The nanostructure of three-dimensional scaffolds enhances the current density of microbial bioelectrochemical systems

Flexer, Victoria; Chen, Jun; Donose, Bogdan C.; Sherrell, Peter C.; Wallace, Gordon G.; Keller, Jürg

doi:10.1039/c3ee00052d

Cited by 135 publications

(122 citation statements)

References 35 publications

(74 reference statements)

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“…[29,115]. As shown in Figure 20, the nanoweb can cover the RVC structure uniformly, providing additional surface area for chemical or biological functionalization.…”

Section: Modified Rvc Electrodesmentioning

confidence: 97%

“…As pointed out by the authors, RVC electrodes have found application in microbial fuel cells due to their biocompatibility, high surface area, low cost and high conductivity. Furthermore, recent advances have incorporated advanced materials such as carbon nanotubes to form hierarchical "nanowebs" within the RVC structure [29,115]. Uniform biofilms could develop on this substrate, resulting in an increased activity towards acetate degradation in comparison to bare RVC, reaching current densities up to 6.8 mA cm −2 even in the absence of electrolyte flow.…”

Section: Fuel Cellsmentioning

confidence: 99%

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The continued development of reticulated vitreous carbon as a versatile electrode material: Structure, properties and applications

Walsh

Arenas

León

et al. 2016

Electrochimica Acta

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The limitations of 2-dimensional electrodes can be overcome by using threedimensional materials having sufficient porosity and active area while offering moderate mass transport rates and a relatively low pressure drop at controlled electrolyte flow rate. In concept, a wide variety of metal, ceramic and composite materials are possible but restrictions are imposed by the need to avoid materials degradation, while maintaining adequate electrical conductivity, sufficient robustness and the possibility of facile scale-up. Despite its fragility, one of the traditional electrode materials used as a porous, 3-dimensional electrode is carbon foam, particularly in the 97% vol. porous form of reticulated vitreous carbon, RVC. A timeline indicates that the history of this material dates back over 50 years to the mid1960s, when it was primarily used as an uncoated material in small-scale, laboratory electroanalysis. Surface modification and diverse coatings have considerably extended the use of RVC. Recent applications are found in sensors and monitors, electrosynthesis, environmental processing and energy conversion. This review highlights the fundamental structure and summarises the physicochemical properties of RVC. Fluid flow through various porosity grades of the material, their active electrochemical area and rates of mass transport are quantified. The diverse applications of RVC in energy conversion, environmental treatment and electrosynthesis are illustrated by selected examples from the authors' laboratories and others over the last 30 years. Recent research on coated RVC, energy conversion environmental remediation and sensors is highlighted. Critical areas deserving further research and development are proposed.

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“…[29,115]. As shown in Figure 20, the nanoweb can cover the RVC structure uniformly, providing additional surface area for chemical or biological functionalization.…”

Section: Modified Rvc Electrodesmentioning

confidence: 97%

Section: Fuel Cellsmentioning

confidence: 99%

The continued development of reticulated vitreous carbon as a versatile electrode material: Structure, properties and applications

Walsh

Arenas

León

et al. 2016

Electrochimica Acta

View full text Add to dashboard Cite

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“…foam material of honeycomb structure that has also been used in few microbial fuel cell studies [116,[146][147][148]. RVC has a number of advantages for bioelectrochemical systems such as a very high surface area to volume ratio, high electrical conductivity, strong chemical and heat resistance and minimal reactivity over a wide range of conditions [150].…”

Section: Reticulated Vitreous Carbon (Rvc) Is a Rather Cheap And Commmentioning

confidence: 99%

“…Roughened surfaces offer greater surface and provide more favourable sites for colonization. Increasing the available surface area for biofilm growth by using rough or porous materials is a well-proven strategy for MFC performance enhancement [116,117,127,[146][147][148].…”

Section: Bioanode Electrode Materials -A Brief Overviewmentioning

confidence: 99%

Microbial electrosynthesis from carbon dioxide: performance enhancement and elucidation of mechanisms

Jourdin¹

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Microbial electrosynthesis (MES) of organics from carbon dioxide has been recently put forward as an attractive technology for the renewable production of valuable multi-carbon reduced end-products and as a promising CO 2 transformation strategy. MES is a biocathode-driven process that relies on the conversion of electrical energy into high energy-density chemicals. However, MES remains a nascent concept and there is still limited knowledge on many aspects.It is still unclear whether autotrophic microbial biocathode biofilms are able to selfregenerate under purely cathodic conditions without any external electron or organic carbon sources. Here we report on the successful development and long-term operation of an autotrophic biocathode whereby an electroactive biofilm was able to grow and sustain itself with CO 2 and the cathode as sole carbon and electron source, respectively, with H 2 as sole product. From a small inoculum of 15 mg COD (in 250 mL), the bioelectrochemical system operating at -0.5 V vs. SHE enabled an estimated biofilm growth of 300 mg as COD over a period of 276 days.A critical aspect is that reported performances of bioelectrosynthesis of organics are still insufficient for scaling MES to practical applications. Selective microbial consortia and biocathode material development are of paramount importance towards performance enhancement. A novel biocompatible, highly conductive three-dimensional cathode was manufactured by direct growth of flexible multiwalled carbon nanotubes on reticulated vitreous carbon (NanoWeb-RVC) by chemical vapour deposition (CVD). The results demonstrated that: (i) the high surface area to volume ratio of the macroporous RVC maximizes the available biofilm area while ensuring effective mass transfer to and from the biofilm, and (ii) the nanostructure enhances the bacteria-electrode interaction, biofilm development, microbial extracellular electron transfer, and acetate bioproduction rate.However, for scale-up beyond certain sizes, there are some limitations with the CVD technique. We harnessed the throwing power of electrophoretic deposition technique (EPD), suitable for industrial scale production, to form multi-walled CNT coatings onto RVC to generate a new hierarchical porous structure, hereafter called EPD-3D. A very effective mixed microbial consortium was successfully enriched and transferred to EPD-3D reactors and demonstrated drastic performance enhancement reaching biocathode current density of -102 ± 1 A m -2 and acetate production rate of 685 ± 30 g m -2 day -1 .ii An in-depth understanding on how electrons flow from the cathode to the terminal electron acceptor is still missing but crucial (e.g. for improved reactor design). High rates of acetate production by microbial electrosynthesis was shown to occur via biologically-induced hydrogen, likely through the biological synthesis of metal copper particles, with 99 ± 1% electron recovery into acetate. The acetate-producing bacteria showed the remarkable ability to consume a high H 2 flux (ca. 1.15 m ...

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“…Materials science recently shows promising progress in providing cheaper electrode materials that feature improved surface properties to increase electron transfer rates. [78][79][80] But before general process design steps can be approached a better understanding of the overall net benefits of possible processes of interest is needed.…”

mentioning

confidence: 99%

Understanding extracellular electron transport of industrial microorganisms and optimization for production application

Kracke¹

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Microbial electrosynthesis (MES) and electro-fermentation are novel approaches to increase microbial production by stimulating the metabolism of the cells electrically. The technique is still in its infancy and while already hyped as promising method to convert CO 2 or cheap carbon sources and electrical energy into valuable chemicals and fuels, little is known about its true potential. This project uses a combination of in silico and in vivo approaches to gather novel information about the benefits and limitations of microbial electrosynthesis as well as its fundamental mechanisms.Understanding microbial electron transport mechanisms is the key to optimization of any bioelectrochemical technology. Therefore, this work analyses the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bioproduction.Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bioelectrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g. cytochromes, ferredoxins, quinones, flavins) are identified and analysed regarding their possible role in electrode-microbe-interactions.Based on these findings a stoichiometric network analysis is performed analysing the effect of electrical stimulation on the microbial metabolism theoretically. Escherichia coli is used as model organism for production with the aim to identify target processes for MES.For the first time, 20 different valuable products were screened for their potential to show increased yields during anaerobic electrically enhanced fermentation. Surprisingly it was found that an increase in product formation by electrical enhancement is not necessarily dependent on the degree of reduction of the product but rather the metabolic pathway it is derived from. Contrary to the usual assumption a reduced product would always require electron supply by a cathode this study shows that a complex metabolic analysis is needed to identify the overall redox state of each process. A variety of beneficial processes is presented with product yield increases of maximal +36% in reductive and +84% in oxidative fermentations and final theoretical product yields up to 100%. This includes compounds that are already produced at industrial scale such as succinic acid, ii lysine and diaminopentane as well as potential novel bio-commodities such as isoprene, para-hydroxybenzoic acid and para-aminobenzoic acid. Furthermore, it is shown that the way of electron transport has major impact on achievable biomass and product yields. The coupling of electron transport to energy conservation could be identified as crucial for most processes.The in vivo approach of this project introduces the development of a standardised reactor platfor...

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The nanostructure of three-dimensional scaffolds enhances the current density of microbial bioelectrochemical systems

Cited by 135 publications

References 35 publications

The continued development of reticulated vitreous carbon as a versatile electrode material: Structure, properties and applications

The continued development of reticulated vitreous carbon as a versatile electrode material: Structure, properties and applications

Microbial electrosynthesis from carbon dioxide: performance enhancement and elucidation of mechanisms

Understanding extracellular electron transport of industrial microorganisms and optimization for production application

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