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El-Nagar GA, Yang F, Stojkovikj S, Mebs S, Gupta S, Ahmet IY, Dau H, Mayer MT. Comparative Spectroscopic Study Revealing Why the CO 2 Electroreduction Selectivity Switches from CO to HCOO - at Cu-Sn- and Cu-In-Based Catalysts. ACS Catal 2022; 12:15576-15589. [PMID: 36590316 PMCID: PMC9793466 DOI: 10.1021/acscatal.2c04419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/17/2022] [Indexed: 12/12/2022]
Abstract
To address the challenge of selectivity toward single products in Cu-catalyzed electrochemical CO2 reduction, one strategy is to incorporate a second metal with the goal of tuning catalytic activity via synergy effects. In particular, catalysts based on Cu modified with post-transition metals (Sn or In) are known to reduce CO2 selectively to either CO or HCOO- depending on their composition. However, it remains unclear exactly which factors induce this switch in reaction pathways and whether these two related bimetal combinations follow similar general structure-activity trends. To investigate these questions systematically, Cu-In and Cu-Sn bimetallic catalysts were synthesized across a range of composition ratios and studied in detail. Compositional and morphological control was achieved via a simple electrochemical synthesis approach. A combination of operando and quasi-in situ spectroscopic techniques, including X-ray photoelectron, X-ray absorption, and Raman spectroscopy, was used to observe the dynamic behaviors of the catalysts' surface structure, composition, speciation, and local environment during CO2 electrolysis. The two systems exhibited similar selectivity dependency on their surface composition. Cu-rich catalysts produce mainly CO, while Cu-poor catalysts were found to mainly produce HCOO-. Despite these similarities, the speciation of Sn and In at the surface differed from each other and was found to be strongly dependent on the applied potential and the catalyst composition. For Cu-rich compositions optimized for CO production (Cu85In15 and Cu85Sn15), indium was present predominantly in the reduced metallic form (In0), whereas tin mainly existed as an oxidized species (Sn2/4+). Meanwhile, for the HCOO--selective compositions (Cu25In75 and Cu40Sn60), the indium exclusively exhibited In0 regardless of the applied potential, while the tin was reduced to metallic (Sn0) only at the most negative applied potential, which corresponds to the best HCOO- selectivity. Furthermore, while Cu40Sn60 enhances HCOO- selectivity by inhibiting H2 evolution, Cu25In75 improves the HCOO- selectivity at the expense of CO production. Due to these differences, we contend that identical mechanisms cannot be used to explain the behavior of these two bimetallic systems (Cu-In and Cu-Sn). Operando surface-enhanced Raman spectroscopy measurements provide direct evidence of the local alkalization and its impact on the dynamic transformation of oxidized Cu surface species (Cu2O/CuO) into a mixture of Cu(OH)2 and basic Cu carbonates [Cux(OH)y(CO3)y] rather than metallic Cu under CO2 electrolysis. This study provides unique insights into the origin of the switch in selectivity between CO and HCOO- pathways at Cu bimetallic catalysts and the nature of surface-active sites and key intermediates for both pathways.
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Affiliation(s)
- Gumaa A. El-Nagar
- Young
Investigator Group Electrochemical Conversion of CO2, Helmholtz-Zentrum Berlin für Materialien und
Energie GmbH, Hahn-Meitner-Platz 1, Berlin 14109, Germany,Department
of Chemistry, Faculty of Science, Cairo
University, Giza 12613, Egypt,
| | - Fan Yang
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Sasho Stojkovikj
- Young
Investigator Group Electrochemical Conversion of CO2, Helmholtz-Zentrum Berlin für Materialien und
Energie GmbH, Hahn-Meitner-Platz 1, Berlin 14109, Germany,Institut
für Chemie und Biochemie, Freie Universität
Berlin, Arnimallee 22, Berlin D-14195, Germany
| | - Stefan Mebs
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Siddharth Gupta
- Young
Investigator Group Electrochemical Conversion of CO2, Helmholtz-Zentrum Berlin für Materialien und
Energie GmbH, Hahn-Meitner-Platz 1, Berlin 14109, Germany,Institut
für Chemie und Biochemie, Freie Universität
Berlin, Arnimallee 22, Berlin D-14195, Germany
| | - Ibbi Y. Ahmet
- Institute
for Solar Fuels, Helmholtz-Zentrum Berlin
für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, Berlin 14109, Germany
| | - Holger Dau
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Matthew T. Mayer
- Young
Investigator Group Electrochemical Conversion of CO2, Helmholtz-Zentrum Berlin für Materialien und
Energie GmbH, Hahn-Meitner-Platz 1, Berlin 14109, Germany,Institut
für Chemie und Biochemie, Freie Universität
Berlin, Arnimallee 22, Berlin D-14195, Germany,
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Hossain UH, Jantsen G, Muench F, Kunz U, Ensinger W. Increasing the structural and compositional diversity of ion-track templated 1D nanostructures through multistep etching, plastic deformation, and deposition. NANOTECHNOLOGY 2022; 33:245603. [PMID: 35235910 DOI: 10.1088/1361-6528/ac59e5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
Ion-track etching represents a highly versatile way of introducing artificial pores with diameters down into the nm-regime into polymers, which offers considerable synthetic flexibility in template-assisted nanofabrication schemes. While the mechanistic foundations of ion-track technology are well understood, its potential for creating structurally and compositionally complex nano-architectures is far from being fully tapped. In this study, we showcase different strategies to expand the synthetic repertoire of ion-track membrane templating by creating several new 1D nanostructures, namely metal nanotubes of elliptical cross-section, funnel-shaped nanotubes optionally overcoated with titania or nickel nanospike layers, and concentrical as well as stacked metal nanotube-nanowire heterostructures. These nano-architectures are obtained solely by applying different wet-chemical deposition methods (electroless plating, electrodeposition, and chemical bath deposition) to ion-track etched polycarbonate templates, whose pore geometry is modified through plastic deformation, consecutive etching steps under differing conditions, and etching steps intermitted by spatially confined deposition, providing new motifs for nanoscale replication.
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Affiliation(s)
- U H Hossain
- Technische Universität Darmstadt, Department of Materials Science, Materials Analysis, Alarich-Weiss-Str.2, D-64287 Darmstadt, Germany
| | - G Jantsen
- Technische Universität Darmstadt, Department of Materials Science, Materials Analysis, Alarich-Weiss-Str.2, D-64287 Darmstadt, Germany
| | - F Muench
- Technische Universität Darmstadt, Department of Materials Science, Materials Analysis, Alarich-Weiss-Str.2, D-64287 Darmstadt, Germany
| | - U Kunz
- Technische Universität Darmstadt, Department of Materials Science, Materials Analysis, Alarich-Weiss-Str.2, D-64287 Darmstadt, Germany
| | - W Ensinger
- Technische Universität Darmstadt, Department of Materials Science, Materials Analysis, Alarich-Weiss-Str.2, D-64287 Darmstadt, Germany
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3
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Du G, Chen Q, Jin H, Xie S, Kuang Q, Xie Z. Concave nano-octahedral alloys: wet chemical synthesis of bimetallic Pt-Pd nanocrystals with high-index { hhl} Facets. Dalton Trans 2021; 50:12083-12087. [PMID: 34519755 DOI: 10.1039/d1dt02305e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Concave morphologies provide noble metal nanocrystals (NCs) with unique performances due to large specific surface areas, high curves, hot spots, and elevated energy facets. As a result, concave morphologies have attracted considerable attention in many areas. However, most NCs with concave shapes are currently made of a single metal, leaving plenty of room for easy wet chemical synthesis and structural analysis of unique concave structures, especially bimetallic compounds. In this work, concave octahedral Pt-Pd alloy NCs with high-index {hhl} faces were synthesized using glycine as a coordination molecule and polyvinylpyrrolidone as the surfactant and reducing agent. The high-index facets coupled with the synergistic and electronic effects between Pt and Pd provided concave octahedral Pt-Pd alloy NCs with excellent activity and stability toward the electrooxidation of formic acid when compared to their convex counterparts and commercial Pt black.
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Affiliation(s)
- Guifen Du
- Instrumental Analysis Center, Huaqiao University, Xiammen 361021, Fujian, China.,State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
| | - Qiaoli Chen
- College of Chemical Engineering and State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014, Zhejiang, China
| | - Hui Jin
- College of Chemical Engineering and State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014, Zhejiang, China
| | - Shuifen Xie
- College of Materials Science and Engineering, Huaqiao University, Xiammen 361021, Fujian, China
| | - Qin Kuang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
| | - Zhaoxiong Xie
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
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4
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Affiliation(s)
- Falk Muench
- Department of Materials and Earth Sciences Technical University of Darmstadt Alarich-Weiss-Straße 2 64287 Darmstadt Germany
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Amin KM, Muench F, Kunz U, Ensinger W. 3D NiCo-Layered double Hydroxide@Ni nanotube networks as integrated free-standing electrodes for nonenzymatic glucose sensing. J Colloid Interface Sci 2021; 591:384-395. [PMID: 33631526 DOI: 10.1016/j.jcis.2021.02.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 02/02/2021] [Accepted: 02/07/2021] [Indexed: 12/29/2022]
Abstract
Nickel cobalt layered double hydroxide (NiCo-LDH)-based materials have recently emerged as catalysts for important electrochemical applications. However, they frequently suffer from low electrical conductivity and agglomeration, which in turn impairs their performance. Herein, we present a catalyst design based on integrated, self-supported nickel nanotube networks (Ni-NTNWs) loaded with NiCo-LDH nanosheets, which represents a binder-free, hierarchically nanostructured electrode architecture combining continuous conduction paths and openly accessible macropores of low tortuosity with an ultrahigh density of active sites. Similar to macroscale metallic foams, the NTNWs serve as three-dimensionally interconnected, robust frameworks for the deposition of active material, but are structured in the submicron range. Our synthesis is solely based on scalable approaches, namely templating with commercial track-etched membranes, electroless plating, and electrodeposition. Morphological and compositional characterization proved the successful decoration of the inner and outer nanotube surfaces with a conformal NiCo-LDH layer. Ni-NTNW electrodes and hydroxide-decorated variants showed excellent performance in glucose sensing. The highest activity was achieved for the catalyst augmented with NiCo-LDH nanosheets, which surpassed the modification with pure Ni(OH)2. Despite its low thickness of 20 µm, the optimized catalyst layer provided an outstanding sensitivity of 4.6 mA mM-1 cm-2, a low detection limit of 0.2 µM, a fast response time of 5.3 s, high selectivity and stability, and two linear ranges covering four orders of magnitude, up to 2.5 mM analyte. As such, derivatized interconnected metal nano-networks represent a promising design paradigm for highly miniaturized yet effective catalyst electrodes and electrochemical sensors.
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Affiliation(s)
- Khaled M Amin
- Department of Materials Science, Technische Universität Darmstadt, Darmstadt 64287, Germany; Department of Polymer Chemistry, Atomic Energy Authority, Cairo 11787, Egypt.
| | - Falk Muench
- Department of Materials Science, Technische Universität Darmstadt, Darmstadt 64287, Germany
| | - Ulrike Kunz
- Department of Materials Science, Technische Universität Darmstadt, Darmstadt 64287, Germany
| | - Wolfgang Ensinger
- Department of Materials Science, Technische Universität Darmstadt, Darmstadt 64287, Germany
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6
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Stohr T, Fischer A, Muench F, Antoni M, Wollstadt S, Lohaus C, Kunz U, Clemens O, Klein A, Ensinger W. Electroless Nanoplating of Pd−Pt Alloy Nanotube Networks: Catalysts with Full Compositional Control for the Methanol Oxidation Reaction. ChemElectroChem 2020. [DOI: 10.1002/celc.201901939] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Tobias Stohr
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Angelina Fischer
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Falk Muench
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Markus Antoni
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Stephan Wollstadt
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Christian Lohaus
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Ulrike Kunz
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Oliver Clemens
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Andreas Klein
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
| | - Wolfgang Ensinger
- Department of Materials and Earth SciencesTechnische Universität Darmstadt Alarich-Weiß-Str. 2 64287 Darmstadt Germany
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