catalysis, Density Functional Theory, Oxidation-Reduction, Metal Nanoparticles chemistry, Oxygen chemistry
Abstract

Tuning the performance of nanoparticle (NP) catalysts by controlling the NP surface strain has evolved as an important strategy to optimize NP catalysis in many energy conversion reactions. Here, we present our new study on using an eigenforce model to predict and experiments to verify the strain-induced catalysis enhancement of the oxygen reduction reaction (ORR) in the presence of L1 0 -CoMPt NPs (M = Mn, Fe, Ni, Cu, Ni). The eigenforce model allowed us to predict anisotropic (that is, two-dimensional) strain levels on distorted Pt(111) surfaces. Experimentally, by preparing a series of 5 nm L1 0 -CoMPt NPs, we could push the ORR catalytic activity of these NPs toward the optimum region of the theoretical two-dimensional volcano plot predicted for L1 0 -CoMPt. The best ORR catalyst in the alloy NP series we studied is L1 0 -CoNiPt, which has a mass activity of 3.1 A/mg Pt and a specific activity of 9.3 mA/cm 2 at room temperature with only 15.9% loss of mass activity after 30 000 cycles at 60 °C in 0.1 M HClO 4 .

Published
2020
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