bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Reactivity of Flavonoids with Molecular Oxygen and the Superoxide Anion Radical
Authors: Lewis Tyra , Wallace William , Martic Sanela
Published: July 2021

Phenolic compounds, such as flavonoids have strong antioxidant properties against reactive oxygen species (ROS), such as the superoxide anion radical (O2˙–, SAR). In the biological environment, SAR is naturally generated via a single electron reduction of molecular oxygen.1-3 The production of excess ROS in the body leads to some undesired reactions, resulting in cellular death and subsequently, the onset of some pathological diseases.1 The activity of antioxidants is directly related to their ability to donate an electron to the ROS. Generally, phenolic compounds act as scavengers of ROS in their reactions with the free radicals to prevent possible cell damage and the resulting health complications induced by ROS production.2 Flavonoids also play a role as metal ion chelators, by which their coordination with specific metal ions results in the formation of a metallo-flavonoid complex.4 Biologically relevant metal ions are known to regulate the ROS activity via Fenton reactions, and as, such may also influence the antioxidant activity and capacity of the flavonoid upon complex formation. The role of metal ions and metallo-flavonoid complexes as antioxidants toward SAR is not fully understood. Additionally, reactions with molecular oxygen within the body is also important, thus further evaluation of flavonoids’ and metallo-flavonoids’ reactivity with molecular oxygen is needed. Herein, we evaluated the activity of a flavonoid, Quercetin (QCR) and its complexes with biologically relevant metal ions, Fe(III) and Cu(II) in their reactions with molecular oxygen and SAR. Using cyclic voltammetry (CV), the current and potential associated with an in-situ generated O2˙–/O2 redox couple was used to monitor the quenching abilities of the additives. CV data indicated a decrease in anodic and cathodic peak currents, but differential reactivity and quenching of molecular oxygen and SAR. Data also suggested that the reactions with QCR, metal ions and their metallo-QCR complexes is driven by an electron transfer mechanism.

L. Zabik, S. Anwar, I. Ziu, and S. Martic-Milne, Electrochim. Acta,
296, 174-180 (2019).

Ahmed, F. Shakeel, Czech J. Food Sci., 30, 153-163 (2012).

M. Kasprzak, A. Erxleben, J. Ochocki, RSC Adv., 5, 45853-45877 (2015).
Bioinformatic Insights into Mechanisms of a Halophilic Electroactive Bacterium
Authors: Gaffney Erin M. , Minteer Shelley D.
Published: July 2021

Microbial electrochemistry is a rapidly evolving field for applications in biosensing, electrosynthesis, and renewable energy generation. Microbial electrochemical systems benefit from long-term operation owing to the self-replicative nature of bacteria allowing for infinite renewable catalysts as long as bacterial growth is supported. For maximal use of these systems, extremophilic bacteria that are capable of extracellular electron transfer are often explored to maximize growth and stability in a variety of conditions. Herein, an extremophilic halophilic bacterium, Salinivibrio sp. EAGSL is shown to have anodic respiring activity as well as capability to grow in a large variety of pH, saline concentrations, and heavy metal concentrations. Bioinformatic analysis was employed to investigate the cellular mechanisms at place for this bacterium’s unique characteristics. The insight gained from the bioinformatic analysis allows for development of microbial electrochemical systems in environmentally relevant media paving the way for the future application of these technologies.
Li7La3Zr2O12 solid-State Electrolyte Modified LiNi0.8Mn0.1Co0.1O2 Cathode Materials for 18650 Lithium-Ion Batteries
Authors: Bunyanidhi Panyawee , Duriyasart Farkfun , Chiochan Poramane , Sawangphruk Montree
Published: July 2021

Ni-rich layered oxide materials as LiNi0.8Mn0.1Co0.1O2 (NMC811) are considering to be the candidate for a next-generation battery technology due to its high energy density. Nonetheless, this material has been suffered from poor rate capability and fast capacity decay, leading to the hindrance of commercialization. In this work, Li7La3Zr2O12 (LLZO) solid-state electrolyte was employed as an additive of NMC811 cathode through the mechano-fusion technique. For the sake of high ionic conductivity and remarkable electrochemical and environmental stability of LLZO, the surface side reactions of NMC811 could be mitigated. As a result, NMC-LLZO in a cylindrical cell type (18650) lithium-ion battery provided the initial discharge capacity of 2300 mAh with a notable capacity retention of 91% after 150 cycles at 1C.

Figure 1
Perovskite-Type Electrolyte for Ceramic Lithium Batteries: Enhanced Microstructure and Bulk Ionic Conductivity
Authors: Yan Shuo , Merati Ali , Abu-Lebdeh Yaser , Pankov Vladimir , Yim Chae-Ho , Bauer Mackenzie , Baranova Elena , Weck Arnaud
Published: July 2021

Solid-state lithium batteries (SSLBs) have shown great potential in energy storage applications, having the potential to enhance energy densities, while providing superior safety compared to conventional liquid electrolyte-based lithium batteries. Perovskite-type LLTO electrolytes are a promising candidate for SSLBs, due to their excellent ionic conductivities with values in excess of 10-3 S cm-1 at room temperature. However, their application in SSLBs is hindered by catastrophic dendrite formation and unstable interfaces during cycling with Lithium metal. It is also difficult to formulate electrolytes with desirable mechanical properties and high bulk ionic conductivity.

Herein, in order to understand the microstructure, bulk ionic conductivity and mechanical properties of the most studied LLTO (Li0.3La0.5TiO3), cold-press sintering was used to prepare pellets with different thicknesses using a mixture of coarse and fine LLTO powders: D50=~40μm, and D50=~1μm, respectively. This significantly enhanced the compactness and density achieved in the cold pressing stage. The sintered pellets showed a modified grain boundary pattern with an enhanced bulk ionic conductivity of 10-4-10-6 S cm-1 between 20˚C and 60˚C and a low activation energy of ~0.21eV. Symmetric cells and half-cells using the as-prepared pellets are currently being assembled for further electrochemical characterization.
Phase-Inversion Polymer Composite Separators for Printable Lithium-Ion Batteries
Authors: Katz Michelle Eileen , Cobb Corie Lynn
Published: July 2021

Separators isolate the anode and cathode electrodes in Lithium-ion (Li-ion) batteries and play a critical role in facilitating ion transport while enabling safe battery operation. Commercial polyolefin separators made of polypropylene (PP) and polyethylene (PE) are used widely in traditional liquid electrolyte Li-ion batteries. However, these materials have limited thermal stability and are not compatible with additive manufacturing approaches for fabrication of new battery electrode architectures [1]. Researchers have investigated phase-inversion composite separators as a means to solve these problems, but there is limited data available on the relative effects of material composition and processing conditions on final separator morphology and performance. In our work, we analyze the effects of solvents, inorganic additives and phase inversion processing conditions on the separator’s ionic conductivity, rate capability, and mechanical integrity. Silica (SiO2), alumina (Al2O3), and glass particles are used as inorganic additives in varying combinations and ratios in a polyvinylidene fluoride (PVDF) polymer matrix. The PVDF concentration in our solvent solution is varied to understand the impact of solution viscosity on the phase inversion process and resultant mechanical performance of our separators. Through this study we begin to elucidate relationships between processing conditions, material composition and electrochemical and mechanical performance to facilitate further development of alternative Li-ion battery separators that are compatible with additive manufacturing.

[1] Cobb, C. L.; Ho, C. C. Electrochem. Soc. Interface
2016, 25 (1), 75–78.

Acknowledgement

This work was funded in part by a Defense Advanced Research Projects Agency (DARPA) Young Faculty Award under grant number D19AP00038. The views, opinions, and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.
Spearheading the Electrification of Chemical Manufacturing with Smart Organic Electrosynthesis
Authors: Blanco Daniela Eugenia
Published: July 2021

Chemical innovation and new molecule development are at the heart of pharmaceutical technologies that commit to the delivery of the finest treatments for challenging diseases. Organic electrosynthesis offers multiple advantages within the industry, enabling the synthesis of new molecules and offering opportunities for more sustainable manufacturing processes through reduced waste streams, near-ambient operating conditions, and a reduced number of reaction steps. However, despite these advantages, electrochemical process development in pharma is often hindered by lengthy and complex optimization approaches, which are required to ensure the purity and selectivity necessary for successful manufacturing. In fact, developing and optimizing electrochemical reactions repeatedly requires extensive experimental campaigns to elucidate reactive behavioral trends and the effect of relevant process variables (e.g. reactant concentrations, electrode potential, temperature, pressure, flow rates) on reaction performance.

Machine-learning (ML) predictive algorithms can be used to predict reaction performance, removing the need for exhaustive experimentation in reaction discovery and process development. However, most ML-enabled systems require the use of large datasets (i.e. 100’s-1000’s of points) to deliver accurate predictions, while gathering experimental points is expensive in human and material resources. The challenge of building large datasets can be averted by developing an innovative framework around the use of supervised machine learning (SL) and active learning (AL) tools. SL models can use small datasets to predict system performance for a significantly larger number of experimental conditions. However, prediction accuracy is heavily reliant on the presence of statistically significant points in the training dataset, which can be challenging to pinpoint. To circumvent this issue, we couple SL with AL algorithms, enabling informed and smart decisions on the experimental campaign design, ultimately reducing the number of experiments required to achieve reliable predictions of reaction behavior.

Addressing fundamental questions regarding the limitations of a disruptive AL-enhanced ML predictive approach, we elucidate the pathway for the design and implementation of intelligent experimental campaigns in organic electrosynthesis. The insights from this work innovate on the future of reaction engineering and process optimization, while lowering the barrier to implementation of more sustainable electrochemical processes in pharmaceuticals and other sectors of the chemical industry.

Figure 1
Activating Metalloenzymes By Electricity: Bioelectrocatalytic Aerobic Oxidation in the Synthesis of Islatravir
Authors: Ruccolo Serge , Zhang Shaoguang
Published: July 2021

Electrochemistry is a green and sustainable technique that has been widely applied in bioanalysis, organic synthesis and energy conversion. Despite the huge potential for green and selective synthesis, bioelectrochemistry is uncommon in synthetic organic applications. The recently disclosed fully biocatalytic cascade synthesis of the HIV drug islatravir represents a groundbreaking approach to pharmaceutical manufacturing. The first step in the synthesis is the biocatalytic desymmetrizing oxidation of ethynyl glycerol to (R)-ethynyl glyceraldehyde. This oxidation process requires 3 redox enzymes: Cu-dependent galactose oxidase (GOase) together with two auxiliary enzymes: catalase and horseradish peroxidase (HRP). While elegant, this three-enzyme system introduced a significant cost and protein burden. GOase is critical to achieving enantioselectivity, while HRP is proposed to facilitate generation of catalytically active intermediate through modification of the oxidation state of the GOase active site. Thus we sought electrochemical strategies to achieve enzyme activation and replace HRP. Here we disclose the development of bioelectrocatalytic aerobic oxidation of alcohols under mild conditions, using a water-soluble ferrocene derivative as the electrocatalyst. Mechanistic insights into the electrochemical activation of GOase were gathered by interrogating the enzyme redox properties and the electron transfer rates between GOase and the electrochemically generated oxidants.
(Invited) Toward MOF-Enabled Solar Cells. Light Harvesting, Energy Transport, Exciton Splitting, and Delivery of Electrons to Electrodes or Catalysts
Authors: Hupp Joseph , Goswami Subhadip
Published: July 2021

Prof. Parkinson is a pioneer and innovator in the creation of unique electrochemically enabled solar cells. Over the past few years his interests here have included unusual new organic materials that offer permanent and highly ordered molecular-scale porosity. This presentation will focus on related materials, i.e. metal-organic frameworks (MOFs), and their potential application to solar-energy-relevant photoelectrochemistry. By way of two or three examples, the talk will describe some of what we have learned about MOF-based harvesting of visible light, characterization of photo-generated excitons, anisotropic propagation of captured energy via diffusion of molecular excitons, splitting of transported excitons into holes and electrons, and delivery of electrons to catalysts and/or electrodes.
(Invited) Perovskite Nanocrystals As Photosensitizers
Authors: Kamat Prashant V , Cho Junsang , DuBose Jeffrey
Published: July 2021

Lead-free double perovskites such as Cs2AgBiBr6 are gaining attention because of their environmental friendliness compared to the lead halide perovskites. The Cs2BiAgBr6 QDs exhibit rich excited state dynamics and when adsorbed onto semiconductor oxides they induce ultrafast charge injection process. Whereas the electron transport layer such as TiO2 or ZnO facilitate transport of electrons to the collecting surface, it can also indirectly induce surface oxidation of QDs if holes are allowed to accumulate. Under steady state photolysis (ambient conditions) the electrons injected into TiO2 are scavenged by atmospheric oxygen, leaving behind holes which accumulate within the quantum dots (QDs). These accumulated holes further induce oxidation of QDs, resulting in the overall photodegradation of perovskite film. Annealed films of Cs2AgBiBr6 nanocrystals, when employed as an active layer in solar cell, delivered photocurrent under visible light excitation. Although Cs2BiAgBr6 is attractive as lead free perovskite materials, the photovoltaic performance remains rather poor. New strategies are needed to implement these double perovskites in solar cells in a more effective way
(Invited) Mulling over Nanoemulsions: Interfacial Molecular Structure, Stabilization and Assembly
Authors: Richmond Geraldine
Published: July 2021

Nanoemlusions are finding numerous applications in the fields of pharmaceuticals, food production, materials synthesis and cosmetics. With the search for broader and improved usage of these unique droplets comes the need to better understand the molecular interactions at the surface that lead to their stabilization. This presentation will focus on our most recent efforts to understand the molecular assembly and structuring present at an oil-water droplet surface that contributes to the stabilization of these nano-sized oil droplets in water, and similarly sized water droplets in oil. The studies are a combination of spectroscopic and thermodynamic measurements coupled with theoretical simulations.
(Invited) Linking Microporous Structure and Surface Properties with Energy Storage Device Performance of Well-Aligned Electrospun Carbon Fiber Electrodes
Authors: Li-Oakey Katie , Tan Shuai , Krau Theodore John , Barnes Pete , Xiong Claire
Published: July 2021

In an effort to more extensively utilize abundant US coal reserves, a zero-waste approach to depolymerize raw Powder River Basin (PRB) coal was invented using environmentally friendly ionic liquids. Coal-derived carbon nanofibers (CCNFs) mats were electrospun using extracted coal char as feedstock. It was revealed that the surface of resulting CCNFs mats was enriched with oxygen, while detailed porous structure characterization via Brunauer-Emmett-Teller (BET) and Dubinin-Radushkevish (D-R) methods showed significantly enhanced porosity in the microporous regime (micro- (pores < 2 nm). Consequently, it was observed that electrical conductivity also increased significantly, compared to carbon fibers without PRB coal. To investigate how fiber alignment affects physiochemical properties of CCNF, well-aligned CCNFs was fabricated by optimizing process parameters in electrospinning process. Both conductivity and microporous pore volume further increased in the well-aligned fibers, with respect to fibers randomly aligned. Based on electrochemical impedance spectroscopy (EIS), the well-aligned CCNFs also demonstrated excellent electrochemical properties, resulting from a cumulative result of the shortened ion transfer path, facilitated wettability from high surface oxygen concentration. Specifically, well-aligned CCNFs reached the specific capacitance of 1590 mF cm-2 at a current density of 4 mA cm-2 in 6M KOH solution. Moreover, a symmetrical carbon/carbon prototype supercapacitor cell, consisting of well-aligned CCNFs mats as electrodes, generated the energy density of 15 µWh cm-2 at a power density of 0.3 mW cm-2, corresponding to a current density of 1 mA cm-2, a gravimetric energy density of 30 Wh kg-1 at a power density of 0.6 kW kg-1 and volumetric energy density of 18.2 mWh cm-3 at a scan rate of 50 mV s-1. Finally, 93.0% specific capacitance remained after 10,000 cycles of galvanostatic charge-discharge, demonstrating that the CCNFs mats possess desired durability. Preliminary results showing CCNF performance as electrodes in sodium ion coin batteries will be briefly discussed.
(Invited) Discovering Inexpensive, Effective Catalysts for Solar Energy Conversion: Authentic Research Experiences for Students
Authors: Schuttlefield Christus Jennifer D.
Published: July 2021

Since 2005, the NSF-funded Center for Chemical Innovation (CCI) Solar Fuels focused on one of the “holy-grails” of 21st Century in chemistry – the efficient and economical conversion of solar energy into stored chemical fuel, where researchers investigated the critical science underpinning the solar-driven decomposition of water into hydrogen and oxygen. The CCI’s outreach program was deeply integrated into the research mission of the Center. Specifically, we created real-time, hands-on research experiences aimed at discovering inexpensive, stable mixed-metal oxide materials for solar energy conversion. These experiences allow students explore fundamental aspects of chemistry while participating in a meaningful, nation-wide collaborative project in the scientific community. This was accomplished through three distinct combinatorial chemistry projects starting with the SHArK project in 2008, followed by the SEAL kit in 2011 and the HARPOON project in 2013. Despite the sunsetting of the CCI Solar Fuels occurring in 2019, the outreach projects have continued with students across the country intensifying the search for solar energy conversion catalysts. Assessment has shown that students exposed to our experiments are more aware of the challenges and social interactions inherent in scientific research as well as understanding how scientists work on real problems, conduct research and analyze data, and integrate chemistry theory and practice.
Ruthenium Dyes, Charge Transfer, and the Sun
Authors: Cheshire Thomas P , Boodry Jeb , Kober Erin A , Aramburu-Trošelj Bruno M. , Brennaman M. Kyle , Giokas Paul M. , Zigler David , Moran Andrew M. , Papanikolas John M. , Meyer Gerald , Meyer Thomas , Houle Frances
Published: July 2021

The performance of dye-sensitized solar cells (DSSC) and dye-sensitized photoelectrosynthesis cells (DSPEC)—and their constituent chromophores, catalysts, and substrates—is commonly evaluated by photocurrents, product fluxes, and time-resolved spectroscopies. Kinetic models of solar harvesting systems are often built from the data using phenomenological methods (i.e. sum-of-exponential or global fit analyses). Such models cannot be predictive, and therefore offer limited fundamental insights to the efficiencies of charge injection and photocatalysis. We describe an approach to modeling the molecular photophysics, interfacial electron transfer, and charge separation that yields a comprehensive kinetic framework for these processes. Simulations of femtosecond to steady-state dynamics using this framework provide a detailed picture of dye cycling under both pulsed-monochromatic and continuous broadband illumination at 1 sun intensity. The competition between molecular transitions and charge injection will be discussed, including the potential implications for the design of chromophore-catalyst assemblies.
Ionic Distribution at the Ionic Liquid/Water Interface: An x-Ray Reflectometry Study
Authors: Nishi Naoya , Katakura Seiji , Sakka Tetsuo , Bu Wei , Lin Binhua , Schlossman Mark L
Published: July 2021

Electrochemistry at ITIES, which has been extensively studied for the oil (O)/water(W) interface, has been extended to the liquid/liquid interfaces of ionic liquids (ILs), namely, to the IL/W interface [1] and even to the IL/O interface [2,3]. One of several characteristics of ILs, compared with conventional molecular liquids like W and O, is the formation of ionic multilayers [4-6] at the interfaces due to the excluded volume and local electrostatic interactions between ions. Although such a multilayering behavior of ILs had been expected to appear in the electric double layer (EDL) at the IL/W interface, it had been challenging to detect the ionic distribution at the IL/W interface.

In the present paper, we will introduce our recent study on the ionic distribution at the IL/W interface, revealed by x-ray reflectometry (XR) using the liquid surface reflectometer at NSF’s ChemMatCARS Sector 15-ID at Advanced Photon Source in Chicago [7]. We designed an ionic liquid that has both high hydrophobicity and high electron-density contrast between the cation and anion, which enabled us to widely polarize the IL/W interface and sensitively probe the cation-rich and anion-rich layers by XR, respectively. We observed the growth of alternately charged cation-rich and anion-rich layers along with a polarity reversal of the layers as the potential changed sign. We quantitatively compared the XR results with the BSK model [8], a phenomenological EDL model in ILs that takes into account both excluded volume and overscreening effects, by combining it with the Gouy-Chapman-Stern model for EDL on the W side of the IL/W interface. Our XR data reveal that the excess charge beyond the first ionic layer decays more rapidly than the model prediction, suggesting that the BSK model needs an improvement with which the layering periodicity and decay length are separately evaluated.

References

T. Kakiuchi and N. Nishi, Electrochemistry, 74 (2006) 942.

N.E.R. Cousens and A.R. Kucernak, Electrochem. Commun., 31 (2013) 63.

Y. Kuroyama, N. Nishi, T. Sakka, submitted.

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N. Nishi, T. Uruga, H. Tanida, J. Electroanal. Chem., 759 (2015) 129.

S. Katakura, K. Amano, T. Sakka, W. Bu, B. Lin, M.L. Schlossman, N. Nishi, J. Phys. Chem. B, 124 (2020) 6412.

M.Z. Bazant, B.D. Storey, A.A. Kornyshev, Phys. Rev. Lett., 106 (2011) 046102.
Modulating the Pro-Apoptotic Activity of Cytochrome C at a Biomimetic Electrified Liquid|Liquid Interface
Authors: Gamero Daniel , Bhattacharya Shayon , Cazade Pierre-André , Molina-Osorio Andrés F. , Beecher Cillian , Djeghader Ahmed , Soulimane Tewfik , Dossot Manuel , Thompson Damien , Herzog Gregoire , Scanlon Micheal D.
Published: July 2021

Programmed cell death via apoptosis is a natural defence against excessive cell division, crucial at all stages of life from foetal development to maintenance of homeostasis and elimination of precancerous and senescent cells.

In this presentation, an electrified liquid|liquid bio-interface is demonstrated that replicates the molecular machinery of the inner mitochondrial membrane at the onset of apoptosis. By mimicking in vivo cytochrome c (Cyt c) interactions with cell membranes, our platform allows us to modulate the conformational plasticity of the protein by simply varying the electrochemical environment at an aqueous|organic interface. Our experimental findings supported by molecular modelling show that adsorption, orientation, restructuring, and pro-apoptotic peroxidase activity of Cyt c can all be precisely manipulated. Remarkably, we observe interfacial electron transfer between an organic electron donor decamethylferrocene and O2, electrocatalysed by Cyt c. This interfacial reaction requires partial Cyt c unfolding, mimicking Cyt c
in vivo peroxidase activity.

Our electrified liquid|liquid bio-interface motivates development of biomimetic electrochemical platforms to identify drug molecules that can potentially downregulate Cyt c and protect against uncontrolled neuronal cell death in Alzheimer’s and other neurodegenerative diseases. As proof-of-concept, we demonstrate that bifonazole, predicted to target the heme pocket, inhibits the electrocatalytic activity of Cyt c and switches off O2 reduction.

Figure 1
X-Ray Study of Voltage-Tunable 2D-Lattice to Cluster Transition of Nanoparticles at the Interface between Two Immiscible Electrolyte Solutions
Authors: Amoanu Daniel , Bera Mrinal , Bu Wei , Rotello Vincent , Lee Yi Wei , Erol Cem , Liang Zhu , Schlossman Mark L
Published: July 2021

Previous X-ray scattering measurements demonstrated the formation of a voltage-tunable 2-dimensional lattice of nanoparticles situated at the liquid-liquid interface between two immiscible electrolyte solutions (Nano Letters 2014, 14, 6816−6822). The nanoparticles had Au cores coated with trimethylammonium terminated ligands and the ITIES consisted of NaCl in water and BTPPATPFB in 1,2-dichloroethane. Here, we present additional measurements on this system which illustrate a transition that occurs at more negative potentials. The transition represents a breakup of the 2D monolayer lattice into a disordered sub-monolayer of nanoparticles that coexists with small nanoparticle clusters in the vicinity of the interface. Grazing Incidence Small Angle X-ray Scattering (GISAXS) provides evidence for the breakup of the lattice and the appearance of clusters. X-ray reflectivity (XR) characterizes the relative location along the interfacial normal of the different types of nanoparticle assemblies.
Improving the Durability of Pt-Alloy Nanoparticles for the Oxygen Reduction Reaction in Acidic Media Via Encapsulation
Authors: Sun Qiang , Mukerjee Sanjeev , Jia Qingying
Published: July 2021

The Oxygen Reduction Reaction (ORR) is the desired cathode reaction in Proton Exchange Membrane Fuel Cells (PEMFCs). Carbon-supported platinum alloy (PtM/C) nanoparticles such as PtCo/C are by far the most effective ORR catalysts in PEMFCs. However, the durability of PtM/C is not satisfying, partly owing to the dissolution of the second transition metal M. In this study, by conducting accelerated stress tests (ASTs) on a commercial PtCo/C catalyst in both a rotating disk electrode and a PEMFC, we identified that a significant fraction of the electrochemical surface area (ECSA) loss of the PtCo/C upon the AST was recoverable. This recoverable ECSA loss was tentatively ascribed to the poisoning of the Pt surface by the sulfate ions either from the H2SO4 electrolyte in a RDE or the Nafion in a PEMFC. We further demonstrated that this poisoning effect can be largely suppressed without compromising the activity by encapsulating PtCo/C into thin functionalized carbon overlayers that were tuned to be permeable to H+, O2, and H2O, but not to sulfate ions. The encapsulation may also alleviate the poisoning of ionomer during on the Pt surface during PEMFC operation.

Acknowledgement

This work was supported by Massachusetts Clean Energy Center Catalyst Award Program G00006319 and the US Department of Energy under award number DE-EE0008416 and DE-EE0008075. This research used beamline 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. The authors declare no competing financial interests.

Vielstich, W.; Lamm, A.; Gasteiger, H. A., Handbook of fuel cells: fundamentals technology and applications. Wiley New York: 2003; Vol. 2.

Chung, D. Y.; Jun, S. W.; Yoon, G.; Kwon, S. G.; Shin, D. Y.; Seo, P.; Yoo, J. M.; Shin, H.; Chung, Y. H.; Kim, H.; Mun, B. S.; Lee, K. S.; Lee, N. S.; Yoo, S. J.; Lim, D. H.; Kang, K.; Sung, Y. E.; Hyeon, T., Highly Durable and Active PtFe Nanocatalyst for Electrochemical Oxygen Reduction Reaction. J Am Chem Soc
2015,
137 (49), 15478-85.
Modification and Electrochemical Study of Dimensionally Stable Anodes for the Oxygen Evolution Reaction
Authors: Salverda Allison , Dondapati Jesse S. , Chen Aicheng
Published: July 2021

In order to sustain and support the current level of economic growth, while addressing climate change issues, the development of clean and sustainable resources has become of the utmost importance in recent years. Potential resources such as oxygen and hydrogen can be produced from water electrolysis. There is a great interest in the development of advanced electrocatalysts for efficient water splitting [1,2]. Two-dimensional (2D) nanomaterials like graphene and graphene oxide (GO) can form thin layers on a supporting material for the transformation of properties and, as a result, can be exploited for efficient oxygen evolution reaction (OER) catalysts [3]. Previous research shows that noble metals tend to have a good catalytic activity for the OER; while another metal is added to further improve the electrochemical stability of the catalytic layer. By incorporation of a 2D graphene-based nanomaterial into an established OER electrocatalyst, there is significant potential to improve the OER catalytic activity and stability.

A tantalum iridium oxide (Ta2O5-IrO2) coating is considered to be one of the best electrocatalysts for the OER in acidic media. In the present study, novel Ta2O5-IrO2-rGO coatings with varying loads of reduced graphene oxide (rGO) were designed to investigate the effects of rGO on the catalytic activity and stability of the Ta2O5-IrO2 coating for the OER. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDS) were employed to characterize the morphology and composition of the prepared Ta2O5-IrO2-rGO coatings. Longevity tests revealed that the incorporation of rGO into the oxide layer strongly affected the stability of the Ta2O5-IrO2-rGO electrodes. The electrochemical activities of the prepared Ta2O5-IrO2-rGO electrodes were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The effect of graphene-based nanomaterials on a Ta2O5-IrO2-rGO coating is compared and discussed.

[1] B. Sidhureddy, J. S. Dondapati, and A. Chen, Chem. Commun., 55, 3626 (2019).

[2] J. Cirone, S. R. Ahmed, P. C. Wood, and A. Chen, J. Phys. Chem. C, 123, 9183 (2019).

[3] A. Salverda, J.S. Dondapati, A. R. Thiruppathi, and A. Chen, J. Electrochem. Soc.,
167, 146506 (2020).
Dealloying Ni-Co-Se Electrocatalysts for Efficient and Stable Oxygen Evolution at High Current Densities
Authors: Abed Jehad , Thorpe Steven , Sargent Edward
Published: July 2021

Stable and affordable electrocatalysts are urgently needed to accelerate the transition from conventional fossil fuels to sustainable energy resources such as solar and wind. Over the last two decades, the electrocatalytic splitting of water, and carbon dioxide reduction to hydrocarbons have received great attention, however approximately 90% of the electricity input is consumed at the anodic oxygen evolution reaction (OER) due to poor reaction kinetics. Precious metal-based electrocatalysts (Pt, Ir, Ru) have been commonly used as OER catalysts, but proven uneconomic for large scale industrial deployment. First-row transition metal elements (Ni, Co, Fe) offer a great earth abundant and low-cost alternative for OER.

In this work, we used a two-step novel milling process to produce Ni,Co-based nanocrystalline electrocatalysts. Cryo-milling (mechanical milling of precursors at cryogenic temperatures to achieve alloying) followed by surfactant-assisted ball milling (SABM), to reduce particles to nanoparticle, create stable disordered phases with high surface areas and coordinatively unsaturated active sites for the reaction of OER intermediates.

Two Ni-Co-Se alloys were milled under various conditions and the structural evolution of the systems was monitored using X-ray diffraction (XRD) and electron microscopy. Our results confirmed the production of two fully alloyed ternary systems (NiCo)3Se4 and (NiCo)Se after 6 hours of milling time. The electrocatalytic activity and stability of the catalysts were evaluated by Tafel measurements obtained from linear sweep voltammetry (LSV) and cyclic voltammetry (CV) experiments. We found that Se in NiCo-based alloys stabilized the disordered structure by forming non-transitional clusters and significantly facilitated the production of nanoparticles. In situ X-ray Absorption Spectroscopy (XAS) and electron microscopy revealed that Se was dealloyed during the OER reaction activating the electrocatalysts by facilitating the formation of active Ni-Co oxyhydroxides. On a glassy carbon electrode at 10 mA.cm-2, activated (NiCo)3Se4 demonstrated a stable performance for 500 hours at 268 mV overpotential with a Tafel slope of 42 mV.dec-1. Moreover, the the catalyst was stable for 100 hours while delivering 500 mA.cm-2 at 320 mV of overpotential. This work suggests that milling can potentially be used to produce OER catalysts for industrial application.
Modelling of Patterned Cathode-Membrane Interfaces with Random Roughness for PEMFCs
Authors: Eardley Sam , Andrews James , Du Shangfeng
Published: July 2021

Proton Exchange Membrane fuel cells (PEMFCs) are becoming an increasingly promising piece of power generation technology that can fit into the changing economy as we strive towards a sustainable energy-based future. However, PEMFCs struggle to meet the energy demands of the world, falling short of the capability of other energy sources such as fossil fuels, mainly due to price and energy output compared to the already establish combustion engines. Looking internally into the PEMFC itself, one of the main issues is the limitations of the electrode-membrane interface leading to low ion transfer performance from the catalyst layer to polymer electrolyte membrane. If we can improve the cathode-membrane interface facilitating the oxygen reduction reaction (ORR) rate at the cathode, the rate limiting step, we can increase the overall performance of the fuel cell.

It is believed that by increasing the interfacial area of the cathode-membrane interface, such as applying a prismatic pattern to the morphology, we can increase the active surface area for the membrane electrode assembly (MEA). By varying the prism frequency and relative height, the interfacial area can be tuned to improve the overall power performance of PEMFCs.

In this work, with a LiveLink connection between Matlab and multiphysics software COMSOL, we model the electrode-membrane interface to investigate its influence on the ion-transfer performance of PEMFCs. By varying the number and size of prism peaks applied to the interface, it is shown that we can influence the fuel cell performance whilst maintaining a constant membrane and catalyst loading. The results showed, at an optimal peak frequency and relative height, an improvement of up to 25% was achieved in the power density.

Although research into the prismatic morphology looks promising, there are many other potential options when looking for which morphology could yield the best overall power performance out of a PEMFC. As such, looking not only into prismatic patterning, but also a pyramidal morphology could prove beneficial. We're also looking into how the application of the roughness to the interface, created using a combination of Gaussian and Uniform wave functions, will impact any previous results observed, and allow us to simulate a model that fits better with the real-world findings.

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Electrochemical Sensors and Techniques for Detection of Heavy Metals in Water: African Research Group Contribution
Authors: Okpara Enyioma , Fayemi Omolola Esther , Ebenso Eno
Published: July 2021

Africa as a developing continent is confronted with heavy metals pollution of their various water sources sequel to extending urbanization, growing industrialization and consequent rising anthropogenic activities accompanying development. With poor urban planning, indiscriminate slum settlement budding, unhealthy environmental sanitation, growing industrial and household water effluent, and random disposal of solid waste in the ecosystem, the available water sources decline in quality with the attending development, especially in the Sub-Saharan regions. This environmental pressure leading to the deterioration of water quality among other impacts has in recent time attracted numerous deserving research interests. Several literature reports have considered the quantifications of some of these heavy metals and likely sources in the surrounding ground and surface water. However, the conventional spectroscopic techniques, usually expensive, involving sophisticated instrumentation and requiring high professionalism to operate, have always been employed. Unfortunately, this would never be sufficient in the assessment of heavy metal pollution in our water bodies owing to the extent of the contamination. Hence, this paper reviews the quantification of heavy metal in our ground and surface waters, their sources, adverse health effects and the role of indigenous African electrochemists in the environmental monitoring of these heavy metals using the various voltammetric technique, as a competitive, point of care, low-cost and sensitive alternative to the spectroscopic strategy.

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Synthesis of Polyaniline and Non-Precious Metals on Onion-like Carbon As Catalytic Support for Oxygen Reduction Reaction
Authors: Serrano Rosario Yannelly Ann , González Aponte Kattia M. , Vargas Perez Brenda L , Cunci Lisandro
Published: July 2021

Oxygen reduction reaction (ORR) is of mayor importance for different life processes and energy converting systems such as fuel cells. The development of economical, efficient, and environmentally friendly electrocatalysts for fuel cells is essential in order to put into action clean energy systems. ORR in aqueous solutions occurs mainly through two different pathways, being a four-electron transfer from O2 to H2O the preferred mechanism. To induce this four-electron reduction, an electrocatalyst is used. Pt is the best electrocatalyst to date, but its large-scale applications are limited by its high cost and limited availability. For this reason, non-precious metal catalysts are currently being studied and developed as a replacement for expensive Pt catalysts. Fe and Co in particular, have been reported to enhance ORR activity and four-electron selectivity of the catalysts. In addition, it is also known that catalyst support is one of the critical components in improving the electrocatalytic activity. Onion-like carbon (OLC) are used as support materials for electrocatalysts, as they have been identified as some of the most promising materials due to their high chemical stability, high surface area and high electric conductivity. Although carbon supports have shown an improved ORR electrocatalytic activity, one of the major causes of failure for fuel cell degradation is due to carbon oxidation or corrosion due to the presence of O2 and/or high electrode potential. Combining carbon compounds with conductive polymers, such as polyaniline (PANI), have been shown to combine high ORR activity with unique performance durability. The purpose of this work is to develop and study FeCo-OLC/PANI nanoparticles and their ORR activity when used as electrocatalysts. In this project, nanodiamonds (NDs) are converted to OLC through a pyrolysis process and then oxidized with sulfuric acid and potassium permanganate. After that, they are dialyzed to remove any residue of acid in the particles and, finally, lyophilized. A synthesis is then carried out with the obtained OLC to polymerize them with the aniline monomer. The presence of PANI in the OLC was confirmed by characterizing the particles with Raman, Scanning Electron Microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Energy-dispersive X-ray spectroscopy (EDS). The synthesis is then carried out with the non-precious metals Fe and Co, and the particles characterized with the techniques previously mentioned. For the experiments, a three-electrode cell is prepared, where a glassy carbon (GC) rotating ring-disk electrode (RRDE) will be functioning as the working electrode. A FeCo-OLC/PANI ink is made and then pasted to the surface of the RRDE, where it will be characterized with cyclic voltammetry and ORR experiments carried out. In future works, these nanoparticles will also be characterized using synchrotron techniques.
Synthesis of Polypyrrole on Onion like Carbon As Catalytic Support for ORR
Authors: Gonzalez Sanchez Osvaldo , Vargas Perez Brenda L , Cunci Lisandro
Published: July 2021

One of the world’s main energy source is the fossil fuels, it’s a resource that is not renewable and can cause irreparable damage to the environment. From oil spills into the ocean to carbon emissions of cars are the world’s most significant threat to human health and future and are major contributors to global inequality and environmental injustice. Worldwide efforts are being made to avoid global warming consequences and researchers are willing to work on the replacement of this energy source. The research I am working on it focuses on making a catalyst that is economical, efficient and above all environment friendly. One of the energy conversion system is the oxygen reduction reaction (ORR), which is due to fuel cells. Fuel cells can generate electricity by reducing oxygen electrochemically getting water as a by-product. Using materials with high conductivity can be beneficial in the reaction process. Therefore, we use Onion-like carbon (OLC) as the catalyst support due to their high conductivity and high surface-to-volume ratio. The use of polymers with high conductivity in combination with carbon material have been previously studied for ORR. We use previously polymerized OLC with pyrrole as a support for the catalyst. The OLC/PPy particles produced are dope with nitrogen by the polymerization of the pyrrole monomer. These particles are characterized using the following techniques, Raman, Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). Then synthesis is caried out using nonprecious metals. The non-precious metals that we use are iron and cobalt. The FeCo-OLC/PPy particle is then tested using electrochemical measurements as well ORR experiments. A future work will be characterizing these samples using synchrotron techniques.
(Invited) Hybrid Electrocatalysts for Bioelectrooxidation of Small Alcohols: Ethanol and Ethylene Glycol
Authors: Honorio Franco Jefferson , Rodrigues Antônio Jesimiel G. Rodrigues , Minteer Shelley , Almeida Paula Z , Polizeli Maria Lourdes T. Moraes , De Andrade Adalgisa Rodrigues
Published: July 2021

Over the last decades researchers have focused to enhance the electrocatalytic activity of the biosystems, increasing the energy generation and electronic conductivity into the biofilms. The use of enzymes immobilized onto the surface of electrodes as the main catalyst in biological fuel cells has been extensively reported. A biofuel cell provides a means to obtain clean, renewable energy and have great potential to be used as alternative energy source for low power devices. There still a lot of important issues in the development of these device, one of them, is to obtain the maximum energy from the fuel. In order to enhance the power density of enzymatic biofuel cell (EBFC) it is necessary to increase the degree of oxidation of the fuel, so that all the electrons from the fuel can be harvested. One approach is the immobilization of a group of enzymes to perform a cascade in order to maximize the fuel oxidation. Recently, we have concentrated our goal to the develop hybrid biofilms employing MWCNT in order to immobilize efficiently the enzymes. In this context we added organic catalyst (TEMPO (2,2,6,6- tetramethylpiperidin-1-yl) oxyl) or metallic nanoparticles (MWCNT/Pt, MWCNT/PtSn and MWCNT/Au) to the biofilms to create a hybrid catalytic system able to catalyze the complete electrooxidation of ethanol (ET) and ethylene glycol (EG) into CO2. In the case of ethanol extraction of 12 electrons per molecule at a single hybrid anode has been obtained with success. This simple methodology can replace the use of enzymatic cascade (7-8 enzymes) and may improve the application in biofuel cells. The electrochemical response of the enzyme system (MWCNT-COOH/LPEI/OxOx) at increasing concentrations of ethanol confirms the excellent activity of these hybrid bioanodes. Product analysis by HPLC techniques allowed us to correlate the increase in current with the formation of CO2or other more oxidable compounds as main product. In the case of EG the metallic catalyst was shifting the onset oxidation potential to lower potentials (200 mV) compared with TEMPO. The maximum power densities reached values around 351 µW cm-2 in the case of MWCNT/PtSn-OxOx for EG and 315 µW cm-2 for MWCNT-COOH/Pyrene-TEMPO/OxDc bioanode. Fig 1 show the products formed for EG. The modification of nanomaterials to obtain a large energy output form an enzymatic system will be highlighted. Therefore, the system open a new alternative of high performance hybrid-EBFC-based enabling the development of efficient EBFC based on alcohols.

Acknowledge: FAPESP (grants # 2017/20431-7 and 2014/50945-4 ), CNPq (grant (465571/2014-0) and CAPES 001. Army Research Office MURI (W911NF-14-1-0263).

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(Keynote) Electrolyte and Mass Transport Effects in CO2 Electroreduction
Authors: Koper Marc
Published: July 2021

This talk will discuss how this double layer structure, or more specifically cations in the electrochemical double layer, may affect the kinetics of electrocatalytic H2 evolution and CO2 reduction, both the activity itself ànd the competition. We will discuss both neutral and acidic electrolyte conditions, and will derive new design rules for optimal Faradaic efficiency.