bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selectivity Control in the Electroreduction of CO2 over Nanostructured Catalysts
Authors: Mistry Hemma , Varela Ana Sofia , Reske Rulle , Strasser Peter , Roldan Beatriz 
Published: February 2020

The electrocatalytic reduction of CO2to industrial chemicals and fuels is a promising pathway to sustainable electrical energy storage and to an artificial carbon cycle, but is currently hindered by the low energy efficiency and low activity displayed by traditional electrode materials. In order to overcome these challenges, we have explored how catalyst nanostructure and oxidation state can be used to control the activity and selectivity of the reaction.
Using the inverse micelle synthesis method, nanoparticles (NPs) with well-defined size and interparticle distance supported on glassy carbon electrodes were prepared and tested as catalysts for CO2 electroreduction. Previously, we have reported the dramatic effect of the size of these NPs size on activity and selectivity for Cu1 and Au2 NPs. Here, we will show that interparticle distance is also a critical parameter for controlling reactivity.3 For largely spaced NPs, we find that selectivity to CO is enhanced, since this reaction intermediate is less likely to readsorb on neighboring NPs after formation. Large NPs which are highly spaced have slightly higher hydrocarbon selectivity than smaller NPs, since there is more chance for the intermediates to readsorb on the same particle. On the contrary, for closely spaced NPs we find that hydrocarbon selectivity is enhanced, since the re-adsorption of reaction intermediates on neighboring NPs can facilitate the multi-step pathway required for hydrocarbon production. These results are also corroborated by theoretical diffusion calculations. This study addresses previously unexplored aspects of how product selectivity can be controlled using mesoscale transport processes during CO2 electroreduction. In addition, it shows that IP distance is a critical design parameter to consider when developing improved NP catalysts for CO2electroreduction.
Another critical parameter for selectivity control in nanostructured electrocatalysts is the oxidation state. We will discuss new oxide-derived metal catalysts that can reduce CO2 with lowered overpotential and improved hydrocarbon selectivity. We will also discuss critical insights into the catalyst reaction mechanism which were unraveled using structural and chemical information on the sample during the reaction using operando X-ray absorption fine structure spectroscopy.

References

1) R. Reske, H. Mistry, F. Behafarid, B. Roldan Cuenya, P. Strasser, J. Am. Chem. Soc. (2014) 136: 6978-6986.
2) H. Mistry, R. Reske, Z. Zeng, Z. Zhao, J. Greeley, P. Strasser, B. Roldan Cuenya, J. Am. Chem. Soc. (2014) 136: 16473-16476.
3) H. Mistry, F. Behafarid, R. Reske, A. S. Varela, P. Strasser, B. Roldan Cuenya, ACS Catal. (2015), DOI: 10.1021/acscatal.5b02202.
Enhancement in Production of Electricity from Wastewater Using Microbial Fuel Cell
Authors: Joshi Jarina 
Published: February 2020

A two compartment model of microbial fuel cell was designed. The cells were made from wastewater as electrolyte. Saccharomyces cerevisae was cultured in anodic compartment. The maximum power of 10.745w/m3 was obtained on the 5th day when cellulose acetate was used as the proton exchange membrane (PEM) utilizing waste water as a substrate while supplying external resistance of 500 ohm. There was slight decrease in the power when PEM used was coated cellulose acetate i.e 9.156w/m3 and the power dramatically decreased when nafion membrane was used producing the power of 4.34w/m3. The continuous flow of 1%hydrogen peroxide at the rate of 1 ml/min in anodic compartment in similar conditions increased the power to 22.145w/m3.
Tailoring Microbial Fuel Cells for Production of Hydrogen Peroxide
Authors: Young Michelle , Ki Dongwon , Stadie Mikaela , Thompson Julia , Chowdhury Nadratun , Popat Sudeep , Rittmann Bruce , Torres César I 
Published: February 2020

Microbial fuel cells (MFCs) have been studied for over a decade for possible applications of generating electrical power from wastewater treatment. The power densities achieved so far – although increased by orders of magnitude since the first studies – are still well below those required to compete with other anaerobic treatment processes.
We are exploring the use of MFCs for the production of hydrogen peroxide (H2O2). H2O2 is a powerful oxidant and disinfectant that can be used onsite at a treatment plant. Its production in MFCs is possible by allowing the 2-e- oxygen reduction reaction (ORR) to occur at the cathode. We have studied several aspects of the selection of cathode catalyst, design of the MFCs, and their operation, to optimize the rates and concentrations of H2O2 that can be achieved in a continuous-flow catholyte scheme.
First, we determined the thickness of the Vulcan carbon catalyst necessary for the cathode to promote the 2-e- vs. the 4-e- ORR, as higher thicknesses tend to lead to the consumption of H2O2 within the catalyst layer. Next, we studied various anion exchange membranes (AEMs) for their compatibility with H2O2. Although high-conductivity AEMs are desirable to decrease Ohmic overpotentials, we had to select an AEM that has a relatively low conductivity, because of its higher compatibility with H2O2 that would allow long-term operation. We also optimized the catholyte composition and hydraulic retention time (HRT) within the MFCs to allow for H2O2 production at a high cathodic Coulombic efficiency, by avoiding its disintegration within the cathode chamber.
Through these advances, we have been able to show consistent H2O2 production in MFCs fed with acetate as the electron donor on the anode to concentrations of >0.3%. These concentrations are significantly higher than those needed for many of the possible onsite applications of H2O2, for e.g. disinfection. Our results should pave the way for further development and scale-up of MFCs for the production of H2O2.
On Design, Operation, and Characterization of Microbial Electrochemical Cells with Reduced Overpotentials
Authors: Ki Dongwon , Popat Sudeep , Torres César I 
Published: February 2020

One of the main performance challenges in microbial electrochemical cells (MXCs) is the low voltage efficiency in comparison to other fuel and electrolysis cells. For example, in the case of microbial fuel cells (MFCs), a theoretical maximum of 1.1 V is available when coupling acetate oxidation at the anode to O2 reduction at the cathode, while at current densities of > 5 A m-2, only < 0.3 V is produced, representing > 0.8 V of overpotential. Similarly, although the theoretical applied voltage in microbial electrolysis cells (MECs) is only 0.14 V, the actual applied voltage can be as high as 1.2 V, representing close to 1 V of overpotential. Thus, there is a need to consider design and operation tactics for MXCs that help reduce the overall overpotential in the system. In this study, we aimed to improve the design and operation of MECs to achieve current densities >10 A m-2 with reduced applied voltages, using a thorough analytical framework involving electrochemical techniques such as chronoamperometry, voltammetry and electrochemical impedance spectroscopy. We developed a design that allows high surface area for the anode using carbon fibers, but without creating a large distance between the anode and the cathode (<0.5 cm) to reduce Ohmic overpotential. We determined that Ohmic overpotential, at current densities >10 A m-2 remained <0.1 V even when using an anion exchange membrane to separate the anode and the cathode. We observed the largest overpotential from cathode related phenomena. The increase in pH in the cathode chamber, often to ~13, results in >0.3 V of Nernstian concentration overpotential. We showed how by adding CO2 to the cathode, this overpotential could be reduced to negligible. We revealed that the benefit of CO2 was primarily on the pH and not necessarily on the cathode activation overpotential through electrochemical impedance spectroscopy on the cathode. We also tested two different cathode materials (stainless steel and nickel) to compare the cathode activation overpotentials. Overall, through our design and operation improvements, we were able to reduce the applied voltages from 1.1 to ~0.85 V, at 10 A m-2. However, the cathode overpotential is still a major problem in our reactor design possibly due to local concentration gradients on cathodes, resulting in Nernstian concentration overpotential. To overcome this, it is required to optimize mass transport further between the anode and the cathode, possibly through novel designs and/or improved hydrodynamics at the local surfaces, estimating cathode overpotential ~0.2 V. Then, we estimate that the total applied voltage in MECs at high current densities (e.g. >10 A m-2) could be reduced as low as 0.7 V.
Metallization of DNA Origami to Form Electrically Conductive ~10 Nm Diameter Nanowires
Authors: Uprety Bibek , Harb John N. 
Published: February 2020

DNA based bottom-up nanotechnology is seen as a promising technology for the development of future generations of nanodevices. The bottom-up approach takes advantage of molecular self-assembly to create useful architectures of nanometer dimensions. DNA, with its small size, functional groups and complementary base pairs, is a powerful template for nanodevice fabrication via bottom-up assembly. Recent advances in the field of “DNA origami” have enabled fabrication of nanostructures by folding single-stranded DNA into a variety of 2- and 3-D shapes. However, electrically conductive structures are required for many nanodevice applications.
In this study, we report the fabrication of electrically conductive DNA origami-templated nanowires with the use of gold nanorods (Au NR’s) as a step towards DNA nanodevices. Our process begins with a seeding step where Au NR’s bind to the DNA origami backbone. The seeds are then connected by electroless deposition to make continuous wires. The use of nanorods as seeds provides two key advantages over previous work with particulate seeds. First, the surfactant-enabled anisotropic growth used to initially fabricate the nanorods appears to persist through the electroless plating process on the DNA template. This permits improved control of the width of the final metallized structure since growth in the axial direction is preferred. The average final width of our Au-metallized DNA wires was ~10nm. Continuous 400 nm long DNA wires were obtained by filling gaps between seed particles that ranged from 10.6 nm on average to gaps as wide as 25 nm. The second advantage of nanorods is the reduction in the number of connection points between seed particles by a factor of three relative to that observed for 5 nm seed particles. The reduced number of connection points is expected to increase the conductivity of the wires. Initial electrical characterization of the DNA wires shows that they are conductive, and more detailed measurements are in progress. Site-specific placement of Au NR's on a DNA origami template, demonstrated in this study, is capable of providing the controlled placement needed to enable future nanodevice applications.
In summary, we have demonstrated a metallization process to fabricate thin, high aspect ratio, conductive wires on DNA-origami templates with the use of Au NR’s and electroless plating. Continuing efforts seek to interface these thin nanowires with appropriate semiconducting elements to enable fabrication of self-assembled nanoscale devices.
References:

Uprety, B.; Gates, E. P.; Geng, Y.; Woolley, A. T.; Harb, J. N. Site-Specific Metallization of Multiple Metals on a Single DNA Origami Template. Langmuir
2014, 30, 1134-1141.

Gates, E.P.; Jensen, J.K.; Harb, J.N.; Woolley, A.T. Optimizing Gold Nanoparticle Seeding Density on DNA Origami. RSC Advances
2015, 5, 8134-8141.
The Role of Shewanella Oneidensis MR-1 Structural Proteins in Electrochemical Performance and Biofilm Development
Authors: Cornejo Jose Alberto , Artyushkova Kateryna , Babanova Sofia , Ista Linnea K , Ajo-Franklin Caroline Marie , Atanassov Plamen 
Published: February 2020

Microbial exoelectrogens present promising avenues for the development of bioremediation, biofuel cells and synthetic biology. Our research interests are focused on achieving efficient electron transfer from these organisms embedded in biohybrid constructs while reducing ohmic loses in the system. A crucial aspect for attaining this goal is to fully understand bacterial motility and attachment to the solid support of interest in which respiration occurs. Therefore, biofilm formation is of central interest in anode respiring microorganisms relying on extracellular electron transfer (EET). Microbial appendages have been proposed to be involved in cell attachment as well as in different modes of cell motility prior to the biofilm formation process as observed in select microorganisms [1]. Amongst them, Shewanella oneidensis has been thoroughly used as a model for further understanding microbial electrochemical phenomena. A crucial area of study contributing to the development of microbial electrochemical systems consists in identifying key components involved in the assembly and functionality of pili and flagella in this organism.
Therefore, in this study we utilized motility mutants of S. oneidensis MR-1 that lack key proteins involved in the secretion of type IV pili and flagella. Electrochemical techniques were explored to compare the performance and current generation from microbial fuel cells containing motility-impaired mutants as well as wild type S. oneidensis. Furthermore, we studied and quantified the anodic biofilm morphological characteristics based on microscopic techniques. We found that type IV pili mutants exhibited the highest deficiencies in electrochemical performance and current production based on chronoamperometric studies. Specifically, these deficiencies were more pronounced on PilD and PilT protein-lacking mutants. These complexes are essential inner membrane proteins responsible for pili assembly and contraction [2]. On the other hand, flagella-lacking S. oneidensis mutants did not present significant restrains in current output and biofilm formation.
We conclude that the discussed structural protein assemblies present relevant roles in bacterial surface attachment. Our findings present direct implications in the development of fully engineered biohybrid assemblies, bacteria-anode interactions, and bacterial electron transfer quantification.

Figure 1. SEM images of wild type, pili-lacking and flagella-lacking mutants of S. oneidensisattachedto carbon felt fibers.

References:
1. K.M. Thormann, R.M. Saville, S. Shukla, D.A. Pelletier, A.M. Spormann, Initial phases of biofilm formation in Shewanella oneidensis MR-1. J Bacteriol, 2004. 186: 8096–8104.
2. R.M Saville, N. Dieckmann , A.M. Spormann, Spatiotemporal activity of the mshA gene system in Shewanella oneidensis MR-1 biofilms. FEMS Microbiol Lett. 2010. 308:76–83.

Figure 1
Characterization of Electrochemical Activity in Four Alkaline Hot Springs in Heart Lake Geyser Basin, Yellowstone National Park
Authors: Mohamed Abdelrhman , Medina Adan , Ha Phuc Thi , Peyton Brent , Beyenal Haluk 
Published: February 2020

Yellowstone National Park is well known among microbiologists for its unique microbial ecology, where microorganisms adapt to extreme environments (temperature and pH) associated with geothermal features including hot springs, geysers, and fumaroles. Recently, we developed a portable, battery-operated potentiostat to control the potential of electrodes in in Heart Lake Geyser Basin. The goal of this work is to compare the electrochemical activity in polarized and non-polarized electrodes deployed in alkaline hot springs. We used carbon fabric electrodes (3 inch x 3 inch) working electrode, graphite felt (5 inch x 5 inch x 0.25 inch) counter electrode, and Ag/AgCl reference electrode. A carbon fabric electrode (3 inch x 3 inch) was used as a non-polarized control. These electrodes were immersed in four hot springs with temperature ranging between 45οC and 91οC, and pH between 8 and 8.8. In total, eight polarized electrodes and controls were deployed; one anode and one cathode in each hot spring. The cathodes were deployed approximately 1 foot below the surface of the water, and polarized at -0.6 VAg/AgCl. The anodes were deployed near the bottom of each hot spring at depth 3-10 feet, and polarized at +0.4 VAg/AgCl. All electrodes were deployed for a period of 30 days, and then harvested for electrochemical analysis. Cyclic voltammetry reveals the presence of multiple anodic and cathodic peaks in both polarized and control electrodes. Increased temperature seems to activate redox couples, with anodic (positive current) peaks at -0.2 and 0.35 VAg/AgCl, and two corresponding cathodic (negative current) peaks at -0.4 and 0.25 VAg/AgCl. Temperature-controlled experiments shows that the peak height increases with temperature, which alludes to the presence of thermally-activated electrochemical reactions.
Deep Oxidation of Multiple (Poly)Saccharides at a Bi-Enzymatic Bioelectrode
Authors: Milton Ross D , Yuan Mengwei , Hickey David P , Sugawara Atsuya , Peterbauer Clemens , Haltrich Dietmar , Minteer Shelley D. 
Published: February 2020

As perhaps the most commonly utilized fuel for enzymatic fuel cells (EFCs), glucose oxidation is largely under-exploited. Theoretically, the oxidation of glucose and its downstream metabolites is able to deliver a maximum of 24e- to a bioanode, however the vast majority of EFCs reported to date only perform a single 2e- oxidation of glucose.
Commercially available glucose oxidase (GOx) from Aspergillus sp. oxidizes the anomeric (C1) carbon of glucose. Recently, mediated bioelectrocatalysis of pyranose dehydrogenase from Agaricus meleagris (AmPDH) via an osmium redox hydrogel has been demonstrated, whereby AmPDH is reported to be able to oxidize glucose and other saccharides at combinations of their respective C1/C2/C3 positions.1

Another attractive property of an EFC is the ability to utilize a single biocatalyst to oxidize a range of fuels. We recently reported the use of an engineered commercially-available glucose oxidase with broader substrate specificity at an electrode surface that resulted in an EFC configuration that was able to oxidize multiple (poly)saccharides, including lactose from dairy milk and starch.2

This study reports the ability of a ferrocene redox hydrogel to mediate bioelectrocatalytic saccharide oxidation by AmPDH. Further, AmPDH and broad substrate specificity glucose oxidase were combined to yield an EFC that was able to operate on multiple (poly)saccharides while theoretically increasing the extent of oxidation of each substrate, resulting in a more-versatile EFC with greater efficiency.

References

1. M. E. Yakovleva, C. Gonaus, K. Schropp, P. Oconghaile, D. Leech, C. K. Peterbauer and L. Gorton, Phys. Chem. Chem. Phys., 2015, 17, 9074-9081.
2. R. D. Milton, F. Wu, K. Lim, S. Abdellaoui, D. P. Hickey and S. D. Minteer, ACS Catal., 2015, 5, 7218-7225.

Figure 1
Direct Electron Transfer Mechanisms Applied Toward the Development of an Enhanced Photoelectrochemical Biofuel Cell
Authors: Lopez Ryan J. , Shreve Andrew , Atanassov Plamen 
Published: February 2020

Photoelectrochemical biofuel cells (PEBFCs) are hybrid devices which combine the utility of enzymatic redox catalysts with the photon absorbing characteristics of a dye-sensitized solar cell (DSSC). The pairing of these two technologies has been demonstrated to result in a system that improves on the performance of either a traditional enzymatic fuel cell (EFC) or DSSC operating independently1. Furthermore, due to the increased potential provided by a PEBFC relative to an EFC the range of oxidizers used in the cathode can be broadened to produce a variety of useful reduced fuels. Traditionally, PEBFCs have relied on NAD+/NADH intermediates for charge transfer between the anodic redox enzyme and the porphyrin sensitizer. However, recent work by our group has shown that quinoprotein glucose dehydrogenases are capable of efficient, mediator free direct electron transfer (DET) to immobilized heme porphyrins2. DET allows for a further reduction in the electrode overpotential compared to many mediated systems and therefore provides more usable potential for energy conversion.
In the current work a PEBFC utilizing DET mechanisms was developed with the goal of providing efficient electron transfer between the enzymatic catalyst and the porphyrin sensitizer on the anode. The electron transfer was enhanced by photo-excitation of the sensitizer and induced charge separation to a covalently bound n-type semi-conductor (Figure 1). The resulting oxidized sensitizer then readily accepts electrons from the quinoproteins adsorbed to the electrode surface. The open circuit potential (Voc) of the illuminated photo anode was more negative than the same anode in a dark condition by approximately 80 mV (top of Figure 2). The generated current of the illuminated photoanode was also considerably higher at all potentials tested (bottom of Figure 2). To complete the PEBFC, the photoanode is coupled with a cathode utilizing an oxidase enzymatic catalyst and overall performance in terms of surface characteristics, Voc, and total power are characterized. Further applications with regards to possible uses in energy conversion and reforming of simple, abundant substrates such as glucose to more readily useable fuels such as hydrogen will be discussed.
1. M. Hambourger, G. Kodis, M. D. Vaughn, G. F. Moore, D. Gust, A. L. Moore and T. A. Moore, Dalton Transactions, 9979 (2009).
2. R. J. Lopez, S. Babanova, K. Artyushkova and P. Atanassov, Bioelectrochemistry, 105, 78 (2015).

Figure 1
NADH Bioelectrocatalysis at a Naphthoquinone Redox Polymer
Authors: Abdellaoui Sofiene , Milton Ross D , Quah Timothy , Minteer Shelley D. 
Published: February 2020

Nicotinamide adenine dinucleotide-dependent (NAD) enzymes are used by a wide-spread of dehydrogenases which have been used in a large portion of enzymatic fuel cells (EFCs) to date. The oxidation of an EFC’s fuel (such as glucose) results in the generation of enzymatically-generated diffusive reduced cofactor (NADH). Various electrocatalysts and mediators have been employed to electro-oxidize NADH at low potential, such as phenothiazines and rhodium catalysts.1, 2 Naphthoquinones and anthraquinones have also been employed for NADH oxidation in high power EFCs, however their use typically requires an additional enzyme to mediate electron transfer between the quinone and NADH (diaphorase).3

We report the use of a naphthoquinone redox polymer to oxidize NADH, enzymatically generated from glucose oxidation by NAD-dependent glucose dehydrogenase. The naphthoquinone redox polymer serves as a support for enzyme immobilization. Additionally, NADH is oxidized without the requirement of diaphorase.4

References

1. L. Gorton and E. Dominguez, Rev. Mol. Biotechnol., 2002, 82, 371-392.
2. B. Reuillard, A. Le Goff and S. Cosnier, Anal. Chem., 2014, 86, 4409-4415.
3. H. Sakai, T. Nakagawa, Y. Tokita, T. Hatazawa, T. Ikeda, S. Tsujimura and K. Kano, Energy & Environmental Science, 2009, 2, 133-138.
4. S. Abdellaoui, R. D. Milton, T. Quah and S. D. Minteer, Chem. Commun., 2016, DOI: 10.1039/C5CC09161F.

Figure 1