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Zan L, Amin HMA, Mostafa E, Abd-El-Latif AA, Iqbal S, Baltruschat H. Electrodeposited Cobalt Nanosheets on Smooth Silver as a Bifunctional Catalyst for OER and ORR: In Situ Structural and Catalytic Characterization. ACS APPLIED MATERIALS & INTERFACES 2022; 14:55458-55470. [PMID: 36490358 DOI: 10.1021/acsami.2c12163] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Developing earth-abundant, cost-effective, and active bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is key to boosting sustainable energy systems such as electrolyzers and lithium-air batteries. However, the performance of promising cobalt-based materials is impaired by the external effects of binders and carbon additives as well as inhomogeneous electrode fabrication. In this work, binder- and carbon-free flower-like Co-decorated Ag catalytic nanosheets were in situ-synthesized via a simple electrodeposition approach. The morphology, composition, and structure of Co/Ag before and after OER were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Co/Ag thin film electrodes with various Co contents exhibited a bifunctional activity toward ORR and OER due to a synergistic effect. XPS analysis suggested the formation of Co3O4 as the main active species for OER. In particular, Co (83%)/Ag surface revealed a 60 mV lower ORR overpotential than a pure Ag surface and even lower than drop-casted Co3O4 nanoparticles on Ag surface. Only 1.5% peroxide was generated, suggesting a four-electron transfer ORR. In addition, the OER onset potential on Co/Ag is 60 mV less than Co3O4. Tafel slopes of 71 and 75 mV dec-1 were obtained for ORR and OER, respectively. Importantly, the three-dimensional (3D) growth mechanism of a cobalt layer (∼1 nm) on a well-defined atomic smooth Ag surface is unraveled by in situ electrochemical scanning tunneling microscopy (EC-STM). EC-STM suggests that Co prefers to nucleate at the step edges of Ag and grows in a 3D, forming nanoparticles, where the deposition/dissolution process of the Co adlayer on Ag is reversible. This investigation may provide insights into design strategies of efficient oxygen electrocatalysts.
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Affiliation(s)
- Lingxing Zan
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn53117, Germany
- Key Laboratory of Chemical Reaction Engineering of Shaanxi Province, College of Chemistry & Chemical Engineering, Yan'an University, Yan'an716000, China
| | - Hatem M A Amin
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn53117, Germany
- Chemistry Department, Faculty of Science, Cairo University, Giza12613, Egypt
| | - Ehab Mostafa
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn53117, Germany
- Chemistry Department, Faculty of Science, Mansoura University, Mansoura35516, Egypt
| | - Abdelaziz A Abd-El-Latif
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn53117, Germany
- Physical Chemistry Department, National Research Center, Cairo12311, Egypt
| | - Shahid Iqbal
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn53117, Germany
| | - Helmut Baltruschat
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn53117, Germany
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Optimisation Study of Co Deposition on Chars from MAP of Waste Tyres as Green Electrodes in ORR for Alkaline Fuel Cells. ENERGIES 2020. [DOI: 10.3390/en13215646] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Oxygen Reduction Reaction (ORR) catalysts, from waste automobile tyres obtained from Microwave assisted pyrolysis (MAP), were enriched with Co and Cu using the simple treatments sonochemical and electrochemical deposition. Catalytic activity was evaluated through onset potential and number of exchanged electrons measurements. Electrochemical data demonstrate an improvement in catalytic activity of the electrochemical modified char with Co. Char electrodes enriched with Co show a maximum positive shift of 40 mV with respect to raw char electrodes with a number of exchanged electrons per O2 molecule close to 4 (as for Pt) for the best sample. This corresponds to a reduction of the production of unwanted oxygen peroxide from 23% for raw char to 1%. Sample structure evolution before and after electrochemical deposition and electro-catalysis was investigated by scanning transmission electron microscopy and XPS. Such electrochemical treatments open new possibilities of refining waste chars and finding an economic alternative to noble metals-based catalysts for alkaline fuel cells.
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Galvanic Exchange as a Novel Method for Carbon Nitride Supported CoAg Catalyst Synthesis for Oxygen Reduction and Carbon Dioxide Conversion. Catalysts 2019. [DOI: 10.3390/catal9100860] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
A bimetallic alloy of CoAg nanoparticles (NPs) on a carbon nitride (CN) surface was synthesized using a galvanic exchange process for the oxygen reduction reaction (ORR) and carbon dioxide electrocatalytic conversion. The reduction potential of cobalt is ([Co2+(aq) + 2e− → Co(s)], −0.28 eV) is smaller than that of Ag ([Ag+(aq) + e− → Ag(s)], 0.80 eV), which makes Co(0) to be easily replaceable by Ag+ ions. Initially, Co NPs (nanoparticles) were synthesized on a CN surface via adsorbing the Co2+ precursor on the surface of CN and subsequently reducing them with NaBH4 to obtain Co/CN NP. The Co NPs on the surface of CN were then subjected to galvanic exchange, where the sacrificial Co atoms were replaced by Ag atoms. As the process takes place on a solid surface, only the partial replacement of Co by Ag was possible generating CoAg/CN NPs. Synthesized CoAg/CN bimetallic alloy were characterized using different techniques such as powder x-ray diffraction (PXRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electron diffraction spectroscopy (EDS) to confirm the product. Both the catalysts, Co/CN and CoAg/CN, were evaluated for oxygen reduction reaction in 1M KOH solution and carbon dioxide conversion in 0.5 M KHCO3. In the case of ORR, the CoAg/CN was found to be an efficient electrocatalyst with the onset potential of 0.93 V, which is comparable to commercially available Pt/C having Eonset at 0.91 V. In the electrocatalytic conversion of CO2, the CoAg/CN showed better performance than Co/CN. The cathodic current decreased dramatically below −0.9V versus Ag/AgCl indicating the high conversion of CO2.
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Ashok A, Kumar A, Matin MA, Tarlochan F. Probing the effect of combustion controlled surface alloying in silver and copper towards ORR and OER in alkaline medium. J Electroanal Chem (Lausanne) 2019. [DOI: 10.1016/j.jelechem.2019.05.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Ag–Co Electrocatalysts for Rechargeable Lithium–O2 Batteries: O2 Pressure and Current Density Effects. Electrocatalysis (N Y) 2019. [DOI: 10.1007/s12678-019-00540-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Cosert KM, Reguera G. Voltammetric study of conductive planar assemblies of Geobacter nanowire pilins unmasks their ability to bind and mineralize divalent cobalt. J Ind Microbiol Biotechnol 2019; 46:1239-1249. [PMID: 30953253 DOI: 10.1007/s10295-019-02167-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/23/2019] [Indexed: 11/26/2022]
Abstract
Geobacter bacteria assemble a helical peptide of the Type IVa pilin subclass as conductive pili decorated with metal binding and reduction sites. We used recombinant techniques to synthesize thiolated pilin derivatives and self-assembled them on gold electrodes as a monolayer that concentrated the metal traps at the liquid interface. Cyclic and step potential voltammetry demonstrated the conductivity of the pilin films and their ability to bind and reductively precipitate divalent cobalt (Co2+) in a diffusion-controlled reaction characterized by fast binding kinetics, efficient charge transfer, and three-dimensional nanoparticle growth at discreet sites. Furthermore, cobalt oxidation at the pilin film was slower than on bare gold, consistent with a peptide optimized for metal immobilization. These properties make recombinant pilins attractive building blocks for the synthesis of novel biomaterials for the immobilization of toxic cationic metals that, like Co2+, are sparingly soluble and, thus, less mobile and bioavailable as reduced species.
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Affiliation(s)
- Krista M Cosert
- Department of Microbiology and Molecular Genetics, Michigan State University, 567 Wilson Rd, Rm. 6190, Biomedical and Physical Science Building, East Lansing, MI, 48824, USA
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332, USA
| | - Gemma Reguera
- Department of Microbiology and Molecular Genetics, Michigan State University, 567 Wilson Rd, Rm. 6190, Biomedical and Physical Science Building, East Lansing, MI, 48824, USA.
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Ashok A, Kumar A, Tarlochan F. Surface Alloying in Silver-Cobalt through a Second Wave Solution Combustion Synthesis Technique. NANOMATERIALS 2018; 8:nano8080604. [PMID: 30096855 PMCID: PMC6116214 DOI: 10.3390/nano8080604] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/13/2018] [Accepted: 07/20/2018] [Indexed: 11/17/2022]
Abstract
Herein, we report the synthesis of silver-cobalt nanopowders using three different modes of solution combustion synthesis, and we present the effects of the synthesis conditions on particle morphology. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV-Visible spectrophotometer (UV-vis), Transmission electron microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS) to understand the structural and elemental properties. When Co is synthesized over Ag in a second wave of combustion, peak shifts observed in XRD and XPS show a change in the cell parameters and prove the existence of a strong electronic interaction between Ag and Co. Better control of mixing and alloying through the second wave combustion synthesis mode (SWCS) was evident. The sequence of combustion affects the structure and composition of the material. SWCS reduces the amount of carbon content, as compared to single-stage combustion, and the combustion of carbon is followed by a rearrangement of atoms.
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Affiliation(s)
- Anchu Ashok
- Department of Mechanical and Industrial Engineering, College of Engineering, Qatar University, Doha P.O. Box-2713, Qatar.
| | - Anand Kumar
- Department of Chemical Engineering, College of Engineering, Qatar University, Doha P.O. Box-2713, Qatar.
| | - Faris Tarlochan
- Department of Mechanical and Industrial Engineering, College of Engineering, Qatar University, Doha P.O. Box-2713, Qatar.
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Yu A, Lee C, Lee NS, Kim MH, Lee Y. Highly Efficient Silver-Cobalt Composite Nanotube Electrocatalysts for Favorable Oxygen Reduction Reaction. ACS APPLIED MATERIALS & INTERFACES 2016; 8:32833-32841. [PMID: 27934168 DOI: 10.1021/acsami.6b11073] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This paper reports the synthesis and characterization of silver-cobalt (AgCo) bimetallic composite nanotubes. Cobalt oxide (Co3O4) nanotubes were fabricated by electrospinning and subsequent calcination in air and then reduced to cobalt (Co) metal nanotubes via further calcination under a H2/Ar atmosphere. As-prepared Co nanotubes were then employed as templates for the following galvanic replacement reaction (GRR) with silver (Ag) precursor (AgNO3), which produced AgCo composite nanotubes. Various AgCo nanotubes were readily synthesized with applying different reaction times for the reduction of Co3O4 nanotubes and GRR. One hour reduction was sufficiently long to convert Co3O4 to Co metal, and 3 h GRR was enough to deposit Ag layer on Co nanotubes. The tube morphology and copresence of Ag and Co in AgCo composite nanotubes were confirmed with SEM, HRTEM, XPS, and XRD analyses. Electroactivity of as-prepared AgCo composite nanotubes was characterized for ORR with rotating disk electrode (RDE) voltammetry. Among differently synthesized AgCo composite nanotubes, the one synthesized via 1 h reduction and 3 h GRR showed the best ORR activity (the most positive onset potential, greatest limiting current density, and highest number of electrons transferred). Furthermore, the ORR performance of the optimized AgCo composite nanotubes was superior compared to pure Co nanotubes, pure Ag nanowires, and bare platinum (Pt). High ethanol tolerance of AgCo composite nanotubes was also compared with the commercial Pt/C and then verified its excellent resistance to ethanol contamination.
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Affiliation(s)
- Areum Yu
- Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea
| | - Chongmok Lee
- Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea
| | - Nam-Suk Lee
- National Institute for Nanomaterials Technology (NINT), Pohang University of Science and Technology (POSTECH) , Pohang 37673, Korea
| | - Myung Hwa Kim
- Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea
| | - Youngmi Lee
- Department of Chemistry and Nano Science, Ewha Womans University , Seoul 03760, Korea
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Qaseem A, Chen F, Wu X, Johnston RL. Pt-free silver nanoalloy electrocatalysts for oxygen reduction reaction in alkaline media. Catal Sci Technol 2016. [DOI: 10.1039/c5cy02270c] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Silver nanoalloy electrocatalysts with comparable activity and better stability than commercial Pt/C for oxygen reduction reaction (ORR) in advanced metal–air batteries and fuel cells.
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Affiliation(s)
- Adnan Qaseem
- State Key Laboratory of Solidification Processing
- Northwestern Polytechnical University
- Xian
- China
| | - Fuyi Chen
- State Key Laboratory of Solidification Processing
- Northwestern Polytechnical University
- Xian
- China
| | - Xiaoqiang Wu
- State Key Laboratory of Solidification Processing
- Northwestern Polytechnical University
- Xian
- China
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