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15 pages, 1747 KiB

Open AccessFeature PaperArticle

Nanostructured Fe-N-C as Bifunctional Catalysts for Oxygen Reduction and Hydrogen Evolution

by

Williane da Silva Freitas

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Pedro Pablo Machado Pico

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Alessandra D’Epifanio

and

Barbara Mecheri

Catalysts 2021, 11(12), 1525; https://doi.org/10.3390/catal11121525 - 15 Dec 2021

Cited by 12 | Viewed by 2574

Abstract

The development of electrocatalysts for energy conversion and storage devices is of paramount importance to promote sustainable development. Among the different families of materials, catalysts based on transition metals supported on a nitrogen-containing carbon matrix have been found to be effective catalysts toward [...] Read more.

The development of electrocatalysts for energy conversion and storage devices is of paramount importance to promote sustainable development. Among the different families of materials, catalysts based on transition metals supported on a nitrogen-containing carbon matrix have been found to be effective catalysts toward oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) with high potential to replace conventional precious metal-based catalysts. In this work, we developed a facile synthesis strategy to obtain a Fe-N-C bifunctional ORR/HER catalysts, involving wet impregnation and pyrolysis steps. Iron (II) acetate and imidazole were used as iron and nitrogen sources, respectively, and functionalized carbon black pearls were used as conductive support. The bifunctional performance of the Fe-N-C catalyst toward ORR and HER was investigated by cyclic voltammetry, rotating ring disk electrode experiments, and electrochemical impedance spectroscopy in alkaline environment. ORR onset potential and half-wave potential were 0.95 V and 0.86 V, respectively, indicating a competitive performance in comparison with the commercial platinum-based catalyst. In addition, Fe-N-C had also a good HER activity, with an overpotential of 478 mV @10 mAcm⁻² and Tafel slope of 133 mVdec⁻¹, demonstrating its activity as bifunctional catalyst in energy conversion and storage devices, such as alkaline microbial fuel cell and microbial electrolysis cells. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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11 pages, 3432 KiB

Open AccessArticle

Uniform Distribution of Pd on GO-C Catalysts for Enhancing the Performance of Air Cathode Microbial Fuel Cell

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Catalysts 2021, 11(8), 888; https://doi.org/10.3390/catal11080888 - 22 Jul 2021

Cited by 8 | Viewed by 1798

Abstract

Metal, as a high-performance electrode catalyst, is a research hotspot in the construction of a high-performance microbial fuel cell (MFC). However, metal catalyst nanoparticles and their dispersed carriers are prone to aggregation, producing catalytic electrodes with inferior qualities. In this study, Pd is [...] Read more.

Metal, as a high-performance electrode catalyst, is a research hotspot in the construction of a high-performance microbial fuel cell (MFC). However, metal catalyst nanoparticles and their dispersed carriers are prone to aggregation, producing catalytic electrodes with inferior qualities. In this study, Pd is uniformly dispersed on the graphene framework supported by carbon black to form nanocomposite catalysts (Pd/GO-C catalysts). The effect of the palladium loading amount in the catalyst on the catalytic performance of the air cathode was further studied. The optimized metal loading afforded a reduced resistance and improved accessibility of Pd particles for the ORR. The maximum current output of the 0.250 Pd (mg/cm²) MFC was 1645 mA/m², which is 4.2-fold higher than that of the carbon paper cathode. Overall, our findings provide a novel protocol for the preparation of high-efficient ORR catalyst for MFCs. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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15 pages, 2851 KiB

Open AccessArticle

A Hybrid Microbial–Enzymatic Fuel Cell Cathode Overcomes Enzyme Inactivation Limits in Biological Fuel Cells

by

John Parker Evans

,

Dominic F. Gervasio

and

Barry M. Pryor

Catalysts 2021, 11(2), 242; https://doi.org/10.3390/catal11020242 - 11 Feb 2021

Cited by 4 | Viewed by 2192

Abstract

The construction of optimized biological fuel cells requires a cathode which combines the longevity of a microbial catalyst with the current density of an enzymatic catalyst. Laccase-secreting fungi were grown directly on the cathode of a biological fuel cell to facilitate the exchange [...] Read more.

The construction of optimized biological fuel cells requires a cathode which combines the longevity of a microbial catalyst with the current density of an enzymatic catalyst. Laccase-secreting fungi were grown directly on the cathode of a biological fuel cell to facilitate the exchange of inactive enzymes with active enzymes, with the goal of extending the lifetime of laccase cathodes. Directly incorporating the laccase-producing fungus at the cathode extends the operational lifetime of laccase cathodes while eliminating the need for frequent replenishment of the electrolyte. The hybrid microbial–enzymatic cathode addresses the issue of enzyme inactivation by using the natural ability of fungi to exchange inactive laccases at the cathode with active laccases. Finally, enzyme adsorption was increased through the use of a functionally graded coating containing an optimized ratio of titanium dioxide nanoparticles and single-walled carbon nanotubes. The hybrid microbial–enzymatic fuel cell combines the higher current density of enzymatic fuel cells with the longevity of microbial fuel cells, and demonstrates the feasibility of a self-regenerating fuel cell in which inactive laccases are continuously exchanged with active laccases. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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9 pages, 1230 KiB

Open AccessCommunication

A DFT Investigation on the Origins of Solvent-Dependent Polysulfide Reduction Mechanism in Rechargeable Li-S Batteries

by

Guan-Ying Du

,

Chi-You Liu

and

Elise Y. Li

Catalysts 2020, 10(8), 911; https://doi.org/10.3390/catal10080911 - 10 Aug 2020

Cited by 16 | Viewed by 3615

Abstract

The lithium-sulfur (Li-S) battery is one of the promising energy storage alternatives because of its high theoretical capacity and energy density. Factors governing the stability of polysulfide intermediates in Li-S batteries are complex and are strongly affected by the solvent used. Herein, the [...] Read more.

The lithium-sulfur (Li-S) battery is one of the promising energy storage alternatives because of its high theoretical capacity and energy density. Factors governing the stability of polysulfide intermediates in Li-S batteries are complex and are strongly affected by the solvent used. Herein, the polysulfide reduction and the bond cleavage reactions are calculated in different solvent environments by the density functional theory (DFT) methods. We investigate the relationship between the donor numbers (DN) as well as the dielectric constants (ε) of the solvent system and the relative stability of different polysulfide intermediates. Our results show that the polysulfide reduction mechanism is dominated by its tendency to form the ion-pair with Li⁺ in different organic solvents. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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14 pages, 4902 KiB

Open AccessArticle

Graphite–Metal Oxide Composites as Potential Anodic Catalysts for Microbial Fuel Cells

by

Elitsa Chorbadzhiyska

,

Ivo Bardarov

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Yolina Hubenova

and

Mario Mitov

Catalysts 2020, 10(7), 796; https://doi.org/10.3390/catal10070796 - 17 Jul 2020

Cited by 8 | Viewed by 2332

Abstract

In this study, graphite–metal oxide (Gr–MO) composites were produced and explored as potential anodic catalysts for microbial fuel cells. Fe₂O₃, Fe₃O₄, or Mn₃O₄ were used as a catalyst precursor. The morphology and [...] Read more.

In this study, graphite–metal oxide (Gr–MO) composites were produced and explored as potential anodic catalysts for microbial fuel cells. Fe₂O₃, Fe₃O₄, or Mn₃O₄ were used as a catalyst precursor. The morphology and structure of the fabricated materials were analyzed by scanning electron microscopy and X-ray diffraction, respectively, and their corrosion resistance was examined by linear voltammetry. The manufactured Gr–MO electrodes were tested at applied constant potential +0.2 V (vs. Ag/AgCl) in the presence of pure culture Pseudomonas putida 1046 used as a model biocatalyst. The obtained data showed that the applied poising resulted in a generation of anodic currents, which gradually increased during the long-term experiments, indicating a formation of electroactive biofilms on the electrode surfaces. All composite electrodes exhibited higher electrocatalytic activity compared to the non-modified graphite. The highest current density (ca. 100 mA.m⁻²), exceeding over eight-fold that with graphite, was achieved with Gr–Mn₃O₄. The additional analyses performed by cyclic voltammetry and electrochemical impedance spectroscopy supported the changes in the electrochemical activity and revealed substantial differences in the mechanism of current generation processes with the use of different catalysts. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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10 pages, 3805 KiB

Open AccessArticle

Study of the Effect of Activated Carbon Cathode Configuration on the Performance of a Membrane-Less Microbial Fuel Cell

by

M. L. Jiménez González

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Carlos Hernández Benítez

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Zabdiel Abisai Juarez

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Evelyn Zamudio Pérez

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Víctor Ángel Ramírez Coutiño

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Irma Robles

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Luis A. Godínez

and

Francisco J. Rodríguez-Valadez

Catalysts 2020, 10(6), 619; https://doi.org/10.3390/catal10060619 - 02 Jun 2020

Cited by 7 | Viewed by 2058

Abstract

In this paper, the effect of cathode configuration on the performance of a membrane-less microbial fuel cell (MFC) was evaluated using three different arrangements: an activated carbon bed exposed to air (MFCE), a wetland immersed in an activated carbon bed (MFCW) and a [...] Read more.

In this paper, the effect of cathode configuration on the performance of a membrane-less microbial fuel cell (MFC) was evaluated using three different arrangements: an activated carbon bed exposed to air (MFCE), a wetland immersed in an activated carbon bed (MFCW) and a cathode connected to an aeration tower featuring a water recirculation device (MFCT). To evaluate the MFC performance, the efficiency of the organic matter removal, the generated voltage, the power density and the internal resistance of the systems were properly assessed. The experimental results showed that while the COD removal efficiency was in all cases over 60% (after 40 days), the MFCT arrangement showed the best performance since the average removal value was 82%, compared to close to 70% for MFCE and MFCW. Statistical analysis of the COD removal efficiency confirmed that the performance of MCFT is substantially better than that of MFCE and MFCW. In regard to the other parameters surveyed, no significant influence of the different cathode arrangements explored could be found. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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11 pages, 1933 KiB

Open AccessArticle

Self-Nitrogen-Doped Carbon Nanosheets Modification of Anodes for Improving Microbial Fuel Cells’ Performance

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Catalysts 2020, 10(4), 381; https://doi.org/10.3390/catal10040381 - 01 Apr 2020

Cited by 6 | Viewed by 2041

Abstract

Dandelion seeds (DSs) have the advantages of high nitrogen content, low cost and easy availability and thus are ideal carbon precursors for fabricating carbon nanomaterials. Herein, this paper prepared a carbon nanosheet material by one-step carbonizing DSs with KOH activation (self-doped-nitrogen porous carbon [...] Read more.

Dandelion seeds (DSs) have the advantages of high nitrogen content, low cost and easy availability and thus are ideal carbon precursors for fabricating carbon nanomaterials. Herein, this paper prepared a carbon nanosheet material by one-step carbonizing DSs with KOH activation (self-doped-nitrogen porous carbon nanosheets (N-CNS)) and without KOH activation (unactivated self-doped-nitrogen porous carbon nanosheets (N-UA-CNS)), which could dope nitrogen atoms directly into carbon materials without additional processes. Scanning electron microscopy(SEM) images and X-ray diffraction(XRD) patterns both showed that N-CNS was of macro-porous structure, and beneficial for microorganisms’ growth. The Brunauer Emmett Teller(BET) surface area of N-CNS was 2107.5 m² g⁻¹, which was much higher than that of N-UA-CNS. After carbon clothes were modified by the obtained materials, the internal resistance of both N-CNS-modified carbon cloth (N-CNS-CC) and N-UA-CNS-modified carbon cloth (N-UA-CNS-CC) was greatly reduced and was found to be only 2.7 Ω and 4.0 Ω, respectively which are all significantly smaller than that of blank carbon cloth (65.1 Ω). These electrodes were assembled in microbial fuel cells (MFCs) as anode, and the operation experiments showed that the N-CNS modification shortened start-up time, improved output stability and increased maximum output voltage significantly. The maximum power density of N-CNS-CC MFC was 1122.41 mW m⁻² which was 1.3 times of that of N-UA-CNS-CC MFC and 1.6 times of that of CC MFC. The results demonstrated that N-CNS was an ideal modification material for fabricating MFC anodes with simple preparation process and low cost. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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Review

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34 pages, 1484 KiB

Open AccessReview

Outlook on the Role of Microbial Fuel Cells in Remediation of Environmental Pollutants with Electricity Generation

by

Asim Ali Yaqoob

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Asma Khatoon

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Siti Hamidah Mohd Setapar

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Khalid Umar

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Tabassum Parveen

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Mohamad Nasir Mohamad Ibrahim

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Akil Ahmad

and

Mohd Rafatullah

Catalysts 2020, 10(8), 819; https://doi.org/10.3390/catal10080819 - 22 Jul 2020

Cited by 93 | Viewed by 6272

Abstract

A wide variety of pollutants are discharged into water bodies like lakes, rivers, canal, etc. due to the growing world population, industrial development, depletion of water resources, improper disposal of agricultural and native wastes. Water pollution is becoming a severe problem for the [...] Read more.

A wide variety of pollutants are discharged into water bodies like lakes, rivers, canal, etc. due to the growing world population, industrial development, depletion of water resources, improper disposal of agricultural and native wastes. Water pollution is becoming a severe problem for the whole world from small villages to big cities. The toxic metals and organic dyes pollutants are considered as significant contaminants that cause severe hazards to human beings and aquatic life. The microbial fuel cell (MFC) is the most promising, eco-friendly, and emerging technique. In this technique, microorganisms play an important role in bioremediation of water pollutants simultaneously generating an electric current. In this review, a new approach based on microbial fuel cells for bioremediation of organic dyes and toxic metals has been summarized. This technique offers an alternative with great potential in the field of wastewater treatment. Finally, their applications are discussed to explore the research gaps for future research direction. From a literature survey of more than 170 recent papers, it is evident that MFCs have demonstrated outstanding removal capabilities for various pollutants. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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22 pages, 2042 KiB

Open AccessFeature PaperReview

Platinum Group Metal-Free Catalysts for Oxygen Reduction Reaction: Applications in Microbial Fuel Cells

by

Maida Aysla Costa de Oliveira

,

Alessandra D’Epifanio

,

Hitoshi Ohnuki

and

Barbara Mecheri

Catalysts 2020, 10(5), 475; https://doi.org/10.3390/catal10050475 - 26 Apr 2020

Cited by 32 | Viewed by 5479

Abstract

Scientific and technological innovation is increasingly playing a role for promoting the transition towards a circular economy and sustainable development. Thanks to its dual function of harvesting energy from waste and cleaning up waste from organic pollutants, microbial fuel cells (MFCs) provide a [...] Read more.

Scientific and technological innovation is increasingly playing a role for promoting the transition towards a circular economy and sustainable development. Thanks to its dual function of harvesting energy from waste and cleaning up waste from organic pollutants, microbial fuel cells (MFCs) provide a revolutionary answer to the global environmental challenges. Yet, one key factor that limits the implementation of larger scale MFCs is the high cost and low durability of current electrode materials, owing to the use of platinum at the cathode side. To address this issue, the scientific community has devoted its research efforts for identifying innovative and low cost materials and components to assemble lab-scale MFC prototypes, fed with wastewaters of different nature. This review work summarizes the state-of the-art of developing platinum group metal-free (PGM-free) catalysts for applications at the cathode side of MFCs. We address how different catalyst families boost oxygen reduction reaction (ORR) in neutral pH, as result of an interplay between surface chemistry and morphology on the efficiency of ORR active sites. We particularly review the properties, performance, and applicability of metal-free carbon-based materials, molecular catalysts based on metal macrocycles supported on carbon nanostructures, M-N-C catalysts activated via pyrolysis, metal oxide-based catalysts, and enzyme catalysts. We finally discuss recent progress on MFC cathode design, providing a guidance for improving cathode activity and stability under MFC operating conditions. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

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