bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of a Solar Device to Transform Wastewater Nitrates to Nitrogen-Species Coupled with Energy and Nutrient Recovery
Authors: Barrera Luisa , Bala Chandran Rohini
Published: February 2020

Excessive anthropogenic production of nitrogen fertilizers combined with rapid industrialization has disrupted the natural balance of the nitrogen cycle leading to increased concentrations of reactive-nitrogen/nutrient species including nitrates (NO3
-), nitrites (NO2
-), and ammonium (NH4
+) in groundwater, rivers and lakes1,2. These nutrient imbalances can lead to health risks to human beings by causing methemoglobinemia in infants, also known as “blue baby syndrome,” and negatively impact the environment by causing acid rain and algal blooms. Despite the chemical energy that is stored in common dissolved contaminants in water, wastewater treatment poses the challenge of being a highly energy intensive process. In this study we propose a photoelectrochemical approach to oxidize water and reduce nitrates (NO3
-) to various nitrogen-species including N2, and other value-added products such as NH3 and N2O. An ion-exchange membrane attenuates gas crossover while facilitating species transport. NH3 can be directly used as a fuel and/or for fertilizer production, and N2O is a powerful oxidant in combustion reactions (used as “nitrox” to supercharge engines of high performance vehicles); in the combustion of methane (CH4), N2O increases the heat released in the reaction by 37% as compared to when O2 is used as an oxidant. Thermodynamic analyses is first performed to predict the solar energy conversion efficiencies for the various product species. Furthermore, a one-dimensional, coupled species transport and reaction kinetics model is developed for a batch reactor to predict overall rates of product formation. Specifically, the model developed is applied to investigate the influences of device-design, competing reactions and mass transport on the rates and the selectivity of product formation. Thermodynamic predictions show that N2O could be a more promising value-added NO3
- reduction product compared to NH3 due to the increased aqueous solubility of the latter, which leads to significant crossover losses.

References:

Falkowski, P. et al. The Global Carbon Cycle : A Test of Our Knowledge of Earth as a System. Science (80).
290, 291–297 (2000).

Duca, M. & Koper, M. T. M. Powering denitrification: the perspectives of electrocatalytic nitrate reduction. Energy Environ. Sci.
5, 9726 (2012).

Figure 1
Photoelectrochemical Hydrogen Generation Using a Bis-Chelating Nickel PNP Catalyst Tethered to Band-Edge Modified Si(111)|TiO2
Authors: Gurrentz Joseph Martin , Boucher Dylan G , Rose Michael J
Published: February 2020

We report the generation of a novel “bis-bidentate” chelating nickel phosphine electrocatalyst functionalized with pendant amines. Two PNP appended donor moieties are tethered to a single surface-tethering anchor, with the intention of leveraging the chelate effect to increase the kinetic stability of the bound nickel ion upon surface immobilization. The carboxylic acid moiety of this bis-bidentate PNP catalyst allows for adsorption to band-edge modified p-silicon(111) photoelectrodes coated with amorphous TiO2 for photogeneration of dihydrogen under illumination and negative applied bias. The synthesis of this ligand also allows for variability in metal oxide binding groups and phosphine R-groups.

The band-edge modification of p-silicon(111) is achieved with a mixed monolayer of phenyl-3,5-bismethoxytriethylene glycol and methyl units, which also enhances electron transport through the interface. An ultrathin film (20Å) of amorphous titania further passivates the semiconductor from the generation of surface defects, acts as an electron selective layer, and allows for adsorption of the metal complex to the electrode.

Cyclic voltammetry and XPS were used in conjunction to estimate catalyst loading, evaluate photoelectrochemical performance of these devices, and investigate different mechanisms of activity loss such as via loss of the nickel or desorption of the ligand. Different modes of device construction, such as via adsorption of the PNP ligand to the TiO2-coated photoelectrodes followed by treatment with a solution of [Ni(MeCN)6]·2ClO4 and via deposition of the fully constructed, metalated complex were evaluated for differences in Ni loading and device performance. Both the adsorbed catalyst as well as non-specifically adsorbed Ni2+ on TiO2 were shown to be active for proton reduction, albeit at different potentials. Efforts were therefore made to isolate the activity of the nickel phosphine catalyst and prevent convolution of the electrochemical response.
Photoreactions with CO/CO2 Promoted By Hot Electrons in Plasmonic Metastructures
Authors: Chang Le , Wang Wenhao , Wang Zhiming , Govorov Alexander
Published: February 2020

Nanostructures and metastructures can be used for generation of energetic (hot) electrons which is a promising mechanism for solar photo-catalysis and photo-detectors. By building metal clusters into metamaterials and using large absorption cross sections of the plasmonic components, one can created hybrid systems where energetic (hot) electrons should make metal clusters more active in catalytic reactions, for example, in the CO2 reduction reaction. However, the central questions in the problem include two parts: how many hot electrons generated in such metamaterials; the other one is how the hot electrons catalyze the chemical reactions. In particular, we show that generation of hot electrons in metamaterials[1-4] leads to various chemical reaction mechanism and reaction pathways, which could be the guideline for producing direct CH4 and other multi-carbon alcohols (C2H3O, C2H4O, C2H5O etc.). Hot-electron generation[2, 4] together with the catalytic reaction mechanism represent efficient methods to transfer and localize optical and photo-chemical energies.

Govorov, A.O., H. Zhang, H.V. Demir, and Y.K. Gun’ko, Nano Today, 2014. 9(1): p. 85-101.

Hartland, G.V., L.V. Besteiro, P. Johns, and A.O. Govorov, ACS Energy Lett., 2017. 2(7): p. 1641-1653.

Sykes, M.E., J.W. Stewart, G.M. Akselrod, X.-T. Kong, Z. Wang, D.J. Gosztola, A.B.F. Martinson, D. Rosenmann, M.H. Mikkelsen, A.O. Govorov, and G.P. Wiederrecht, Nature Commun., 2017. 8(1): p. 986.

Sousa-Castillo, A., M. Comesaña-Hermo, B. Rodríguez-González, M. Pérez-Lorenzo, Z. Wang, X.-T. Kong, A.O. Govorov, and M.A. Correa-Duarte, J. Phys. Chem. C, 2016. 120(21): p. 11690-11699.
Rapid One-Pot Synthesis of Α- and Β-Cu2V2O7 and Their Use in Photoelectrochemical Water Splitting
Authors: Hossain mohammad Kabir , Rajeshwar Krishnan
Published: February 2020

Photoelectrochemical (PEC) water splitting is a promising strategy to make high density chemical fuels via utilization of solar energy using semiconductor materials. Oxide semiconductors, especially transition metal oxide semiconductors, offer various advantages such as stability, Earth-abundance and easy fabrication. A twin-photoelectrode tandem cell approach appears to be the most viable route to high solar-to-hydrogen conversion (STH) efficiency. In this configuration, the optimual energy bandgap for the semiconductor photoanode has been estimated to be ~ 2 eV. Ternary copper vanadates fulfill this criterion. The compound, Cu2V2O7 exists in two stable polymorphs at room temperature: orthorhombic α-Cu2V2O7 (Blossite) and monoclinic β-Cu2V2O7 (Ziesite). There are limited reports on the PEC behavior of β-Cu2V2O7, however, no corresponding reports on α-Cu2V2O7 are available.

In this present work, we report the synthesis of these two polymorphs using a rapid and simple one-pot solution combustion synthesis and document their PEC behavior. The effect of various synthetic parameters were investigated and thus enabled to identify the optimum growth conditions to achieve phase-pure samples. Rietveld refinements along with powder X-ray diffraction confirmed the phase purity of the two polymorphs. The bandgap values of these oxides were estimated employing two different methods: Tauc plot from diffuse reflectance spectroscopy and surface photovoltage spectroscopy. These values agreed with those derived from density functional theory (DFT) calculations. Fermi level energies were quantified from contact potential difference (CPD) measurements which positioned them close to the conduction band minima (CBM) and thereby confirmed their n-type conductivity. The β-Cu2V2O7 phase showed higher photoactivity at lower applied bias; however, both phases showed similar photoactivity toward water splitting at higher applied bias.
Characterization of Water Oxidation Amorphous Thin Film Catalysts By X-Ray in-Situ analysis
Authors: Kwon Gihan , Risch Marcel , Cho Byeong-Gwan , Chang Seohyung , Heo Jineun , Kim Hacksung , Tiede David M , Kim Jungho
Published: February 2020

To understand water oxidation performance such as cobalt oxygen evolution catalysts (OECs: CoPi and CoBi) and Iridium OECs (IrPi, IrOx, IrBL), we currently utilize pair distribution function (PDF)/x-ray absorption spectroscopy (XAS) for structural information and resonant x-ray emission spectroscopy/resonant inelastic x-ray scattering (RIXS)/ to determine the electronic structure of amorphous thin film OECs. These multi-modal analytical approaches clearly show that CoPi and CoBi have different characteristics. In the structural change during water oxidation, CoBi is much more flexible compared to CoPi due to the larger change of bond distance of Co-O and Co-Co. In terms of the electronic structure shown by RXES analysis, CoBi clearly shows inter-site mixing, which is one of the factors for electron transfer in the inner domain but does not occur in CoPi. The higher intensity of Co(II) is shown in CoPi rather than CoBi at open circuit potential (OCP). Interestingly, both Co(II) features disappear and appear above and below water oxidation potential. Both systems also show a new feature which was assigned as Co(IV) by other people. The origin of the new feature will be explained by rigorous theoretical calculation. If time allows, the PDF/RIXS analysis of Iridium OECs will be presented.
Methanol Production By H2 Generated from Water Using Integrated Ultra High Concentrated Solar Cells-Electrolysis and Captured CO2: A Process Development and Techno-Economy Analysis
Authors: Isimjan Tayirjan Taylor , Idriss Hicham
Published: February 2020

A novel hybrid process based on an ultra-high concentrated solar module and water electrolysis for the production of methanol is presented. This process utilizes captured CO2 and H2 produced by electro-catalytic water splitting. The electrocatalytic system is powered by high concentration photovoltaic modules during the day and from an electrical grid during the night. The system is called the Hybrid High Concentration Solar and Electrolyzer system (HHCSE). Aside from the highly concentrated photovoltaic (UHC-PV) water splitting unit, which is currently under development, the full system is based on well-established industrial processes and component designs. Here, we present an initial assessment of energy efficiency and economic viability of a 233 tonne/day industrial-scale methanol plant. The breakeven price of the methanol produced using the base case is 0.62 $/kg. A levelized selling price of methanol of less than 0.50 $/kg can be achieved using the integrated system with a solar to hydrogen efficiency (STH) of 30% which is comparable to the current market price (0.510 $/kg). For the base case with STH (20%), the price of electricity (0.05 $/kWh) and location in Tabuk, Saudi Arabia, the gross energy efficiency of the process is 18%. Importantly, the primary economic driver is the high capital cost of the H2 production plant associated with the solar concentrator unit. The electrocatalytic system and solar concentrators account for more than 83% of the hydrogen section capital expenditure. Moreover, the electricity price also has a significant effect on the final price of methanol. The analysis indicates that an alternate pathway of concentrated solar and electrolysis to fuels has significant potential. The sensitivity study points towards future research opportunities to increase STH of the solar modules, reduce the balance of system (BOS), and reduce the electricity cost to achieve lower priced methanol. As a final element, we compared the proposed process with other renewable methanol production routes from the literature to highlight the differences in electrochemical, photoelectrochemical and thermochemical approaches.

Figure 1
Photocatalytic Overall Water Splitting: Observing H2 and O2 Transients with Ni/NiOx-Modified Mg:SrTiO3
Authors: Mei Bastian Timo , Han Kai , Mul Guido
Published: February 2020

SrTiO3 is a promising semiconductor driving photocatalytic overall water splitting (POWS) under UV light illumination. Improving the performance of SrTiO3 in decomposing water into H2 and O2 can be achieved by introducing feasible co-catalyst, such as Pt or Ni/NiOx. Though co-catalysts are employed in heterogeneous photocatalysis engineering of semiconductor/co-catalysts interfaces is rarely reported in literature [1]. In addition, limited attention has been paid to structural/electronic changes of co-catalysts during illumination/reaction and transients occurring in hydrogen and/or oxygen evolution are barely discussed.

In this contribution the photocatalytic performance of SrTiO3-based systems will be analyzed using a Continuously Stirred Tank Reactor (CSTR) connected to a micro GC-PDD (Pulsed Discharge Detector). Due to the favorable time-resolution of the GC-PDD transients in the evolution of H2 and O2, especially in the initial stages of testing, can be easily revealed. We will highlight the following recent observations:

For Ni/NiOx-modified SrTiO3, severe changes in the oxidation state of NiOx assigned to the transformation of Ni(OH)2 to NiOOH leading to an active photocatalyst/co-catalyst material in agreement with transient H2 evolution will be discussed [2];

Electronic modification of SrTiO3 by Mg incorporation into the perovskite structure can be obtained by a simple solid-state preparation [3]. While significant improvements in the steady state photocatalytic efficiency are obtained (Fig. 1), we also observed drastic changes in the initial transients caused by the interaction of Mg and Ni/NiOx;

Finally, it will be highlighted that stabilization of the Ni/NiOx-modified Mg:SrTiO3 photocatalyst is obtained by photodeposition of CrOx from Cr(VI) containing solutions [4]. Enhanced stability is probably caused by electronic modification of Ni/NiOx as a severe influence of the back reaction of H2 and O2 was not observed for the process conditions used.

Finally, the general stability of SrTiO3 in aqueous environment will be discussed.

Thus, using state-of-the-art micro-GC analysis we were able to design a stable composite photocatalyst and improve the efficiency of the system (AQE) from 0.6% to >40%.

References

[1] B. Mei, K. Han, G. Mul, ACS Catal., 2018, 8, 9154-9164; [2] K. Han, T. Kreuger, B. Mei, G. Mul, ACS Catal., 2017, 7, 1610-1614; [3] K. Han, Y. Lin, C. Yang, R. Jong, G. Mul, B. Mei, ChemSusChem, 2017, 10, 4510 – 4516. [4] K. Han, B. Mei, et al., to be submitted
Pt-Zn Nanocube for Enhanced Mass and Specific Activities in Ammonia Electro-Oxidation Reaction (AOR)
Authors: Shao Minhua , Chan Yat Tung
Published: February 2020

Many studies have revealed that only platinum and iridium can selectively oxidize ammonia to nitrogen, as the two combines a good dehydrogenation capacity with a sufficiently low affinity for the poison Nads [1]. While platinum is expensive, one effective approach to reduce platinum loading and increase catalytic activity is alloying platinum with other metals and forming binary or ternary alloys. In one research, Jiang [2] introduced zinc into platinum and iridium electrode by electrodeposition and demonstrated an increase of ammonia electro-oxidation reaction (AOR) catalytic activity.

In this study, Pt-Zn cubic nanoparticles were synthesized and loaded onto carbon black. The shape of Pt-Zn nanoparticles was mostly cubic illustrated by TEM images and the atomic ratio of Pt to Zn was around 4 to 1 according to ICP-OES. These Pt-Zn nanoparticles exhibited an improvement in AOR activity compared with cubic Pt nanoparticles and commercial Pt nanoparticles normalized to ECSA, termed specific activity, as shown in figure 1. The AOR peak current of Pt-Zn nanoparticles specific activity was 2.15*10-3 A/cm2 which is 1.1 and 17.1 times higher than cubic Pt and commercial Pt nanoparticles respectively. The possible reasons for increase of AOR activity will be discussed in detail.

Reference

[1] A. C. A. de Vooys, M. T. M. Koper, R. A. Van Santen and J. A. R. Van Veen, J. Electroanal. Chem., 2001, 506, 127–137.

[2] J. Jiang, Electrochemistry Communications, 75 (2017) 52-55.

Figure 1
(Invited) Plasmon Resonant Photocatalysis Via Hot Electron Injection
Authors: Cronin Stephen B.
Published: February 2020

Plasmon resonant grating structures provide an effective platform for distinguishing between the effects of plasmon resonant excitation and bulk metal absorption via interband transitions. By simply rotating the polarization of the incident light, we can switch between resonant excitation and non-resonant excitation, while keeping all other parameters of the measurement constant. With light polarized perpendicular to the lines in the grating (i.e., TE-polarization), the photocatalytic reaction rate (i.e., photocurrent) is measured as the angle of the incident laser light is tuned through the resonance with the grating. Here, hot holes photoexcited in the metal are used to drive the oxygen evolution reaction (OER), producing a measurable photocurrent. Using TE-polarized light, we observe sharp peaks in the photocurrent and sharp dips in the photoreflectance at approximately 9o from normal incidence, which corresponds to the conditions under which there is good wavevector matching between the incident light and the lines in the grating. With light polarized parallel to the grating (i.e., TM), we excite the grating structure non-resonantly and there is no angular dependence in the photocurrent or photoreflectance. In order to quantify the lifetime of these hot carriers, we performed transient absorption spectroscopy of these plasmon resonant grating structures. Here, we observe one feature in the spectra corresponding to interband transitions and another featured associated with the plasmon resonant mode in the grating. Both features decay over a time scale of 1-2 psec. The spectral responses of grating structures fabricated with Ag, Al, and Cu are also presented.

References:

Hou, B.Y., L. Shen, H.T. Shi, R. Kapadia and S.B. Cronin, Hot electron-driven photocatalytic water splitting. Physical Chemistry Chemical Physics, 19, 2877-2881 (2017).

Shen, L., N. Poudel, G.N. Gibson, B. Hou, J. Chen, H. Shi, E. Guignon, W.D. Page, A. Pilar and S.B. Cronin, Plasmon Resonant Amplification of a Hot Electron-Driven Photodiode. Nano Research, DOI: 10.1007/s12274-017-1854-2 (2017).

Shen, L., G.N. Gibson, N. Poudel, B. Hou, J. Chen, H. Shi, E. Guignon, W.D. Page, A. Pilar and S.B. Cronin, Plasmon Resonant Amplification of Hot Electron-Driven Photocatalysis. Applied Physics Letters, DOI: 10.1063/1.5048582 (2018).

Figure 1
Mechanistic Control of the Galvanic Replacement Reaction of Gold on Cuprous Oxide
Authors: Lowe James Michael , Coridan Robert
Published: February 2020

Galvanic replacement (GR) reactions are a versatile approach to fabricating hierarchically structured functional nanomaterials for catalytic, plasmonic, and sensing applications. Most research efforts aim to identify chemical strategies to control the resultant morphology of GR deposition on metallic nanoparticle seeds. Recently, GR has become a method of interest for fabricating heterogeneous interfaces for these applications. In this talk, we will discuss the chemical mechanism for the GR reaction of AuCl4
- on Cu-based thin films. X-ray photoelectron spectroscopy and structural characterization show that, while the GR reaction proceeds through the direct dissolution of Cu and reduction of AuCl4
- on Cu, the reaction of Cu2O results in the solid-state formation of CuO at the interface. The GR reaction does not continue on the CuO substrate. As a result, the chemistry and morphology of Au deposited on Cu2O is limited by the rate of CuO dissolution in the background acidic electrolyte. We propose a mechanism for the GR reaction on Cu2O surfaces where disproportionation is the limiting intermediate reaction which can be mediated by AuCl4
- concentration and by the photoelectrochemical generation of Cu nanoparticles throughout the bulk of the Cu2O. Consequently, the hierarchical structure of the GR deposition of Au can be chemically controlled on Cu2O films. More generally, this highlights how the details of the chemical kinetics at the reaction interface can be exploited to tailor the resulting nanostructure of metals deposited via GR reactions.
(Keynote) A High Performance Tubular Solid Oxide Fuel Cell for Unmanned Autonomous Systems
Authors: Chu Deryn , Chu Kevin , Cook Clifford , DeAnni Anthony
Published: February 2020

Currently, the flying ability for small autonomous unmanned aerial systems (sUAS) is limited by both power and energy. We have selected, developed and examined several cutting-edge power and energy technologies to power sUAS. Currently, sUAS are powered by small engine generators that generate lots of noise and pollutants or advanced batteries – which cannot sustain a long endurance operations. Additionally, polymer electrolyte membrane fuel cells still have the same technical constraints, the source of hydrogen, as it did many years ago. We have examined and believe the operational capabilities of solid oxide fuel cell (SOFC) technology can power an sUAS. A propane fueled high power density tubular SOFC has been developed for autonomous UAS. A self-sustaining miniature tubular SOFC stack provides a unique high power and high energy density for UAS. A tubular SOFC stack has been evaluated and tested, and its performance meets the requirements for a sUAS system. The SOFC has great potential for commercial and civilian applications, ranging from small scale systems (e.g. small unmanned air vehicle, wireless sensor networks) to large scale system (e.g. electric vehicle, wireless sensor networks, electric vehicles).
(Invited) Development of High Performance Non-PGM Electrocatalysts and Electrodes for the Oxygen Reduction Reaction in Aemfcs
Authors: Peng Xiong , Kashyap Varchaswal , Kurungot Sreekumar , Mustain William E.
Published: February 2020

Anion exchange membrane fuel cells (AEMFCs) have received significant attention in recent years as a potentially lower cost electrochemical energy conversion device compared to proton exchange membrane fuel cells (PEMFCs) [1]. In the past few years, several achievements have been made in terms of single cell performance, including power densities comparable to PEMFCs (~ 1.9 W cm-2)[2–4], and stability over hundreds of hours of operation[5,4], which are critical to the development and future deployment of AEMFCs. However, to make AEMFCs more economically competitive, or even favorable, with PEMFCs, it is crucial to discover non-PGM electrocatalysts for both the oxygen reduction reaction (ORR) and hydrogen oxidation reaction in AEMFCs that are able to achieve high power densities and long term operation.

Over the last decade, significant progress has been made in finding PGM-free catalysts for the ORR in alkaline media. However, an overwhelming majority of the tests with these materials have been done ex-situ using rotating disk electrodes (RDE), and these measurements and are not typically representative of the in-cell performance due to more complicated mass transport and reacting conditions. Hence, many highly active ex-situ catalysts have shown limited performance in operating AEMFCs. In this work, we studied two types of non-PGM electrocatalysts, including CoOx embedded in nitrogen-doped carbon (CoOx-N-C)[6] and classical Fe-N-C, for the ORR in AEMFCs. Not only was the ORR activity fully characterized using RDE and RRDE measurements, with both catalyst exhibiting excellent half-cell activity, but they were also incorporated into gas diffusion electrodes and studied in 5 cm-2 single cell AEMFCs. This study was able to show that PGM-free electrodes are able to support high performance (> 1.0 W cm-2), achievable current density and stability (>100 h). This work demonstrates a significant improvement in non-PGM electrocatalysts development and performance than previous work.

Reference:

[1] J. R. Varcoe, P. Atanassov, D. R. Dekel, A. M. Herring, M. A. Hickner, P. A. Kohl, A. R. Kucernak, W. E. Mustain, K. Nijmeijer, K. Scott, et al., Energy Environ. Sci.
2014, 7, 3135–3191.

[2] L. Wang, E. Magliocca, E. L. Cunningham, W. E. Mustain, S. D. Poynton, R. Escudero-Cid, M. M. Nasef, J. Ponce-González, R. Bance-Souahli, R. C. T. Slade, et al., Green Chem.
2017, 19, 831–843.

[3] T. J. Omasta, L. Wang, X. Peng, C. A. Lewis, J. R. Varcoe, W. E. Mustain, J. Power Sources
2018, 375, 205–213.

[4] T. J. Omasta, A. M. Park, J. M. LaManna, Y. Zhang, X. Peng, L. Wang, D. L. Jacobson, J. R. Varcoe, D. S. Hussey, B. S. Pivovar, et al., Energy Environ. Sci.
2018, 11, 551–558.

[5] W. E. Mustain, Curr. Opin. Electrochem.
2018, 1–7.

[6] xiong peng, T. J. Omasta, E. Magliocca, L. Wang, J. R. Varcoe, W. E. Mustain, Angew. Chemie Int. Ed.
2018, 1–7.
Anion Exchange Membrane Fuel Cell Application of Synthesized Poly(ether ether ketone) Containing Imidazolium
Authors: Nam Sang Yong , Son Tae Yang , Ko Tae Ho , Kim Ki Hyun
Published: February 2020

The proton exchange membrane fuel cells, which have been extensively studied at present, have excellent performance but have a disadvantage of using expensive platinum catalysts. On the other hand, anion exchange membrane fuel cells have the advantage of using non-precious metal catalysts, and anion exchange membranes are a key component. An important component, anion exchange membranes, must have high electrochemical and mechanical properties. For the application of anion exchange membranes, poly(ether ether ketone)(PEEK) based copolymers containing imidazolium groups were synthesized. The synthesized PEEK had different contents of imidazolium group. To prepare the free standing films, PEEK containing various equivalents of imidazolium groups was dissolved in n-methyl-2-pyrrolidone (NMP). The films were then prepared with various PEEK solutions through a Petri dish and then the properties of the films were evaluated. The ion exchange capacity was measured by back-titration method and the ion conductivity was calculated by membrane resistance method. The TGA and UTM were used to investigate the thermal and mechanical properties of the various PEEK films.
Construction of NiMoO4/Polypyrrole Nanocomposites on Carbon Cloth As Advanced Electrodes for High Performance Flexible Supercapacitors
Authors: Zhu Di , Wang Jun
Published: February 2020

With the rapid development of new-generation flexible electronics, future power sources are required to be mechanically flexible and also have both high energy and large power as well as long cycle life. Flexible Supercapacitors have been widely investigated by the reasons of their excellent electrochemical performance such as high power delivery, operational safety, long cycle life and flexibility. Flexible electrodes, owing to their unique advantages like flexible and wearable, have drawn many attentions. However, there still exist some challenges to improve flexible electrode materials’ conductive property and excellent cycle stability. In this paper, NiMoO4/Polypyrrole (PPy)/carbon cloth (CC) flexible electrode is proposed, using a hydrothermal synthesis method and a chemical polymerization process, to solve these issues. The designed NiMoO4/PPy/CC electrode has following advantages: 1) the electrode is flexible, light weight, good electrical conductivity (PPy possesses higher conductivity which can ensure the conductivity of the materials). 2) the NiMoO4 nanowires can directly grow on the substrate without using any binders and provide a frame support for PPy nanoparticles cladding, which can effective reduce the charge-transfer resistance and shorten the path of ion diffusion and electron transport. 3) nanocomposites can directly provide the current channels and transfer the electrons more efficient. 4) the hybrid structure can prevent the electrode material’s damage from volume change in the charge-discharge process and prove the long cycle life. 5) the designed nanocomposites can take advantages of all good function of components and achieve a synergistic effect. So the electrode exhibits a high areal specific capacitance of 1.64 F cm-2 at a current density of 1mA cm-2 and capacitance retention 98.2% after 2000 cycles. The results showed that the NiMoO4/PPy exhibit remarkable electrochemical performance, which could be utilized as a promising pseudocapacitive electrode material for high performance flexible supercapacitors. (This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation.)

Figure 1
(Invited) Electro-Osmosis in Polymer Electrolytes
Authors: Zawodzinski Thomas A.
Published: February 2020

Among the contributions from the early work of the fuel cell group at Los Alamos, the development of a model of water transport in PEM Fuel Cells based on measured transport properties is one that has helped to spawn decades of research in fuel cell membranes. While studies and descriptions of membrane transport properties such as conductivity and diffusion, along with the underlying water uptake, are now commonplace, the decisive property of electro-osmosis is much less widely reported. In this talk, I will describe our early work in a historical and scientific context, including some speculation on the critical contributing interactions that help us to rationalize electro-osmotic drag. I will then proceed to update that work to include more recent work on migration-driven transport in other contexts, including alkaline exchange membrane fuel cells and redox flow batteries.

Acknowledgement

We gratefully acknowledge the support of this work by the US Department of Energy Fuel Cell Technology Office and its various preceding versions.
(Invited) Precious Metal-Free Electrocatalysis: Accomplishments and Challenges
Authors: Zelenay Piotr
Published: February 2020

In this short presentation, we will concentrate on entirely precious metal-free electrocatalysts as potential alternatives to the incumbent platinum group metal (PGM) materials for electrochemical reactions occurring in acidic, relevant to the energy conversion and storage: (i) oxygen reduction reaction (ORR), (ii) hydrogen evolution reaction (HER) and, time permitted, (iii) hydrogen peroxide generation (“two-electron ORR”). In the first part of this presentation, we will offer a summary of the development of non-precious metal ORR catalysts, emphasizing in particular the approaches that aim at improving the ORR active-site density and understanding of the origins of electrocatalytic activity of non-precious metal catalysts in oxygen reduction as a prerequisite for further development of this class of catalysts. We will focus on metal-nitrogen-carbon (M-N-C) catalysts obtained via the high-temperature treatment of organic precursors of carbon and nitrogen and inorganic precursors of a transition metal, which have been under development at Los Alamos for over a decade and have consistently exhibited the highest ORR activity in both electrochemical-cell and fuel cell testing to date.

The second part of this presentation will be devoted to less frequently studied electrocatalysts based on small organic molecules as materials for hydrogen evolution reaction and hydrogen peroxide generation in a two-electron ORR. Unlike the oxygen reduction reaction catalysts in the first part of the talk, these HER/two-electron ORR catalysts are entirely metal-free and have been obtained by a low-temperature synthesis route. In addition to exhibiting a promising activity in electrochemical testing these catalysts show good performance durability over several days of continuous operation. The density functional theory (DFT) calculations have been performed to gain an insight into the reaction mechanisms of HER and two-electron ORR on various conformations of one selected organic molecule. The calculations have revealed thermodynamically favorable reaction pathways and structure-activity relationships, which can guide future synthesis of this new class of electrocatalysts.

Acknowledgements

Financial support of this research by the U.S. Department of Energy via Fuel Cell Technologies Office (FCTO) and by Los Alamos National Laboratory via Laboratory Directed Research and Development (LDRD) program is gratefully acknowledged.
(Invited) Shape-Controlled Multimetallic Nanoparticle Electrocatalysts
Authors: Roldan Cuenya Beatriz
Published: February 2020

Alternatives to fossil fuels are actively being sought for the sustainable generation of energy with minimum environmental impact. Direct alcohol fuel cells are among the most promising clean energy supply devices. Nevertheless, the high cost and the low efficiency of the electrocatalysts difficult the commercialization of such devices. Thus, the replacement of Pt-based materials in fuel cells has received increasing attention over the past years.

In this talk I will describe the rational design of highly active and selective mono and multimetallic nanoparticle (NP) electrocatalysts with tunable exposed facets and composition. Examples include spherical Au NPs for 2-propanol oxidation, cubic Pt-Sn-Co NPs for ethanol oxidation and Pd cubes decorated with Cu and Sn for methanol and ethanol oxidation. Valuable mechanistic insights were obtained by combining different in situ spectro-electrochemical techniques and operando synchrotron methods, such as differential electrochemical mass spectrometry, Fourier-transformed infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption fine-structure spectroscopy.
(Invited) Materials/System Tradeoffs for Automotive Fuel Cell Applications
Authors: Gittleman Craig S , Kongkanand Anusorn
Published: February 2020

Recent focus on materials R&D for proton exchange membrane fuel cells for automotive applications has been on lower cost materials such as non-PGM catalysts and non-fluorinated membranes. Other areas of focus have been on materials that can withstand specific failure modes, such as non-carbon supports that can withstand elevated potentials experienced during non-mitigated start-stop conditions. These materials, in nearly all cases, do not perform as well as Pt or Pt-alloy catalysts supported on high surface area carbons with perfluorinated membranes. This could lead to the incorporation of larger stacks, and therefore, more expensive systems.

This talk will focus on the system materials trade-offs that OEMs must consider when developing automotive FC systems. When designing a system, all high-level requirements including cost, performance, durability and robustness, must be considered. Performance metrics must include power density, efficiency and heat rejection. Power density and heat rejection and driven by high current density performance whereas efficiency is driven more by low current density performance. Durability issues include voltage degradation as well as failures that prevent a system from operating safely such as severe membrane crossover. Some of these metrics can be directly translated into cost. For example, power density and voltage degradation can be combined into an end-of-life power density requirement. This requirement can often be “bought” by adding more Pt. Other metrics, such as efficiency, time to membrane failure and robustness are less easy to “buy”.

This talk will discuss the materials trade-offs to optimize automotive fuel cell system requirements. We will discuss the how to determine the optimum Pt loading to minimize system cost. We will also discuss the trajectory and potential for non-PGM catalysts to reduce automotive fuel cell system costs. We will discuss the trade-offs regarding membrane thickness, where thinner membranes promote higher power density but reduced efficiency due to greater H2 crossover. We will discuss the tradeoffs for corrosion resistance catalyst supports, which are being developed to prevent degradation during start-start environments, but due to their inherent lower surface area and electrical conductivity ultimately limit fuel cell performance. There are system mitigation strategies that can be employed that may be less expensive than the added cost of a larger stack required to meet power density requirements. We will also discuss how all of these materials developments impact durability.
(Invited) Modeling of Carbon Dioxide Exposure and Mitigation in Hydroxide Exchange Membrane Fuel Cells
Authors: Setzler Brian P. , Shi Lin , Wang Teng , Yan Yushan
Published: February 2020

Despite rapid advancements in performance and durability of hydroxide exchange membrane fuel cells (HEMFCs), the performance loss caused by carbon dioxide in air is unacceptable for transportation applications1. In this paper an expanded model2 of carbon-dioxide-induced performance loss will be presented. The model predicts performance loss under dynamic and steady-state conditions, considering effects of temperature, carbon dioxide concentration, fuel and air stoichiometry, anode recycle, and down-the-channel concentration gradients.

There are two major causes of performance loss upon CO2 exposure: lowered anode pH and reduced ionic conductivity. CO2 reacts with hydroxide to form carbonate and bicarbonate, which are pushed to the anode by the ionic potential gradient. At the anode, these anions accumulate, lowering the pH. At a sufficiently low anode pH, bicarbonate decomposes, establishing a steady state. The pH gradient shifts the half-cell potentials of the anode and cathode reactions, which reduces the cell voltage by an amount that depends on the transference number of hydroxide, but can be approximated as 70 mV per pH unit over most of the pH range. Accumulation of bicarbonate also causes an increase in Ohmic losses due to reduced ionic conductivity, but this effect is generally secondary to the concentration polarization caused by the pH gradient.

The anode pH is determined primarily by the kinetics or thermodynamics of bicarbonate decomposition, which in practice, means that even very high values of ionomer conductivity cannot mitigate the performance loss under CO2. Figure 1 shows the modeled performance loss caused by 400 ppm CO2 in air for HEMFCs with ionomer hydroxide conductivity values of 5-40 S/m. Except at very low current density, increasing hydroxide conductivity does not render the HEMFC less sensitive to CO2.

Figure 2 shows the transient performance loss caused by CO2 uptake at 1 A/cm2 and a range of CO2 concentrations from 0.1 to 10 ppm. At 1 ppm, performance drops by 10 mV in the first 0.5 h and 30 mV at steady state. Even at 0.1 ppm, the modeled performance loss is 10 mV at steady state. These simulations provide a first indication of the level of CO2 removal required for systems operating on air and should be supplemented with experimental measurements.

The model results lead to the disappointing conclusion that a CO2-tolerant HEMFC cell is unlikely. However, modeling also supports the viability of CO2 removal using electrochemical pumping, which could be significantly more compact and less costly than conventional scrubbing. Proof-of-concept experiments will be presented, and future prospects will be discussed.

References

S. Gottesfeld et al., J. Power Sources, 375, 170–184 (2018).

B. P. Setzler and Y. Yan, Meet. Abstr. , MA2017-01, 1654 (2017).

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(Invited) Anion Exchange Membranes Based on Functionalized Block Copolymers
Authors: Yandrasits Michael , Laskowski Carl , Gillard Tim , Kurkowski Michael , Lindsay Maria , Pivovar Bryan S. , Owczarczyk Zbyslaw R.
Published: February 2020

Anion exchange membranes (AEMs) have the potential for use in electrochemical devices such as fuel cells, electrolyzers, and flow batteries. In order to compete with well-established perfluorosulfonic acid (PFSA) based proton exchange membranes (PEMs), AEMs will have to demonstrate high anion conductivity, excellent durability, and acceptable costs. We aim to apply the learnings gained from years of experience with PFSA ionomers to develop new, block copolymer, AEMs with these properties. The goal of this approach is to make multi-block copolymers containing polyethylene and cationic functional segments. The strategy is to start with a poly(1,4 butadiene-block-1,2 butadiene-block-1,4 butadiene) and selectively functionalize the 1,2 butadiene block to form a side-chain amine followed by hydrogenation of the 1,4 block to yield the polyethylene segment. In addition, penta-block structures that include styrene segments have been developed. In either case, the “soft-block” segments are functionalized while the “hard-block” segments are retained. The polyethylene backbone is expected to impart excellent mechanical properties and stability in high pH environments. Membranes fabricate with these techniques have been evaluated for conductivity, water uptake, mechanical properties, and stability to hydroxide ions.
(Invited) Stable and Conductive Anhydrous Proton Conducting Membranes Based on Polycations Blended with Polybenzimidazole
Authors: Arges Christopher George , Venugopalan Gokul , Kole Subarna
Published: February 2020

This talk primarily focuses on anhydrous, mild temperature (100 to 250 °C) proton conductors composed of polycation polymers, typically used as anion exchange membranes, blended with polybenzimidazole (PBI). These moderate temperature membranes are envisioned for fuel cell systems that operate with hydrogen from steam-reformed methane. Evaluating polycation membrane variants alone demonstrated lower proton conductivity when compared to PBI doped with phosphoric acid (H3PO4) and sulfuric acid. PBI doped with phosphoric acid, on the other hand, was observed to be unstable above 160 °C because of H3PO4 boiling and evaporation. Plus, the PBI-H3PO4membrane loses its acid due to leaching if condensed water is present (i.e., lack of robust operation if the cell drops below 100 °C).

To overcome these problems, polycation polymers, were blended with polybenzimidazole (PBI) and these membranes routinely showed conductivity values as high as 0.18 S cm-1and were stable under dry and wet conditions and with thermal stability up to 250 °C. These membrane composites were also assessed with other types of doped acids (e.g., phosphoric acid, methanesulfonic acid, p-toulenesulfonic acid, trifluoroacetic acid, and sulfuric acid) to promote the Faradaic reaction kinetics at low pH (i.e., pH values below 0).

The talk will close with our recent efforts to pattern polymer electrolyte membrane surfaces to make high surface area bipolar junction interfaces. It is envisaged that an acidic anode and alkaline cathode with a bipolar membrane offers a pathway forward for very low platinum loading fuel cells.

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Electrochemistry of Antibiotic Hybrids: Towards the Detection and Quantification of Antibiotic Resistance
Authors: Kuss Sabine , Islam Rafiqul MD , Sahihi Mehdi , Schweizer Frank
Published: February 2020

The overuse of antibiotics in human and veterinary medicine as well as in agriculture has caused antibiotic resistance to become a global problem and national and international health organizations have called for the urgent development of new treatment strategies. The increase of antibiotic resistance in Gram-negative bacteria in particular is a major cause for concern, as many Gram-negatives cause serious infections, such as pneumonia, and only few effective antibiotics have been developed due to bacterial innate defense mechanisms, including low outer membrane permeability and high number of efflux pumps. The presented study demonstrates the thorough electrochemical characterization of antibiotic hybrid drugs, currently under development at the University of Manitoba, Canada. The interaction of these antibiotic hybrids with selected biomolecules is investigated to further our understanding about in vivo processes of drug absorption, distribution, metabolism, and excretion. Furthermore, the interaction of bacteria with the newly developed investigational antibacterial therapeutics is studied towards the quantification of antibiotic resistance in pathogens to address the dire need for innovative strategies that are able to quantify efflux and influx of agents into bacterial cells for the assessment of potential new and reliable antimicrobial candidates.
Bio-Inspired Nanowire Arrays As Artificial Photoreceptors for Retinal Prosthesis
Authors: Tang Jing
Published: February 2020

The restoration of light response with complex spatiotemporal features in retinal degenerative diseases towards retinal prosthesis has proven to be a considerable challenge over the past decades. Herein, inspired by the structure and function of photoreceptors in retinas, we develop artificial photoreceptors based on gold nanoparticle-decorated titania nanowire arrays, for restoration of visual responses in the blind mice with degenerated photoreceptors. Green, blue and near UV light responses in the retinal ganglion cells (RGCs) are restored with a spatial resolution better than 100 µm. ON responses in RGCs are blocked by glutamatergic antagonists, suggesting functional preservation of the remaining retinal circuits. Moreover, neurons in the primary visual cortex respond to light after subretinal implant of nanowire arrays. Improvement in pupillary light reflex suggests the behavioral recovery of light sensitivity. Our study will shed light on the development of a new generation of optoelectronic toolkits for subretinal prosthetic devices.

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