Editorial

3 pages, 185 KiB

Open AccessEditorial

Electrocatalysts for Energy Conversion and Storage Devices

by Vincenzo Baglio

Catalysts 2021, 11(12), 1491; https://doi.org/10.3390/catal11121491 - 06 Dec 2021

Viewed by 1863

Energy’s efficient conversion and storage are closely correlated to the development of electrochemical energy technologies, such as fuel cells, batteries, electrolyzers, etc [...] Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

Research

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13 pages, 4518 KiB

Open AccessArticle

Electrocatalysis for Oxygen Reduction Reaction on EDTAFeNa and Melamine co-Derived Self-Supported Fe-N-C Materials

by Mengfan Shen, Ziwei Meng, Tong Xue, Hongfang Shen and Xiang-Hui Yan

Catalysts 2021, 11(5), 623; https://doi.org/10.3390/catal11050623 - 12 May 2021

Cited by 2 | Viewed by 2177

Abstract

To explore high-performing alternatives to platinum-based catalysts is highly desirable for lowering costs and thus promoting fuel cell commercialization. Herein, self-supported Fe-N-C materials were prepared by the pyrolysis of dual precursors including EDTA ferric sodium (EDTAFeNa) and melamine (MA), followed by acid-leaching and [...] Read more.

To explore high-performing alternatives to platinum-based catalysts is highly desirable for lowering costs and thus promoting fuel cell commercialization. Herein, self-supported Fe-N-C materials were prepared by the pyrolysis of dual precursors including EDTA ferric sodium (EDTAFeNa) and melamine (MA), followed by acid-leaching and final annealing. Towards an oxygen reduction reaction (ORR) in 0.1 M KOH, the as-prepared MA/EDTAFeNa-HT2 delivered onset (E_onset) and half-wave (E_1/2) potentials of 0.97 and 0.84 V vs. RHE, respectively, identical with that of a state-of-the-art Pt/C catalyst, accompanied with predominantly a four-electron pathway. The introduction of MA and extension of acid-leaching promoted a positive shift of 50 mV for E_1/2 relative to that of only the EDTAFeNa-derived counterpart. It was revealed that the enhancement of ORR activity is attributed to a decrease in magnetic Fe species and increase in pyridinic/quanternary nitrogen content whilst nearly excluding effects of the graphitization degree, variety of crystalline iron species, and mesoscopic structure. The usage of dual precursors exhibited great potential for the large-scale production of inexpensive and efficient Fe-N-C materials. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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12 pages, 1409 KiB

Open AccessFeature PaperArticle

Optimization of the Catalytic Layer for Alkaline Fuel Cells Based on Fumatech Membranes and Ionomer

by David Sebastián, Giovanni Lemes, José M. Luque-Centeno, María V. Martínez-Huerta, Juan I. Pardo and María J. Lázaro

Catalysts 2020, 10(11), 1353; https://doi.org/10.3390/catal10111353 - 20 Nov 2020

Cited by 15 | Viewed by 3891

Abstract

Polymer electrolyte fuel cells with alkaline anion exchange membranes (AAEMs) have gained increasing attention because of the faster reaction kinetics associated with the alkaline environment compared to acidic media. While the development of anion exchange polymer membranes is increasing, the catalytic layer structure [...] Read more.

Polymer electrolyte fuel cells with alkaline anion exchange membranes (AAEMs) have gained increasing attention because of the faster reaction kinetics associated with the alkaline environment compared to acidic media. While the development of anion exchange polymer membranes is increasing, the catalytic layer structure and composition of electrodes is of paramount importance to maximize fuel cell performance. In this work, we examine the preparation procedures for electrodes by catalyst-coated substrate to be used with a well-known commercial AAEM, Fumasep^® FAA-3, and a commercial ionomer of the same nature (Fumion), both from Fumatech GmbH. The anion exchange procedure, the ionomer concentration in the catalytic layer and also the effect of membrane thickness, are investigated as they are very relevant parameters conditioning the cell behavior. The best power density was achieved upon ion exchange of the ionomer by submerging the electrodes in KCl (isopropyl alcohol/water solution) for at least one hour, two exchange steps, followed by treatment in KOH for 30 min. The optimum ionomer (Fumion) concentration was found to be close to 50 wt%, with a relatively narrow interval of functioning ionomer percentages. These results provide a practical guide for electrode preparation in AAEM-based fuel cell research. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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12 pages, 2076 KiB

Open AccessArticle

X-ray Absorption Spectroscopy Investigation of Platinum–Gadolinium Thin Films with Different Stoichiometry for the Oxygen Reduction Reaction

by Kim Degn Jensen, Anders Filsøe Pedersen, Eleonora Zamburlini, Ifan Erfyl Lester Stephens, Ib Chorkendorff and María Escudero-Escribano

Catalysts 2020, 10(9), 978; https://doi.org/10.3390/catal10090978 - 31 Aug 2020

Cited by 3 | Viewed by 2740

Abstract

Alloys of platinum and lanthanides present a remarkable activity for the oxygen reduction reaction—both in the form of extended surfaces and nanoparticulate catalysts. Co-sputter-deposited thin film catalysts based on platinum and gadolinium show great oxygen reduction activity improvement over pure Pt. The sputter-deposition [...] Read more.

Alloys of platinum and lanthanides present a remarkable activity for the oxygen reduction reaction—both in the form of extended surfaces and nanoparticulate catalysts. Co-sputter-deposited thin film catalysts based on platinum and gadolinium show great oxygen reduction activity improvement over pure Pt. The sputter-deposition technique represents a viable and versatile approach for investigating model catalyst systems with different compositions. In this work, co-sputtered Pt₅Gd and Pt_7.5Gd thin films were investigated using X-ray absorption spectroscopy as well as standardized electrochemical techniques. These investigations revealed the importance of forming alloys with specific stoichiometry, supporting the need of forming compressively strained Pt overlayers in order to achieve optimum catalytic performances. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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18 pages, 3268 KiB

Open AccessFeature PaperArticle

Low-Noble-Metal-Loading Hybrid Catalytic System for Oxygen Reduction Utilizing Reduced-Graphene-Oxide-Supported Platinum Aligned with Carbon-Nanotube-Supported Iridium

by Beata Dembinska, Agnieszka Zlotorowicz, Magdalena Modzelewska, Krzysztof Miecznikowski, Iwona A. Rutkowska, Leszek Stobinski, Artur Malolepszy, Maciej Krzywiecki, Jerzy Zak, Enrico Negro, Vito Di Noto and Pawel J. Kulesza

Catalysts 2020, 10(6), 689; https://doi.org/10.3390/catal10060689 - 19 Jun 2020

Cited by 8 | Viewed by 2977

Abstract

Hybrid systems composed of the reduced graphene oxide-supported platinum and multiwalled carbon nanotube-supported iridium (both noble metals utilized at low loadings on the level of 15 and ≤2 µg cm⁻², respectively) were considered as catalytic materials for the reduction of oxygen [...] Read more.

Hybrid systems composed of the reduced graphene oxide-supported platinum and multiwalled carbon nanotube-supported iridium (both noble metals utilized at low loadings on the level of 15 and ≤2 µg cm⁻², respectively) were considered as catalytic materials for the reduction of oxygen in acid media (0.5-mol dm⁻³ H₂SO₄). The electrocatalytic activity toward reduction of oxygen and formation of hydrogen peroxide intermediate are tested using rotating ring–disk electrode (RRDE) voltammetric experiments. The efficiency of the proposed catalytic systems was also addressed by performing galvanodynamic measurements with gas diffusion electrode (GDE) half-cell at 80 °C. The role of carbon nanotubes is to improve charge distribution at the electrocatalytic interface and facilitate the transport of oxygen and electrolyte in the catalytic systems by lowering the extent of reduced graphene oxide restacking during solvent evaporation. The diagnostic electrochemical experiments revealed that—in iridium-containing systems—not only higher disk currents, but also somehow smaller ring currents are produced (when compared to the Ir-free reduced graphene oxide-supported platinum), clearly implying formation of lower amounts of the undesirable hydrogen peroxide intermediate. The enhancement effect originating from the addition of traces of iridium (supported onto carbon nanotubes) to platinum, utilized at low loading, may originate from high ability of iridium to induce decomposition of the undesirable hydrogen peroxide intermediate. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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17 pages, 3468 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Enhanced Photoelectrochemical Water Splitting at Hematite Photoanodes by Effect of a NiFe-Oxide co-Catalyst

by Carmelo Lo Vecchio, Stefano Trocino, Sabrina Campagna Zignani, Vincenzo Baglio, Alessandra Carbone, María Isabel Díez García, Maxime Contreras, Roberto Gómez and Antonino Salvatore Aricò

Catalysts 2020, 10(5), 525; https://doi.org/10.3390/catal10050525 - 09 May 2020

Cited by 14 | Viewed by 3538

Abstract

Tandem photoelectrochemical cells (PECs), made up of a solid electrolyte membrane between two low-cost photoelectrodes, were investigated to produce “green” hydrogen by exploiting renewable solar energy. The assembly of the PEC consisted of an anionic solid polymer electrolyte membrane (gas separator) clamped between [...] Read more.

Tandem photoelectrochemical cells (PECs), made up of a solid electrolyte membrane between two low-cost photoelectrodes, were investigated to produce “green” hydrogen by exploiting renewable solar energy. The assembly of the PEC consisted of an anionic solid polymer electrolyte membrane (gas separator) clamped between an n-type Fe₂O₃ photoanode and a p-type CuO photocathode. The semiconductors were deposited on fluorine-doped tin oxide (FTO) transparent substrates and the cell was investigated with the hematite surface directly exposed to a solar simulator. Ionomer dispersions obtained from the dissolution of commercial polymers in the appropriate solvents were employed as an ionic interface with the photoelectrodes. Thus, the overall photoelectrochemical water splitting occurred in two membrane-separated compartments, i.e., the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. A cost-effective NiFeOx co-catalyst was deposited on the hematite photoanode surface and investigated as a surface catalytic enhancer in order to improve the OER kinetics, this reaction being the rate-determining step of the entire process. The co-catalyst was compared with other well-known OER electrocatalysts such as La_0.6Sr_0.4Fe_0.8CoO₃ (LSFCO) perovskite and IrRuOx. The Ni-Fe oxide was the most promising co-catalyst for the oxygen evolution in the anionic environment in terms of an enhanced PEC photocurrent and efficiency. The materials were physico-chemically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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10 pages, 2580 KiB

Open AccessArticle

Activated Carbon/MnO₂ Composites as Electrode for High Performance Supercapacitors

by Jang Rak Choi, Ji Won Lee, Guijun Yang, Young-Jung Heo and Soo-Jin Park

Catalysts 2020, 10(2), 256; https://doi.org/10.3390/catal10020256 - 20 Feb 2020

Cited by 29 | Viewed by 5707

Abstract

Activated carbon (AC) was synthesized with various weight ratios of manganese dioxide (MO) through a simple hydrothermal approach. The electrochemical performance of the synthesized activated carbon/MnO₂ composites was investigated. The effect of the activated carbon/MnO₂ (AM) ratio on the electrochemical properties [...] Read more.

Activated carbon (AC) was synthesized with various weight ratios of manganese dioxide (MO) through a simple hydrothermal approach. The electrochemical performance of the synthesized activated carbon/MnO₂ composites was investigated. The effect of the activated carbon/MnO₂ (AM) ratio on the electrochemical properties of the activated carbon/MnO₂ composites and the pore structure was also examined. The results show that the specific capacitance of the activated carbon material has been improved after the addition of MO. The as-synthesized composite material exhibits specific capacitance of 60.3 F g⁻¹ at 1 A g⁻¹, as well as stable cycle performance and 99.6% capacitance retention over 5000 cycles. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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12 pages, 2885 KiB

Open AccessArticle

Study of the Hydrogen Evolution Reaction Using Ionic Liquid/Cobalt Porphyrin Systems as Electro and Photoelectrocatalysts

by Leyla Gidi, Jessica Honores, José Ibarra, Roxana Arce, M. J Aguirre and Galo Ramírez

Catalysts 2020, 10(2), 239; https://doi.org/10.3390/catal10020239 - 17 Feb 2020

Cited by 9 | Viewed by 2686

Abstract

In this work, the design and manufacture of graphite paste (Gr) electrodes is carried out, including N-octylpyridinium hexafluorophosphate (OPyPF₆) ionic liquid (IL) as binder and modification with Co-octaethylporphyrin (Co), in order to study the hydrogen evolution reaction (HER) in the [...] Read more.

In this work, the design and manufacture of graphite paste (Gr) electrodes is carried out, including N-octylpyridinium hexafluorophosphate (OPyPF₆) ionic liquid (IL) as binder and modification with Co-octaethylporphyrin (Co), in order to study the hydrogen evolution reaction (HER) in the absence and presence of light. The system is characterized by XRD and FESEM-EDX (Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy), confirming the presence of all the components of the system in the electrode surface. The studies carried out in this investigation confirm that a photoelectrocatalytic system towards HER is obtained. The system is stable, efficient and easy to prepare. Through cyclic voltammetry and electrochemical impedance spectroscopy, was determined that these electrodes improve their electrochemical and electrical properties upon the addition of OPyPF₆. These effects improve even more when the systems are modified with Co porphyrin. It is also observed that when the systems are irradiated at 395 nm, the redox process is favored in energy terms, as well as in its electrical properties. Through gas chromatography, it was determined that the graphite paste electrode in the presence of ionic liquid and porphyrin (Gr/IL/Co) presents a high turnover number (TON) value (6342 and 6827 in presence of light) in comparison to similar systems reported. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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12 pages, 3565 KiB

Open AccessArticle

A Zn-Doped Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ Perovskite Cathode with Enhanced ORR Catalytic Activity for SOFCs

by Qiannan Zeng, Xiaozhen Zhang, Wei Wang, Dandan Zhang, Yuhua Jiang, Xiaojian Zhou and Bin Lin

Catalysts 2020, 10(2), 235; https://doi.org/10.3390/catal10020235 - 15 Feb 2020

Cited by 40 | Viewed by 3608

Abstract

The insufficient oxygen reduction reaction activity of cathode materials is one of the main obstacles to decreasing the operating temperature of solid oxide fuel cells (SOFCs). Here, we report a Zn-doped perovskite oxide Ba_0.5Sr_0.5(Co_0.8Fe_0.2)_0.96 [...] Read more.

The insufficient oxygen reduction reaction activity of cathode materials is one of the main obstacles to decreasing the operating temperature of solid oxide fuel cells (SOFCs). Here, we report a Zn-doped perovskite oxide Ba_0.5Sr_0.5(Co_0.8Fe_0.2)_0.96Zn_0.04O_3-δ (BSCFZ) as the SOFC cathode, which exhibits much higher electrocatalytical activity than Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) for the oxygen reduction reaction (ORR). The BSCFZ cathode exhibited a polarization resistance of only 0.23 and 0.03 Ω·cm² on a symmetrical cell at 600 and 750 °C, respectively. The corresponding maximum power density of 0.58 W·cm⁻² was obtained in the yittria-stabilized zirconia (YSZ)-based anode-supported single cell at 750 °C, an increase by 35% in comparison to the BSCF cathode. The enhanced performance can be attributed to a better balance of oxygen vacancies, surface electron transfer and ionic mobility as promoted by the low valence Zn²⁺ doping. This work proves that Zn-doping is a highly effective strategy to further enhance the ORR electrocatalytic activity of state-of-the-art Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ cathode material for intermediate temperature SOFCs. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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10 pages, 2813 KiB

Open AccessArticle

Performance Improvement in Direct Methanol Fuel Cells by Using CaTiO_3-δ Additive at the Cathode

by Lucia Mazzapioda, Carmelo Lo Vecchio, Antonino Salvatore Aricò, Maria Assunta Navarra and Vincenzo Baglio

Catalysts 2019, 9(12), 1017; https://doi.org/10.3390/catal9121017 - 02 Dec 2019

Cited by 8 | Viewed by 2985

Abstract

A non-stoichiometric calcium titanate CaTiO_3-δ (CTO) was synthesized and used as oxygen reduction reaction co-catalyst (together with Pt/C) in direct methanol fuel cells (DMFCs). A membrane-electrode assembly (MEA), equipped with a composite cathode formulation (Pt/C:CTO1:1), was investigated in DMFC, using a 2 [...] Read more.

A non-stoichiometric calcium titanate CaTiO_3-δ (CTO) was synthesized and used as oxygen reduction reaction co-catalyst (together with Pt/C) in direct methanol fuel cells (DMFCs). A membrane-electrode assembly (MEA), equipped with a composite cathode formulation (Pt/C:CTO1:1), was investigated in DMFC, using a 2 M methanol solution at the anode and oxygen at the cathode, and compared with an MEA equipped with a benchmark Pt/C cathode catalyst. It appears that the presence of the CTO additive promotes the oxygen reduction reaction (ORR) due to the presence of oxygen vacancies as available active sites for oxygen adsorption in the lattice. The increase in power density obtained with the CTO-based electrode, compared with the benchmark Pt/C, was more than 40% at 90 °C, reaching a maximum power density close to 120 mW cm⁻², which is one of the highest values reported in the literature under similar operating conditions. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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12 pages, 2429 KiB

Open AccessArticle

In-situ Quantification of Nanoparticles Oxidation: A Fixed Energy X-ray Absorption Approach

by Enrico Berretti, Andrea Giaccherini, Giordano Montegrossi, Francesco D’Acapito, Francesco Di Benedetto, Claudio Zafferoni, Alessandro Puri, Giovanni Orazio Lepore, Hamish Miller, Walter Giurlani, Massimo Innocenti, Francesco Vizza and Alessandro Lavacchi

Catalysts 2019, 9(8), 659; https://doi.org/10.3390/catal9080659 - 31 Jul 2019

Cited by 8 | Viewed by 3584

Abstract

The oxidation of palladium nanoparticles causes the performance degradation of alkaline direct ethanol fuel cells. Quantifying this oxidation is a task of tremendous importance to design mitigation strategies that extend the service life of catalysts and devices. Here, we show that the Fixed [...] Read more.

The oxidation of palladium nanoparticles causes the performance degradation of alkaline direct ethanol fuel cells. Quantifying this oxidation is a task of tremendous importance to design mitigation strategies that extend the service life of catalysts and devices. Here, we show that the Fixed Energy X-ray Absorption Voltammetry (FEXRAV) can provide this information with an in-situ approach. To do so, we have developed a quantification method that assumes the linear response at fixed energy. With this method, we have investigated the oxidation of carbon black-supported palladium electrocatalysts during cyclic voltammetry in the same solution employed as a fuel in the direct ethanol fuel cells. We have shown that up to 38% of the palladium is oxidised at 1.2 V vs. RHE and that such oxidation also happens at lower potentials that the catalyst can experience in real direct ethanol fuel cells. The result of this study is a proof of concept of quantitative FEXRAV. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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10 pages, 2653 KiB

Open AccessArticle

Point-Defect-Rich Carbon Sheets as the High-Activity Catalyst Toward Oxygen Reduction and Hydrogen Evolution

by Wenjing Yuan, Fuhua Zhang, Yaoyao Wu, Xiaotao Chen, Chihhsiang Fang and Chuanhao Li

Catalysts 2019, 9(4), 386; https://doi.org/10.3390/catal9040386 - 25 Apr 2019

Cited by 8 | Viewed by 3129

Abstract

Exploring a novel approach for the synthesis of oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) catalysts with inexpensive and high-activity is desirable. Herein, we report a bubble templating method to synthesize the graphene-like mesoporous carbon sheets with point defects as ORR/HER [...] Read more.

Exploring a novel approach for the synthesis of oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) catalysts with inexpensive and high-activity is desirable. Herein, we report a bubble templating method to synthesize the graphene-like mesoporous carbon sheets with point defects as ORR/HER bifunctional electrocatalysts. The typical product shows excellent ORR performance including the positive onset potential (740 mV) and high diffusion-limiting current density (4.07 mA cm⁻²). Along with small Tafel slopes, the overpotential is determined to be about −453 and −378 mV at 10 mA cm⁻² in both alkaline and acidic media, which suggests a good candidate for HER reaction as well. The superior catalytic activities are derived from the abundant point defects on the mesoporous carbon sheets surface, especially the existence of pyridinic and pyrrolic nitrogen species. This study may be an alternative route to prepare the novel functional materials for the applications of ORR and HER. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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15 pages, 6088 KiB

Open AccessArticle

Pt/C and Pt/SnO_x/C Catalysts for Ethanol Electrooxidation: Rotating Disk Electrode Study

by Artem S. Pushkarev, Irina V. Pushkareva, Natalia A. Ivanova, Stephanus P. du Preez, Dmitri Bessarabov, Ratibor G. Chumakov, Vladimir G. Stankevich, Vladimir N. Fateev, Anatoly A. Evdokimov and Sergey A. Grigoriev

Catalysts 2019, 9(3), 271; https://doi.org/10.3390/catal9030271 - 16 Mar 2019

Cited by 33 | Viewed by 4815

Abstract

Pt/C and Pt/SnO_x/C catalysts were synthesized using the polyol method. Their structure, morphology and chemical composition were studied using a scanning electron microscope equipped with an energy dispersive X-ray spectrometer, transition electron microscope and X-ray photoelectron spectroscope. Electrochemical measurements were based [...] Read more.

Pt/C and Pt/SnO_x/C catalysts were synthesized using the polyol method. Their structure, morphology and chemical composition were studied using a scanning electron microscope equipped with an energy dispersive X-ray spectrometer, transition electron microscope and X-ray photoelectron spectroscope. Electrochemical measurements were based on the results of rotating disk electrode (RDE) experiments applied to ethanol electrooxidation. The quick evaluation of catalyst activity, electrochemical behavior, and an average number of transferred electrons were made using the RDE technique. The usage of SnO_x (through the carbon support modification) in a binary system together with Pt causes a significant increase of the catalyst activity in ethanol oxidation reaction and the utilization of ethanol. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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14 pages, 3883 KiB

Open AccessArticle

Comparative Study between Pristine Ag and Ag Foam for Electrochemical Synthesis of Syngas with Carbon Dioxide and Water

by Yan Yu, Na Zhong, Jinhui Fang, Shasha Tang, Xincheng Ye, Zhiqiao He and Shuang Song

Catalysts 2019, 9(1), 57; https://doi.org/10.3390/catal9010057 - 08 Jan 2019

Cited by 13 | Viewed by 3534

Abstract

The electrosynthesis of syngas (H₂ + CO) from CO₂ and H₂O can reduce greenhouse gas emissions and address the energy crisis. In the present work, silver (Ag) foam was employed as a catalytic electrode for the electrochemical reduction of [...] Read more.

The electrosynthesis of syngas (H₂ + CO) from CO₂ and H₂O can reduce greenhouse gas emissions and address the energy crisis. In the present work, silver (Ag) foam was employed as a catalytic electrode for the electrochemical reduction of CO₂ in aqueous solution to design different syngas ratios (H₂:CO). In addition to H₂ and CO, a small amount of formic acid was found in the liquid phase. By contrast, the planar polycrystalline Ag yields CO, formic acid, methane and methanol as the carbon-containing products. During the potential-controlled electrolysis, the Ag foam displayed a relatively higher activity and selectivity in the electroreduction of aqueous CO₂ to CO compared with its smooth surface counterpart, as evidenced by the lower onset potential, higher partial current density and Faradic efficiency at the same bias voltage. Moreover, the electrode remained stable after three successive cycles. Based on the characterization using X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, potential step determination and density functional theory calculations, superior performance was credited to the three-dimensional structure of Ag foam constructed with coral-like Ag particles, in which the numerous edge sites are beneficial for the stabilization of the surface adsorbed COOH species and the exposed {111} facets favor the desorption of adsorbed CO species. Full article

(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)

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