bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrocatalysis By Heme Proteins and Human Liver Microsomes Bound to Magnetic Nanoparticles and Immobilized on Electrodes
Authors: Krishnan Sadagopan , Premaratne Gayan , Nerimetla Rajasekhara , Matlock Ryan , Liu Hongyun , Walgama Charuksha
Published: February 2020

To develop bioelectrodes with high catalytic efficiency in a minimal reactor volume, elegant tailoring of remarkable enzyme catalysts with nanomaterials is promising. In particular, the role of magnetic nanoparticles (MNPs) in enzyme electrocatalysis and electrochemical biosensors has received notable attention recently. Biomolecules bound to magnetic nanomaterials allow easy isolation from the bulk solution involving simple application of a magnetic field. In this study, we designed a biocatalytic system made of peroxidase-like myoglobin, as a model protein, to covalently conjugate with carboxylic acid functionalized MNPs to examine the catalytic stability, scalability, and reusability features of this bioconjugate. Application of the conjugate was effective for electrochemical reduction of organic and inorganic peroxides, and for both peroxide-mediated and electrocatalytic oxidation of the protein substrate 2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) with greater turnover rates and product yields than myoglobin prepared in solution or MNP alone. Enzymes are often difficult to purify and obtaining high yields for practical applications can be very challenging. Moreover, the electrocatalytic stability and achieving direct electron transfer of purified enzyme films on electrodes is another bottleneck. These challenges are even more drastic in the case of enzymes bound to phospholipid membranes. Despite these limitations, we show that drug metabolizing human liver microsomes, a rather complex enzyme matrix, can be successfully attached to MNPs and immobilized on graphite electrodes with enhanced electrocatalytic activity than microsomal film alone in converting drug into its metabolite. In summary, this presentation will focus on cost-effective development and efficient multiple uses of enzyme catalysts and microsomes for biocatalytic, electrocatalytic, and biosensing applications via magnetic nanomaterials conjugation.
Characterization of Mineral Redox Properties By Electrochemical Impedance Spectroscopy
Authors: Bradley Miranda J , Navarro Maya , Tratnyek Paul G
Published: February 2020

A variety of electrochemical methods have been used to characterize the redox properties of minerals, but few have used mineral particles (as found in the natural environment) and even fewer have used electrochemical impedance spectroscopy (EIS). We have developed protocols for forming mineral particles into packed powder electrodes (PDEs), using agarose-stabilized electrolyte in the pore space. Using this approach, PDEs prepared with various iron oxides have been characterized using a range of electrochemical methods: starting with chronopotentiometry to establish a stable open-circuit potential, interspersed with small (+/-10 mV) perturbance linear polarization resistance measurements, EIS, and linear-sweep voltammetry (LSV). The results obtained with magnetite (Fe3O4) are of particular interest because of their relevance (ranging from nanomedicine to biogeochemistry) and implications regarding redox reactions (including passivation) at mineral surfaces. In general, the results obtained are consistent with prior work on Fe3O4 suspensions (e.g., Eocp ≈ 280 mV vs. SHE) or by other methods (e.g., polarization resistance). EIS has been performed on PDEs containing Fe3O4 from a variety of sources and after a variety of pretreatments. Extensive equivalent circuit modeling of the EIS data has been performed to identify the most appropriate models, sensitivity of model parameters, and how operational variables influence the model parameters. An example of the latter is the addition of chemical oxidants (e.g., H2O2) to the electrolyte to provide controlled passivation of the Fe3O3 surface, which causes the expected changes in the EIS model: such as porosity, charge transfer resistance, or double-layer capacitance. Further application of this approach should provide additional insight in the effects of passive film formation on redox active minerals in the environment.
Nitrogen-Doped Hollow Carbon Spheres As a Sensitive Electrochemical Sensor for Simultaneous Determination of Pb (II) and Hg (II)
Authors: Liu Shantang
Published: February 2020

Keywords: Electrochemical sensor; Hollow Carbon Spheres; Anodic stripping voltammetry (ASV); Heavy metal ions.

Heavy metal ions (HMIs) pose a detrimental risk to human health and environment due to their higher toxicity [1]. Among those ions, both mercury and lead are the well-known toxic and relatively widespread water pollutants that could damage to the brain, heart, kidneys, lungs, and the immune system [2]. The electrochemical method as a promising and elegant technique has been widely used for trace detecting of HMIs due to the excellent sensitivity, low cost, short analysis time, and easy portability [3-4].

We fabricated a nanostructured nitrogen-doped hollow carbon spheres (N-HCSs), which was a kind of modified carbon nanomaterials and used in HMIs detection with enhanced performance for the first time. As-prepared N-HCSs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption and desorption analysis, X-ray photoelectron spectroscopy (XPS). Electrochemical properties of modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The operational parameters which have influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH value, and deposition time were carefully studied. Under optimized conditions, the anodic stripping voltammetric performance toward HMIs were evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The detailed study of the enhancing electrochemical response in stripping voltammetry for the individual and simultaneous detection of ultratrace Pb2+ and Hg2+ in drinking water was described. The detection limits achieved (15 nM and 2.35 nM for Pb2+ and Hg2+) are much lower than the guideline values in drinking water given by the World Health Organization (WHO)[5]. In addition, an interesting phenomenon of mutual interference between Pb2+ and Hg2+was observed. When the concentration of Pb is fixed, the sensitivity to Hg lowers a little and the response current of Pd doesn't change with the increasing concentration of Hg. Meanwhile, when the concentration of Hg is fixed, the sensitivity to Pb lowers a little and the response current of Hg does increase with the increasing concentration of Pb. This study provides a novel nitrogen-decorated hollow spheres carbon-based material for the construction of sensitive electrochemical sensors that meet the needs of environmental control.

References

[1] L. Wang, W. H. Xu, R. Yang, T. Zhou, D. Hou, X. Zheng, J. H. Liu, X. J. Huang, Anal. Chem.2013, 85, 3984.

[2] L. Zhou, W. Xiong, S. T. Liu, J. Mater. Sci.2015, 50, 769.

[3] W. Xiong, L. Zhou, S. T. Liu, Chem. Eng. J.2016, 284, 650.

[4] Q. Guan, W. Xiong, L. Zhou, S. T. Liu, Electroanalysis. DOI: 10.1002/elan.201500481.

[5] R. X. Xu, X. Y. Yu, C. Gao, Y. J. Jiang, D. D. Han, J. H. Liu, X. J. Huang, Anal. Chim. Acta. 2013, 790, 31.

Figure 1
(Invited) Electrocatalysis for Hydroxide Exchange Membrane Fuel Cells
Authors: Yan Yushan
Published: February 2020

One of the grand challenges facing humanity today is the development of an alternative energy system that is safe, clean, and sustainable and where combustion of fossil fuels no longer dominates. A distributed renewable electrochemical energy and mobility system (DREEMS) could meet this challenge. At the foundation of this new energy system are a number of electrochemical devices including fuel cells, electrolyzers, and flow batteries. For all these devices electrocatalysis plays a critical role in controlling their performance and cost, and thus their commercial viability. In this presentation, I will focus on our recent work on electrocatalysis for hydroxide exchange membrane fuel cells. In particular I will discuss the hydrogen oxidation mechanisms in base and the development of non-precious metal based hydrogen oxidation catalysts that can replace platinum.
How Intra-Particle Active Site Dispersion Impacts Electrocatalytic Activity
Authors: Kauffman Douglas R. , Alfonso Dominic , Andolina Christopher , Matranga Christopher , Millstone Jill E.
Published: February 2020

D-band position is often used to describe the reactivity of alloy catalysts. However, the spatial separation (dispersion) and geometric arrangement of catalytically active surface atoms can also control the system’s overall reactivity. My talk will discuss how the dispersion of catalytically active Rh atoms within 2-3 nm, ligand-protected Au/Rh alloy nanoparticles directly impacts electrocatalytic H2 oxidation reaction (HOR) activity. The HOR is an interesting model reaction for the Au/Rh system because Rh atoms catalyze H2 oxidation, whereas Au atoms do not. This provides the opportunity to study the composition-dependent evolution of HOR activity as a function of alloy composition (0-100% Rh). We find that HOR activity follows a volcano-type trend. Pure Au particles do not oxidize H2, and peak HOR activity was found for particles containing 21% and 34% Rh. Beyond this optimum Rh content the HOR activity decreased towards that of 100% Rh particles and a commercially available Rh/C catalyst. In fact, HOR activity decreased as a function of (%Rh)-1 beyond peak activity. We rationalize this trend through the dispersion of Rh-containing active sites on the surface of the Au/Rh alloy NPs. Analysis of literature results has identified similar inverse relationships between catalytic activity and composition. First-principles density functional theory (DFT) studies were also used to model H-binding at realistic Au/Rh alloy nanoparticles. H-binding energy is a common metric for predicting HOR activity. We found that Rh incorporation increased the d-band position of Rh containing particles compared with Au. However, did could not identify any relationship between H-biding and d-band energy. These results are in contrast to what would be expected from a purely electronic d-band model, and they provide strong evidence that intra-particle active site dispersion can tune the catalytic activity of alloy nanocatalysts. We hypothesize this phenomenon should also extend to other alloy systems, and active site dispersion provides another tool for controlling the nano-scale chemistry of electrocatalysts.
Toward Proper Understanding of the Nature of the Active Sites in Non-PGM Catalysts and the Redox Mechanism for ORR
Authors: Jia Qingying , Li Jingkun , Mukerjee Sanjeev
Published: February 2020

Developing efficient catalysts based on inexpensive and abundant materials for the sluggish oxygen reduction reaction (ORR) constitutes one of the grand challenges in the fabrication of commercially viable fuel cell devices and metal–air batteries for future energy applications. Despite recent advances in developing active and durable non-platinum group metal catalysts as promising alternatives to Pt, a less empirical synthesis approach is still missing due to the lack of proper understanding of the mechanistic origin of the ORR and the underlying surface properties under working conditions that govern catalytic activity.

Here, by employing in situ x-ray absorption spectroscopy (XAS) together with complementary characterization techniques such as Mössbauer spectroscopy etc., we propose that the distorted Fe2+-N4-Cx moiety, in which the central Fe2+ ion is located out of the N4-plane and at low spin state without the fifth axial ligand, is the active site responsible for the high ORR activity of pyrolyzed Fe-based catalysts. The local structure of this active site under ex situ conditions is drastically different from that obtained under working conditions, and is thus disconnected from the ORR activity. In situ XAS studies further reveal that the ORR is mediated by the reversible Fe2+/3+ redox transitions with potential-dependent population of active sites.1 Accordingly, the high ORR activity of the distorted Fe2+-N4-Cx moiety is attributable to the out-of-plane Fe displacement with low spin state, which leads to high  Fe2+/3+ redox transition potential that minimizes the site-blocking effect at the targeted potential, as well as appropriate number of eg-electrons that favors O2 adsorption.

Figure 1
Molybdenum Sulfide Films By Atomic Layer Deposition As Electrocatalysts in Hydrogen Evolution Reaction
Authors: Shin Hyunjung
Published: February 2020

Control of the amounts of exposed edge sites of molybdenum disulfide (MoS2) is the key to develop the efficient catalyst for hydrogen evolution reaction (HER).  Atomic layer deposition (ALD) method has been well-known for conformal coating of desired materials. However, application of ALD to control the amount of edge site of MoS2 remains exclusive. Here, we demonstrate that ALD was successfully applied to grow MoS2 films together with control the amount of edge sites and high porous morphology. Our data show that the non-ideal mode of ALD growth on planar surfaces could be used in controlling the relative fractions of active-edge sites of MoS2.  In addition, the effect of amount of edge sites to the Tafel slopes and current densities in HER performance was also investigated. We achieved the best catalytic performance of the current densities up to 20 mA cm-2 at -0.3 V versus reversible hydrogen electrode, Tafel slope of 50 to 60 mV/decade, and onset potential of 143 mV vs RHE. Our results are indicative for the first time that ALD approach is a potential strategy in designing HER materials.
Heterojunction Electrode Designed for Saline Wastewater Electrolysis
Authors: Yang Yang , Hoffmann Michael R
Published: February 2020

Electrochemical oxidation is a promising candidate for decentralized wastewater treatment, due to its modular design, convenient operation, and small carbon footprint. In this process, pollutants are oxidized at the anode, while valuable hydrogen is produced at the cathode. Different from water splitting, the ideal anodes in EO process should have high activity toward oxidant generation rather than oxygen evolution. The need to develop highly efficient and durable anode material is a never-ending challenge. Chloride, as a ubiquitous component in wastewater, can be oxidized readily to reactive chlorine species (RCS = OCl­-, HOCl, Cl·, and Cl2·-) to remove pollutants such as organics, ammonium and bacteria. However the speciation of RCS in saline water electrolysis is lacking of quantitative description. The contribution of each RCS species to pollutant removal is still under debate.

The first approach of this study is to develop multi-layer heterojunction anode for RCS generation. IrO2 is an excellent catalyst for water splitting. By depositing a thin film of TiO2 on IrO2 (Ti/Ir), the oxygen evolution reaction is hindered while the selectivity toward chlorine production is greatly enhanced. The further deposition of Sb-SnO2 islands on TiO2layer (Sn/Ti/Ir) provides additional active sites for radical generation. 

As our second approach, a computational kinetic model covering chlorine generation and radical production is established. Combing it with experimental data, chlorine evolution and the furuther oxidation of chlorine to ClO3- and ClO4
- on Ti/Ir anode can be simulated. It is found that Cl·and HO· is produced concomitantly with chlorine on Sn/Ti/Ir anode and Cl2·-is the dominant radical after reaching equilibrium. The rate constant of Cl· production is two to three orders of magnitude lower than that of chlorine generation. The model predicts that the increase of chloride concentration will enhance the chlorine production but quench more radicals, which is in consistance with experimental results.

The best performing Sn/Ti/Ir anode was applied to human wastewater electrolysis. Although Cl2·- is more oxidative than chlorine, chlorine is the major contributor to the removal of organics and ammonium due to its higher concentration.

Figure 1
Interactions of Metal Oxo Species with Platinum-Based Catalysts Toward More Efficient Electrooxidation of Dimethyl Ether: Comparison to Methanol
Authors: Kulesza Pawel J , Rutkowska Iwona Agnieszka , Sek Jakub P. , Zelenay Piotr
Published: February 2020

Methanol is so far the most commonly considered fuel as an alternative to hydrogen. However, the practical performance is limited by several factors, which include the slow kinetics of methanol oxidation and crossover of methanol from the anode to the cathode side of the cell. More recently, there has been growing interest in dimethyl ether (CH3OCH3), a gas commonly used in aerosol propellants, solvents and coolants, as a possible alternative fuel for low temperature fuel cells. Dimethyl ether (DME) is non-toxic, non-teratogenic, non-mutagenic and non-carcinogenic gas. When oxidized to CO2, a CH3OCH3 molecule releases 12 electrons. The fuel has several advantages over typical organic fuels. Unlike ethanol (CH3CH2OH), the CH3OCH3 ether does not require breaking of the C-C bond. A fairly low CH3OCH3 dipole moment results in the lower ether crossover (through the membrane) in comparison to methanol. Dimethyl ether is much less toxic than methanol and can be readily stored and transported using existing technologies. In addition, the CH3OCH3 ether has potentially higher energy density relative to methanol (namely, 8.2 vs. 6.1 kWh kg-1).

Platinum is one of the typical catalysts for the oxidation of organic molecules. It is quite active toward the dehydrogenation step, but suffers from the CO oxidation step. The bimetalic catalysts (e.g. PtRu, PtSn) can lower the onset potential of DME oxidation peak from 0.5 V for Pt/C to 0.4 V vs. Normal Hydrogen Electrode (NHE), but the maximum current densities are obtained on Pt/C.

We propose here to study the electrooxidation of DME at Pt and PtRu nanoparticles that have been deposited onto nanostructured zirconium(IV) oxide matrix (thin film on electrode surface). Zirconia is known to act as a catalytic component capable of enhancing the reactivity of the electrocatalytic system by increasing the overall acidity at the reaction interface. When combined (as a support) with Pt or PtRu centers, the existence of large population of hydroxyl groups on ZrO2 surface is believed to facilitate desorption of CO adsorbates from Pt and to induce their oxidation to CO2. In the presence of nanostructured zirconia (existing in the vicinity of the catalytic metal), the transport of protons at the electrocatalytic interface is also favored. Synergistic interactions between ruthenium and zirconia components are also feasible. In the present report, we will not limit our results to DME, but similar effects have been observed during oxidation of methanol. We are also going to consider combination of Pt or PtRu with the other metal (Pd) or metal (W, Mo) oxo nanostructures.    

The support from National Research Center (NCN), Poland under the MAESTRO Project No 2012/04/A/ST4/00287 is highly appreciated.
Rhodium-Containing Multi-Layered Mixed-Metal Oxides As Active Supports for Dispersed PtRu Nanoparticles during Electrooxidation of Ethanol
Authors: Rutkowska Iwona Agnieszka , Wadas Anna , Rogalinska Aleksandra , Kulesza Pawel J
Published: February 2020

Recently, there has been growing interest in development of fuel cells (e.g. utilizing small organic molecules) as alternative technologies to hydrogen based electrochemical energy systems. For example, ethanol (biofuel) can be ideally oxidized to carbon dioxide thus delivering twelve electrons. But realistically the reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.

Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium. Also gold in combination with platinum has been demonstrated to produce novel high performance bimetallic catalysts.

We pursue a concept of utilization of mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of methanol and ethanol. Among important issues is incorporation of Rh nanostructures capable of weakening, or even breaking, the C-C bond in the ethanol molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of  ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species  as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol is partitioned (at Rh) to methanolic residues further oxidized at PtRu cannot be excluded.
The Effect of Ni in the Pt-Ni Electrocatalyst for the Glycerol Electro-Oxidation Reaction
Authors: Velázquez-Hernández Isaac , Gómez Monsiváis Angelica C. , Álvarez-Contreras Lorena , Guerra-Balcázar Minerva , Ledesma-García Janet , Arriaga Luis Gerardo , Arjona Noé
Published: February 2020

Glycerol, a waste product of biodiesel production, currently has a cost associated with its disposal. Complete glycerol oxidation to CO2 in acid medium is difficult to achieve, but an alkaline medium facilitates this process. It is known, that non-noble metals such as Cu, Ni, Fe and others, decrease the CO-poisoning effect. Pt is a promising electrocatalyst for alkaline medium, however, it requires co-catalysts to enhance the oxidation process. In this work, we evaluate the effect of Ni in PtNi catalyst toward glycerol electro-oxidation by two methods: cyclic voltammetry and in-situ micro Raman Spectroscopy. For this reason, metal nanoparticles of Pt and PtNi were synthesized using Vulcan Carbon as support. According with XRD, crystallite sizes of 4.48 and 4.20 nm were obtained for Pt/C and PtNi/C, respectively. TEM micrographs showed semispherical-shaped nanoparticles with sizes closed to their crystallite sizes. For metallic mixture, X-ray fluorescence revealed metallic composition of Ni65Pt35. Moreover, thermogravimetric analysis showed a metal mass content of 3 wt. % for Pt/C and 18 wt.% for PtNi/C. The electrocatalytic activity toward glycerol electro-oxidation was tested as function of its concentration, variation of nature of the supporting electrolyte and the electrolyte concentration. Pt and PtNi/C showed oxidation potentials of 0.174 and 0.10 V vs. NHE at 0.5M glycerol, respectively. Also, the if/ib rate as parameter for CO-tolerance, indicated that PtNi/C exhibited a higher tolerance with a 3.5-fold higher rate; meanwhile, Pt/C showed a 2.1 rate.
Electrochemical Reduction CO2 to Formate on Cuxo Electrode
Authors: Qiao Jinli
Published: February 2020

In recent years, CO2 conversion using electrochemical catalysis approaches has attracted great attention due to its several advantages such as the controllable electrode potentials, reaction temperature and the recycled supporting electrolytes1. But the low performance of the electrocatalysts (i.e., low catalytic activity and insufficient stability) hinders its practical application1.

Cu have been explored to catalyze CO2 electroreduction due to its low cost, abundant reserve and reasonable overall Faradaic efficiency towards fuel production(e.g. CO, CH4, C2H4, formate, alcohols)2. However, the energetic efficiency of Cu is limited by the large overpotential (>0.7 V) required for CO2 reduction to outcompete H2O reduction3. Furthermore, Cu electrode rapidly lose their CO2 reduction activity2. Achieving efficient Cu-catalyzed CO2 reduction requires preparing Cu particles whose surfaces have active sites that are different from those on the surface of a metallic Cu electrode4. Here, we prepared CuxO particles by a simple one-step hydrothermal synthesis, and applied them to the gas diffusion electrode, these electrodes exhibited good electrochemical performance of high catalytic activity and high selectivity.

The CuxO were prepared using a simple hydrothermal method as follows: 0.04 mol Cupric Acetate Monohydrate and 0.02mol hexamethylenetetramine were mixed under stirring to form a homogeneous solution. Then the mixture was transferred into a 100 mL stainless-steel autoclave and heated at 180℃ for 2 h. Then the precipitate was collected by centrifugation, washed with deionized water and absolute ethanol for several times, until the pH was neutral, finally dried at oven at 85℃ for 12h.

The crystal structure of the product was characterized by XRD and SEM. The catalyst electrode was prepared by CuXO powder bonded with Nafion solution and isopropanol, and spread over the gas diffusion layer (GDL). The catalytic activity of CuXO nanocatlyst supported on GDL as the cathode electrode was measured using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in 0.5M KHCO3 aqueous solution saturated with both N2 and CO2, respectively.

Figure 1 shows the CV curves on the CuxO/GDL electrode. It can be seen that the anodic peaks between 0V~ 0.85V and the cathodic peak between -0.6V~ 0.25V. The onset potential in 0.5M KHCO3 solution saturated with CO2 was found to be at 0.20 V, which is 250 mV more positive than that under N2 ( 0 V). At an potential of -1.25V, the current density in CO2-saturated 0.5M KHCO3
reached 17.1 mAcm-2 (Fig. 1). All the above reults indicates that participation of CO2 reduction contributes to the enhancement of cathodic current.

 References

1. J. L. Qiao, Y. Y. Liu, Y. Y, F. Hong, J. J. Zhang. Chem. Soc. Rev., 43, 631 (2014 ).

2. Y. Hori, H. Konishi, T. Futamura, A. Murata, O. Koga, H. Sakurai, K.Oguma. Electrochimica Acta 50 (2005) 5354–5369.

3. Y.Hori, A.Murata, R.Takahashi. J.Chem. Soc., Faraday Trans. 1, 1989, 85, 2309-2326

4. W. Li Christina and W. Kanan Matthew. J. Am. Chem. Soc. 2012, 134, 7231−7234

Figure 1
Analysis of High Temperature Co-Electrolysis Cells Via Electrochemical and Surface Spectroscopy
Authors: Call Ann V , Tumilson Christopher , Cumming Denis J , Taylor S.F. Rebecca , Hardacre Chris , Elder Rachael H
Published: February 2020

CO2 emissions are a significant environmental problem which has garnered global interest from both the scientific and political community. One method to reduce emissions is to capture CO2 and convert it to useful products, such as chemical feed-stocks. A method to achieve this is via co-electrolysis of CO2 and H2O, using a high temperature solid oxide cell, to produce synthesis gas – an important intermediate to the production of synthetic liquid fuels.

The potential to convert CO2 into synthetic fuel forms a major pathway for global CO2 utilization and could address the issues of depleting fossil fuel reserves and global warming, however, the reaction mechanisms occurring during cell operation for a co-electrolysis system are currently not well understood.   This information is necessary to improve performance by engineering materials and operating conditions which are ideal for high gas conversion rates and long term cell performance.  Previous studies have suggested that carbonate species may be an important intermediate to CO2 reduction during electrolysis and shows dependencies with temperature and applied potential.[1] This study investigates the electrochemical impedance of electrolysis cells to determine potential rate limiting mechanisms occurring during cell operation.  Results correlating cell performance to surface species detected in-situ using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) obtained under varying fuel and temperature conditions will be discussed. 

[1] D.J. Cumming, C. Tumilson, R. Taylor, S. Chansai, A.V. Call, J. Jacquemin, C. Hardacre, R.H. Elder, 

Faraday Discuss., 2015, 182, 97-111
(Science for Solving Society’s Problems Challenge Grant Winner) SPEED: Sanitation and Processing for Energy with Electrochemical Devices
Authors: Reguera Gemma
Published: February 2020

In Nature, highly efficient and diverse consortia of microbes process organic matter, such as agricultural and human wastes, while generating energy for growth and recycling carbon and other vital elements. Driving these reactions are organisms with the ability to extract electrons from the chemical substrates and transfer them to redox-active minerals. One group in particular, Geobacter bacteria, can couple their metabolism to the reduction of insoluble minerals such as iron and manganese oxides. This natural process can be mimicked in electrochemical devices, which provide a poised electrode as electron sink to drive the growth and catalysis of the bacteria. The SPEED technology capitalizes on the synergistic interactions between Geobacter bioelectrodes and targeted bioprocessing microbes to simultaneously sanitize and harvest energy from wastes. The partnership between the two microbes in such Nature-inspired reactors promotes the processing of agricultural, industrial, and human wastes while generating added-value products and enabling water reuse. The versatility of the SPEED technologies is illustrated with scaled-up reactor prototypes which simultaneously process human urine while harvesting energy from waste substrates as biofuels and industrial chemical precursors. Furthermore, SPEED processes can be adapted to any reactor vessels and use inexpensive electrode materials to promote the microbial catalysis. They are deployable and scalable and can be customized to adapt to the needs of the target market, from decentralized systems for sanitation and water reuse to industrial reactors for bioenergy applications.
Bioelectrochemical Systems for Electricity and Hydrogen Production in Biorefinery
Authors: Borole Abhijeet P.
Published: February 2020

Production of renewable electricity and hydrogen in biorefinery can add a significant value towards development of a sustainable bioeconomy for the 21st century. Here, we investigate bioelectrochemical systems for conversion of biomass and waste using biological fuel cells and electrolysis cells.

The ability to extract electrons from biomass components efficiently can lead to novel pathways for production of energy, fuels and chemicals. Understanding the electron transfer and charge transfer issues is critical in developing functional bioelectrochemical cells. Current production from two biomass-derived streams was investigated determining Coulombic efficiency, cathode efficiency and electrical efficiency. The effect of substrate concentration and loading on performance was studied to understand kinetic vs. mass transfer issues. In addition to the electrochemical aspects, bioconversion aspects become critically important for valorizing complex streams such as bio-derived liquids. In addition to sugars, transformation of furanic and phenolic compounds derived from lignin and hemicellulose is important, since they are rich source of electrons. Removal of furfural, HMF, phenolic acids and acetic acid was demonstrated and conversion efficiencies were calculated. Improvements in current density and coulombic efficiency of the bioanode were studied by varying multiple operational parameters. The electron transfer process was measured against the proton and charge transfer steps to identify mechanistic factors controlling the conversion of the complex substrates to electricity and hydrogen.
Computational Approaches for Rational Design of Electrodes for Biofuel Cells and Biosensors Applications
Authors: Matanovic Ivana , Babanova Sofia , Atanassov Plamen
Published: February 2020

Redox enzymes have been extensively exploited as electrocatalysts in biofuel cells and biosensors due to the advantages they have over commonly used inorganic catalysts. For example, they often have higher activity and selectivity than the inorganic catalysts and can operate at biologically benign conditions. However, additional improvements have to be made for the development of enzymatic electrodes with high activity, stability, and ease of production that can lead to broader applications of enzyme-based systems. Immobilization and optimal interaction of the proteins with the support material is one of the key components in the design of enzymatic electrodes. Therefore, rational design of the electrode surface provides one of the most promising routes for creating biofuel cells and biosensors with enhanced performances. Such a design, however, demands deeper understanding of the bio-nano interface interactions as well as efficient enzyme orientation, which can be achieved by the use of various computational approaches. 

Density Functional Theory (DFT) and docking simulations were used to gain a fundamental understanding of the role of different molecules explored as orienting and/or mediating agents in the design and operation of several enzymatic electrodes. Different computational approaches were first used to explain the role of 1,2-benzoquinone, 1,4-benzoquinone, and ubiquinone on the operation and mechanism of electron transfer in PQQ-dependent soluble glucose dehydrogenase anodes (1, 2).  The same approach was also used to understand the role of bilirubin in the bilirubin-modified oxygen reducing bio-cathodes based on bilirubin oxidase. We further studied the interaction of unsubstituted phenothiazine with glucose, lactate and cholesterol oxidases. Namely, it has been shown that the hydrophobic phenothiazine can be utilized for efficient electron transfer in various oxidases. In addition, docking simulations were used to discuss the nature of the interactions between flavins and outer membrane cytochromes of Shewanella spp., which has practical implication in the development of microbial fuel cells.

1.         Babanova S, Matanovic I, Atanassov P. Quinone-modified surfaces for enhanced enzyme-electrode interactions in PQQ-dependent glucose dehydrogenase anodes. Chem Electro Chem. 2014;1(11):2017–28.

2.         Babanova S, Matanovic I, Chavez MS, Atanassov P. The role of quinones in electron transfer of PQQ-glucose de-hydrogenase anodes – mediation or orientation effect. J. Am. Chem. Soc. 2015;137(24):7754-7762.

Figure 1
Influence of Different Morphology of Three-Dimensional Cuxo with Mixed Facets Modified Air-Cathodes on Microbial Fuel Cell
Authors: Li Kexun , Liu Ziqi
Published: February 2020

Three kinds of three-dimensional (3D) CuxO catalysts were prepared to modify activated carbon air-cathode using a facile electrochemical method with addition of surfactants. The maximum power density of MFC using SC-Cu air cathode (added sodium citrate into the electrolyte solution in eletrodeposition process) was 1550±47 mW m-2, almost 77% higher than AC cathode. Specifically, the charge transfer resistance significantly decreased by 89% from 9.3980 Ω to 1.0640 Ω compared to the control. Lumphy and mutually embedded filmy sheet structure were observed in SEM, which provided sufficient active sites for oxygen adsorption and diffusion. In XRD and TEM result, CuxO with mixed facets showed special structure which had a better performance. Crystallization condition of electrodeposited materials played a significant role in their nature electrochemical properties, morphology controlled by surfactant of CuxO exhibited high properties on the air-cathode MFC.
Self-Powered Arsenic Biosensor Based on the Inhibition of Laccase By As3+ and As5+
Authors: Wang Tao , Milton Ross D , Abdellaoui Sofiene , Hickey David P , Minteer Shelley D.
Published: February 2020

Laccase is a multi-copper center enzyme that is able to oxidize phenolic substrates and undergo a four electron reduction of O2 to H2O. The interaction of laccase with different environmental toxins has been reported, whereby laccase can either oxidize pollutants (polyphenols, polyamines and paradiphenols) as fuels or be inhibited by the toxin (mercury and azide).[1] Laccase is also commonly employed within enzymatic fuel cells (EFCs) yielding a biocathode that bioelectrocatalytically reduces O2 to H2O.

Self-powered biosensors are advantageous in terms of portability because they are not reliant on external power sources. In the past, glucose/O2 EFCs have been widely used as self-powered biosensors utilizing laccase as the cathodic biocatalyst.[2] Self-powered biosensors that sense based on enzymatic inhibition by an analyte are an important category of self-powered biosensors and have been extensively studied.[3]

This study reports the first experimental evidence on the inhibition of laccase by two arsenic species (arsenite and arsenate). The mechanism for both inhibitors was determined to follow an uncompetitive inhibition model via UV-Vis assays using 2,2'azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as the oxidant/indicator. Enzymatic inhibition was also studied electrochemically via amperometric i-t experiments. Furthermore, laccase cathodes were employed as part of a conceptual self-powered arsenite/arsenate biosensor, demonstrating sensitivities of 0.91 ± 0.07 mV/mM for arsenite and 0.98 ± 0.02 mV/mM for arsenate. 

[1]              S. R. Couto, J. L. T. Herrera, Biotechnology advances
2006, 24, 500-513.

[2]              E. Katz, A. F. Bückmann, I. Willner, Journal of the American Chemical Society
2001, 123, 10752-10753.

[3]              D. Wen, L. Deng, S. Guo, S. Dong, Analytical chemistry
2011, 83, 3968-3972.

Figure 1
Sediment Surface Anodes As a Microbial Fuel Cell Deployment Scheme
Authors: Richter Kenneth Erich , Chadwick Bart David , Kagan Jefferey Scott
Published: February 2020

Deployment of microbial fuel cells in the marine environment where the anode is buried in the sediment has always been difficult, particularly when anode(s) have been large to maximize power output. Successful burial has required large masses, substantial horsepower resulting in  occassional fuel cell damage (Chadwick et al, 2011) and diver support during deployment, confirmation and follow-on maintenance in order to ensure the anodes are sufficiently buried. Successful deployment is never guaranteed and tends to be limited to softer sediments without surface or subsurface obstructions. These issues become more daunting when deployment in deeper water is attempted. Reimers and others appreciated these obstacles early in their field programs and have deployed fuel cell anodes in chambers, open at the bottom, which when lowered to the sediment become sealed and anoxic (Nielsen, et al 2007). Microbial metabolism at the anodes depends on organic compounds diffusing up from the enclosed sediments or even enhanced by nutritional additives.

We present the design and preliminary data from an alternate approach to these deployment obstacles with a focus on scaling. Carbon cloth, functioning as an anode, is attached to one side of a rolled rubber sheet, Carbon cloth, buoyed by small floats also functions as a cathode and is attached to the other (top) side of the sheet. As with other designs, power output depends on diffusion of organic material to the anode surface. The rubber sheet, deployed as a roll on the sediment, is unrolled on the bottom via hydraulic pressure in flexible hose attached along the length of the rolled sheet (think New Year’s Eve party makers). The roll-out is initiated with a battery-powered well pump. The rubber sheet ensures anoxic conditions around the anode(s) on the bottom side of the sheet. Anode/cathode pairs are connected by potentiastats and individual currents recorded. 

D.B. Chadwick, J.A. Kagan, A.Q. Wotawa-Bergen and W.C. Davis, "Sled for Benthic Microbial Fuel Cell Deployment with Carbon Fabric Anodes," Oceans 2011, IEEE, (2011).

Nielsen ME1, Reimers CE, and Stecher HA 3rd. 2007. Enhanced power from chambered benthic microbial fuel cells. Environ Sci Technol. 41(22):7895-900.
Fabrication and Evaluation of an Air-Breathing Microfluidic Fuel Cell Employed Enzymatic Electrodes for Lactate Oxidation
Authors: Dector Diana , Hickey David P , Milton Ross , Dector Andres , Arriaga Luis Gerardo , Ledesma-García Janet , Minteer Shelley D.
Published: February 2020

Lactate is an important biomarker due to its excessive production by the body during anerobic metabolism. Existing methods for electrochemical lactate detection require the use of an external power source. This work present a light air-breathing bio-microfluidic fuel cell (BµFC) operated with 20 mM lactate in phosphate buffer pH 6.5 as fuel and the integration of an air-exposed electrode as cathode enabling oxygen delivery directly from air. FcMe2-LPEI/LOx (dimethylferrocene-modified linear poly(ethylenimine) hidrogel to simultaneously immobilize and mediate electron transfer from lactate oxidase) and An-CNT/BOD (anthracene-modified multi-walled carbon nanotubes, Bilirubine oxidase, 50mM phosphate buffer at pH 6.5, and TBAB-modified Nafion) were employed as electrocatalyst for anode and cathode respectively.

An open circuit potential and maximum power density of 0.855V and 0.125mW cm-2 (at 0.3V) were obtained respectively, meanwhile the maximum current density was 1.01 mA cm_2. Although this air-breathing BµFC requires technological improvements before being tested in a biomedical device, show potential possibilities, it represents the best performance to date for a microfluidic fuel cell using lactate as fuel.
(Invited) Electrodeposition of Yttrium Alloy from Ionic Liquids for High Performance Oxygen Reduction Reaction Catalysts
Authors: Meng Hui , Adzic Radoslav R
Published: February 2020

The oxygen reduction reaction (ORR) can be greatly improved when the traditional used Pt catalyst is alloyed with yttrium. According to density functional theory calculations, the activity of polycrystalline Pt3Y electrodecan be enhanced relative to pure Pt by afactor of 6-10.[1] Experimental preparation of PtY alloy is limited to physical method such as gas aggregation[2] ormagnetron co-sputtering. [3] The mass activity of ORR at 0.9VRHE is as high as 3.05A mgPt
-1obtained from a PtxY particle of 9nm in diameter.[2]However there is no firm evidence of the possibility of mass production of PtY alloy with high catalytic performance in ORR from chemical method because yttrium reacts with even trace amount of water and oxygen.

To solve this problem, electrodeposition is considered to be a possibility. It is well known that yttrium is extremely basic metal with a reduction potential -2.43VRHE and electroplating of yttrium from aqueous solutions is believedto be unattainable due to intensive hydrogen evolution at such large over potentials. This problem can be solved using ionic liquids as solvent and electrolyte. They are appropriate medium for the electrodeposition of yttrium and its alloys, because the area of electrochemical stability of ionic liquids overlaps the range of reduction potentials of yttrium.[4]

We selected 1-ethyl-3-methylimidazolium tetrafluoroborate to electrodeposit yttrium on glassy carbon substrate.[5]A controlled method is applied to form PtY alloy based on the electrodeposited yttrium. The ORR activity is evaluated by both half cell and full cell characterizations.

References:

[1] J. Greeley, I. E. L. Stephens, A. S. Bondarenko, T. P. Johansson, H. A. Hansen, T. F. Jaramillo, J. Rossmeisl, I. Chorkendorff, J. K. Nørskov, Alloys of platinum and early transition metals as oxygen reduction electrocatalysts, Nature Chemistry, 2009, 1, 552-556.

[2]P. H. Fernandez,F.Masini,D. N. McCarthy,C. E. Strebel,D.Friebel,D.Deiana,P.Malacrida,A.Nierhoff,A.Bodin,A. M. Wise,J. H. Nielsen,T. W. Hansen,A.Nilsson,I. E. L. Stephens, I.Chorkendorff, Mass-selected nanoparticles of PtxY as model catalysts for oxygenelectroreduction, Nature Chemistry, 2014, 6, 732-738

[3]S. J.Yoo , K. S. Lee , S. J. Hwang, Y. H. Cho, S. K. Kim,J. W. Yun, Y. E. Sung, T. H. Lim, Pt3Y electrocatalyst for oxygen reduction reaction in protonexchange membrane fuel cells, International Journal of Hydrogen Energy,2012, 37, 9758-9765.

[4]L. M. Glukhov, A. A. Greish, and L. M. Kustov, Electrodeposition of Rare Earth Metals Y, Gd, Yb in Ionic Liquids, Russian Journal of Physical Chemistry A, 2010, 84, 104-108.
Quantitative Comparison of Atomistic Molecular Dynamics Simulations and X-Ray Scattering of Polymerized Ionic Liquids
Authors: Liu Hongjun , Paddison Stephen J.
Published: February 2020

Polymerized ionic liquids (polyILs) are touted as the ideal solid-state electrolyte materials for electrochemical devices due to enhanced mechanical characteristics of polymer nature and unique physico-chemical properties inherent from ionic liquids. PolyILs offer great flexibility in designing the task specific media through judicious choosing component cations, anions and polymer structures for a wide range of energy conversion and storage applications, such as dye-sensitized solar cells, lithium ion rechargeable batteries, and alkaline fuel cells. While polyILs enjoy many favorable properties such as low flammability, high thermal/chemical/electrochemical stability, and mechanical strength, they inevitably suffer from the retarded ionic conductivity, one of the detrimental shortcomings in electrochemical applications.  PolyILs usually have elevated glass transition temperature Tg and subsequently several orders of magnitude decrease in ionic conductivity with respect to their molecular IL counterparts. Most of previous research involve in finding the optimal polyILs to achieve the maximum accessible ionic conductivity. It is generally accepted that ionic conductivity of polyILs depends on the complex correlations between chemical nature of polymer backbone and counter-ions, glass transition temperature, mesophase morphology, temperature and pressure. Therefore, a molecular-level understanding of the relationship between chemical structure, morphology and ion transport will promote the rational design of polyILs for electrochemical applications.

In present work, we use atomistic molecular dynamics simulations to investigate structural properties of model system poly(1-n-alkyl-3vinylimidzolium bistrifluoromethylsulfonylimide) poly(nVim Tf2N) . X-ray scattering measurement on structural properties of polyILs is elusive. The detailed simulations provide a direct quantitative picture for understanding the structure/morphology of polyILs on the atomic scale. In particular, we present the first direct comparison of structure factors obtained from X-ray scattering and simulations for various alkyl chain length of poly(nVim Tf2N). Excellent agreement is found between the experimental and simulated scattering profiles in terms of peak position and shape, which provides proper validation of our simulation methods.  All characteristic distances (backbone-to-backbone, anion-to-anion and pendant-to-pendant) are well reproduced. As the alkyl chain length increases, the backbone-to-backbone peak becomes stronger, moving to larger distance, the anion-to-anion separation slightly increases with vanishing intensity, and the pendant-to-pendant peak hardly changes. This quantitative comparison of X-ray scattering and atomistic simulations is expected to lead to a molecular-level predictive understanding in structure and morphology of polyILs and paves a substantive step towards the rational design of future polyILs for electrochemical devices.