bluuebunny/crossref_metadata_2025 huggingface dataset:
Layered Perovskite Electrodes with High Performance and Durability for Solid Oxide Electrolysis
Authors: Jun Areum , Kim Guntae
Published: February 2020

In recently years, there has been a robust attention in clean and renewable energy sources due to heavy dependence on finite fossil fuels as our major source of energy, causing serious energy and environmental crisis such as emission of CO2 and NO
x
on the world. Hydrogen is attracted as a leading candidate for alternative future fuels because it has the potential to address the environmental and energy security issues associated with fossil hydrocarbon fuels. Solid oxide electrolysis cells (SOECs) are one of the promising technology for the efficient production of H2 from electricity because electrolysis at elevated temperatures is beneficial for both thermodynamic and kinetic reasons. Recent significant interest in steam electrolysis has been mainly concerned with performance, durability and degradation issues. In conventional SOE used for steam electrolysis, the most commonly used cathode and anode materials for oxide ion-conducting SOECs are Ni-YSZ (yttria-stabilized zirconia) and LSM (strontium-doped lanthanum manganites)-YSZ, respectively. But, these electrode materials suffer from several problems such as an intrinsic redox instability, agglomeration and coarsening of nickel particles for Ni-YSZ and a delamination and insufficient durability of LSM-YSZ during steam electrolysis. In this study, the layered perovskite oxides employed as potential ceramic cathode and anode for SOEC with dense LaGaO3 based electrolyte, showing a high performance and durability over 600 hours with no degradation in electrolysis mode.
Performance Evaluation of Solid Oxide Carbon Fuel Cells Operating on Steam Gasified Carbon Fuels
Authors: Lim Tak-Hyoung , Lee Jong-Won , Lee Seung-Bok , Park Seok-Joo , Song Rak-Hyun
Published: February 2020

We investigated the operating characteristics of solid oxide carbon fuel cells (SO-CFCs) integrated with a steam gasifier that used carbonaceous fuels, including activated carbon and biomass driven charcoal. Steam gasification was carried out in a specially designed gasifier, which was directly integrated with a solid-oxide based carbon fuel cell. We studied the effect of gasification temperature, steam flow rate and catalyst addition on the electrochemical performance of SO-CFC, and the results showed that among the three tested fuels, activated carbon with a K2CO3 catalyst performed the best. At 850°C, the maximum power density 108mW/cm2, 161mW/cm2 and 181mW/cm2 was achieved when the SO-CFC operated on activated carbon, biomass driven charcoal and activated carbon with a K2CO3 catalyst, respectively. The SO-CFC operated continuously for 100h and it showed relatively stable performance. This study suggests that by using a catalytic steam gasifier integrated with the SO-CFC, the solid carbon fuel resources can be used for power generation with higher efficiency and minimal carbon footprint.
La-Doped BaSnO3 As Anode Material for Low Temperature-Solid Oxide Fuel Cells
Authors: Abdul Jabbar Mohammed Hussain , Robinson Ian , Pan Ke-Ji , Wachsman Eric D
Published: February 2020

Barium stannate doped with 2 at.% of lanthanum was synthesized and investigated as a potential anode material for low temperature solid oxide fuel cells (LT-SOFCs). Ba0.98 La0.02SnO3-δ ceramic was calcined at 1200-1300°C in air to obtain the cubic perovskite phase and then sintered at 1550°C for 12h. The sintered sample has shown approx. 7% shrinkage and 70% density.  For the 30% porous sample, electrical conductivity values of 8.7 S/cm and 9.3 S/cm, respectively was achieved, at 600°C and 400°C, respectively in 10% H2/3%H2O/N2.The preliminary results has shown a decent redox stability, approx. 7 % loss in conductivity at 600°C when cycled 3 times between air and reducing conditions over a period of 60 h. Post-test XRD analysis on Ba0.98 La0.02SnO3-δ samples show structural stability by retaining the cubic perovskite phase. The material was also stable in dry and humidified H2. Interestingly, the material has shown semi-conductor like behavior in the presence of methane. The conductivity values of the materials in 97%CH4/3%H2O gas were 6.4 and 2.2 S/cm at 600 and 500°C, respectively. This material has promising performance for integration into an LT-SOFC anode, but processing challenges remain.
(Invited) Oxygen Evolution Catalysts for Water Electrolysis: Challenges and Progress with Extended Surface Ir-Based Catalysts
Authors: Alia Shaun M , Hurst Katherine , Neyerlin K.C. , Kocha Shyam S. , Ngo Chilan , Shulda Sarah , Pylypenko Svitlana , Pivovar Bryan S
Published: February 2020

Electrolysis is near parity as an energy storage process when compared to the cost of competing technologies, including batteries, pumped hydro, and compressed air.[1] When coupled with renewable energy sources, such as wind and solar, electrochemical water splitting can also produce hydrogen using a nearly carbon free pathway.[1]  Some overview content will be presented to provide justification for decreased capital costs in electrolyzers as well as focus on aspects of intermittent operation.  An operational mode not used typically today in electrolysis, but one that will become of higher interest in the future with increasing renewable energy penetration and growing hydrogen markets.

Iridium nanoparticles are commonly used as electrocatalysts in acidic electrolyzers due to moderate stability and activity in the oxygen evolution reaction (OER). Baseline materials and protocols are still being developed to benchmark the current status of OER catalysts.  The presentation will discuss results along these lines, as well as discuss mercury underpotential deposition as a method for determining surface area for iridium and/or iridium oxide.

Progress made at NREL on Ir based nanowires for OER that leverage off of previous experiences in the production of Pt based nanowires for oxygen reduction reaction [2] will also be presented.

References

[1] K. Harrison, M. Peters, in: U.S. Department of Energy (Ed.), http://www.hydrogen.energy.gov/pdfs/review13/pd031_harrison_2013_o.pdf, 2013.

[2]  S.M. Alia, Y. Yan, B.S. Pivovar, “Galvanic Displacement as a Route to Highly Active and Durable, Extended Surface Electrocatalysts” Catalysis Science and Technology, 2014, 4 (10), 3589 - 3600.
Durable Membrane Electrode Assemblies (MEA) for Proton Exchange Membrane (PEM) Electrolyzer Systems Operating at High Current Densities
Authors: Lettenmeier Philipp , Wang Rainey , Abouatallah Rami , Gago Aldo Saul , Friedrich K. Andreas
Published: February 2020

Hydrogen can be used as an energy vector for renewable energies such as solar or wind by using water electrolysis systems [1]. Commercially, it can be electrochemically produced by alkaline and proton exchange membrane (PEM) electrolysis, at which the investment cost of the later is presently almost three times higher than the alkaline technology [2]. However, the main advantage of PEM electrolysers is the possibility to operate at much higher current densities with a significant potential for cost reduction owing to the compact design [3]. An open question is still the life time of the membrane electrode assembly (MEA) of the PEM electrolyser operating at high performance. In this work rainbow stacks with MEAs from different suppliers are tested in a 20 kW PEM electrolyser (2.5 N m³ H2 h-1) operating constantly and dynamically up to 5 A cm-2. The 120 cm2 active area MEAs have membranes with the same thickness but different Ir-based catalyst loadings. Operating the electrolyser at low current densities has an impact in the H2 crossover. The most durable MEAs do not experience any lost in performance after more than 3000 h of operation under stationary and dynamic regimes. Post-mortem characterisation and water analysis are carried out to determine the degradation mechanism of the rest of the MEAs.

References

[1]         A. Sternberg, A. Bardow, Energy Environ. Sci. (2015) 389.

[2]         Fuel Cells and Hydrogen Joint Undertaking, Report: Commercialisation of Energy Storage in Europe, 2015.

[3]         M. Carmo, D.L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy 38 (2013) 4901.
Self-Terminated Electrodeposition of Ultrathin Iridium Film Catalysts
Authors: Ahn Sang Hyun , Tan Haiyan , Liu Yihua , Bendersky Leonid A. , Moffat Thomas P.
Published: February 2020

Self-terminated electrodeposition process is used to grow ultrathin catalytic iridium (Ir) films. With a simple potential pulsing method, semi-coherent Ir films are deposited on various substrates in K3IrCl6-Na2SO4 electrolytes at the temperature range between 40 °C and 70 °C. The electrochemical reduction of IrCl6-x·H2Ox
3-x to Ir is quenched at the onset potential of hydrogen evolution reaction, even though the deposition overpotentials exceed 1.0 V because the deposited Ir surfaces are immediately passivated by H adsorption which can prevent the further Ir deposition. However, the deposited Ir film surfaces are reactivated toward further electrochemical reduction of IrCl6-x·H2Ox
3-x to Ir when the potential is rapidly changed to positive value where the adsorbed H is oxidized. After 1 deposition pulse, the X-ray photoelectron spectroscopy (XPS) derived Ir thickness is 0.085 ± 0.028 nm based on uniform overlayer model which is mostly independent deposition time. With repeated potential pulses, the XPS derived Ir thickness is increased from 0.343 ± 0.012 nm (2 deposition pulses) to 3.143 ± 0.083 nm (10 deposition pulses). The Ir coverage determined by H under potential deposition (HUPD) approaches a monolayer coverage after 3 deposition pulses. The various combination of Ir-based ultrathin films prepared self-terminated electrodeposition demonstrate high activity for hydrogen catalysis in alkaline and oxygen catalysis in acid.
Split Water Under 0.8 V at Room Temperature
Authors: Chen Xiaobo
Published: February 2020

Electrochemical water splitting normally requires a voltage between 1.6 and 2.5 V, due to the thermodynamic requirement (1.23 V at 25 °C), ohmic resistance and overpotentials on the anode and cathode. Here, we demonstrate a new concept that successfully splits water into oxygen and hydrogen at a voltage as small as 0.8 V at room temperature (25 °C) with earth-abundance catalysts. This concept breaks the thermodynamic requirement for water splitting and provides a bright future for the hydrogen economy.
N-Doped Reduced Graphene Oxide Composites for Hydrogen Generation in Presence of Chloride Ion Impurities in Alkaline Medium
Authors: Halder Aditi , Bharadwaj Arpit , Kushwahab Himmat Singh , Saquib Mohammad
Published: February 2020

The depletion in fossil fuel reserve leads to the search for a clean, alternate fuel which can replenish the energy demand without causing greater harm to the environment. Hydrogen is one such kind of promising sustainable energy fuel which can be produced from very cheap resources like water. The major hurdle behind the efficient and economical production of hydrogen through electrochemical conversion of water is the large thermodynamic overpotential related to it. Enormous volume of researches has been carried out towards the development of catalysts, improving support materials efficiency and electrochemical environment related to hydrogen evolution reaction (HER).

In this work we are going to present a catalyst which shows appreciable enhancement in the electrochemical activity towards HER in alkanine medium and can withstand very high chloride ion impurities in operating conditions. Often, the performance and durability of a fuel cell are greatly influenced by the presence of impurities present in the feed stock, air stream or other components of fuel cell. Among the different contaminants chloride (Cl-) ion is one of the serious impurities which can diffuse through the gas diffusion system and can poison the electrocatalysts and membrane and ultimately leads to the decrease performance of the fuel cell system. Hence it is important to develop a robust catalyst which will have dual functionalities. Along with enhanced performance, it also should be able to withstand the extreme poisoning effect during hydrogen evolution reaction.

In comparison to un-doped reduced graphene oxide (RGO)–Pt composites and commercial Pt /C catalysts, the nitrogen-doped graphene oxide (NGO)-Pt composites show low overall potential towards HER both in acidic and alkaline environment. Electro-catalytic performance of the prepared cathodes has been investigated by hydrogen evolution reaction in 0.1M perchloric acid, 0.5 M sulfuric acid and 0.1molar KOH solution. The controlled exposure of chloride ion impurities shows under similar condition NGO-Pt shows better stability and less reduction of electrochemical surface area (ESA) and hence less susceptible towards chloride poisoning under identical conditions. The loss of electrochemical surface area (ESA), before and after chloride poisoning, is much less in case of NGO-Pt . Figure 1 shows the comparison between the RGO-Pt,commercial-Pt and NGO-Pt for loss of ESA.

Figure 1
(Invited) Computational Design of Coatings, Interfaces, and Nano-Structures for Si Based Electrodes
Authors: Qi Yue , Kim Sung-Yup , Kim Kwang Jin
Published: February 2020

The chemical composition and mechanical properties change of coating materials, interfaces, and Si itself during lithiation and delithiation process imposed a grand challenge to design coating/Si nanostructure as an integrated electrode system. In our work, reactive force field (ReaxFF) parameters for Li-Si-Al-O-F were developed along with a new algorithm to simulate lithiation and delithation processes with different rates. With the reactive dynamics simulations, we were able to simultaneously track and correlate the lithiation-delithiation rate, compositional change, mechanical property evolution, stress distributions, and fracture. Interesting insights were obtained from these studies. For example, it was found that the lithiation rate during the initial mixing stage increases exponentially with vacancy concentrations in Si; and it was discovered the self-accelerating Li diffusion in Al2O3 coating forms a well-defined Li concentration gradient, leading to an elastic modulus gradient, which effectively avoids local stress concentration and mitigates crack propagation.  A new mechanics model based on these varying properties was developed to determine how to stabilize the coating with a critical size ratio.
A Multiphysics Study of Chemical Potential Distributions As Drivers for Solid Oxide Cell Mechanical Degradation
Authors: Nelson George J. , van Zandt Zachary
Published: February 2020

Solid oxide cells are promising energy conversion devices that enable the generation of power from diverse fuel sources in fuel cell operation and the production of hydrogen and syngas fuels when operating as electrolyzers. Accelerated degradation has been observed for electrolytic operation in comparison to fuel cell operation. Of particular note, oxygen electrode delamination has been observed for solid oxide electrolyzers. It has been proposed that this mechanical failure mode arises from adverse gradients in the oxygen chemical potential across the electrode-electrolyte interface. A multiphysics model of solid oxide cell operation has been developed for mass and charge transport in the presence of a distributed electrochemical reactions. Both 1D and 2D transport within the cross-section of a planar positive electrode-electrolyte-negative electrode (PEN) unit cell are addressed. Mass transport in the porous composite electrodes is treated using the dusty-gas model. Charge transport is cast in terms of ion and electron electrochemical potentials, a feature that facilitates analysis of mixed ion and electron conduction. The present work focuses on analyzing oxygen chemical potential gradients within the solid electrolyte and the porous composite electrodes, with an emphasis on gradients near interfaces between the PEN components. Two general modeling cases are compared: one neglecting electronic conduction within the solid electrolyte and one accounting for small yet present electronic conduction.  Electrochemical potential distributions are assessed across the cell structure over a range of electrolytic and galvanic operating conditions. These distributions are used to assess the likelihood of adverse oxygen chemical potential gradients within the cell. The effects of interconnect geometry for planar cells are also considered. It is found that variations in electrochemical potential arise within the PEN structure, a phenomenon that may drive mechanical failure. These gradients may increase the likelihood of electrolyzer failure for certain combinations of electrode and interconnect geometry. The use of device scale geometric design is discussed as a means of mitigating these gradients and reducing the likelihood of cell mechanical failure from adverse distributions of reactant chemical potentials.
Hydrostatic Stress - Temperature Diagrams for Electronic Charge Carriers in SrTiO3
Authors: Youssef Mostafa , Van Vliet Krystyn J. , Yildiz Bilge
Published: February 2020

The electronic conductivity and the redox activity of metal oxides depend on the extent of the wave function spread of the electronic charge carriers. Delocalized (free) electrons and holes lead to large electronic conductivity, whereas self-trapped (small polaron) electrons and holes provide active centers for charge transfer and redox reactions. It is possible to control the state of the electronic charge carriers in metal oxides, free vs. self-trapped, by utilizing mechanical stress and strain. Tensile stresses tend to favor trapping, and the critical tensile stress above which trapping occurs also depends strongly on temperature. Here we adopt SrTiO3 as a model system and computationally predict regimes of trapping or delocalization for electrons and holes as a function of hydrostatic stress and temperature. SrTiO3 is a representative of the perovskite family of metal oxides, and itself is a widely used crystal for electronic studies. Starting from density functional theory (DFT), we parametrized on-site Hubbard terms (+U) for Ti 3d states and O 2p states that adhere to the generalized Koopman’s theorem. This adherence qualifies DFT equipped with the selected U to accurately describe trapped electrons and holes. Using this DFT+U approach we found that in SrTiO3 at zero temperature and zero stress, trapped holes on oxygen ions are favored by 170 meV, whereas free electrons are favored by 110 meV.  Using the quasiharmonic approximation we extend these results to finite temperature and finite hydrostatic stress. In particular we calculate the Gibbs free energy of formation of electrons and holes in both trapped and free states. Based on these free energies, we build a stress-temperature diagram for the predominant electronic defect state. The analysis we present here for SrTiO3 is broadly applicable to other semiconducting metal oxides, and illustrates how strain (or stress) can serve as a modulator of electronic charge carriers.
(Invited) Growth & Redox Capacity of Coherently Strained Ceria Ultrathin Films
Authors: Chueh William C
Published: February 2020

Cerium oxide is one of the most studied mixed ionic and electronic conductors. In this talk, I will present a systematic study of the oxygen capacity of ultrathin ceria films under significant compressive and tensile strain, starting at a thickness of 1 nm. Coherently strained ceria thin films were grown on various single-crystalline substrate substrates via pulsed-laser deposition. Using in-situ electron diffraction and high-resolution transmission electron microscopy, the precise thickness at which the growth transitions between 2-D growth, 3-D island growth and plastic deformation through the creation of misfit dislocation is identified. The redox capacity of the ultrathin ceria films were characterized using ambient pressure X-ray photoelectron spectroscopy, which exhibits an ununsual dependece on misfit strain.
(Invited) Multi-Modality X-Ray Imaging at a 10 Nanometer Resolution
Authors: Chu Yong S , Yan Hanfei , Huang Xiaojing , Kalbfleisch Sebastian , Ge Mingyuan , Lauer Kenneth , Nazaretski Evgeny
Published: February 2020

The Hard X-ray Nanoprobe (HXN) beamline at the NSLS-II is constructed to explore new frontiers of the x-ray microscopy, by enabling an unprecedented spatial resolution of ~10 nm in the hard x-ray regime.  The beamline offers simultaneous multi-modality imaging capabilities including x-ray fluorescence, x-ray diffraction, x-ray absorption, x-ray scattering, phase-contrast imaging, spectroscopy, and ptychography.  These suite of imaging tools open up new scientific opportunities to visualize complex nanostructures with unprecedented sensitivity to material composition, morphology, crystalline phases/strain, and chemical state.  Use of hard x-rays allows accurate quantification of buried nanostructure with straightforward analyses.   Presentation will describe the present and near-future scientific capabilities of this new imaging facility with the recent results.
(Invited) Numerical Simulation of Sintering Process in Solid Oxide Fuel Cell Anode
Authors: Shikazono Naoki , Hara Shotaro
Published: February 2020

Solid oxide fuel cell (SOFC) is expected as a promising energy conversion device because of its high efficiency and fuel flexibility.  It is widely known that electrode microstructures are of great importance for attaining high performance as well as high reliability of SOFCs.  In the SOFC fabrication processes, sintering of sub-micron scale ceramic and metallic powders is one of the most important step to achieve efficient and reliable electrodes. In addition, microstructural changes in SOFC anodes associated with particle sintering during high temperature operation may lead to severe performance degradation. Thus, in order to develop more reliable electrodes of SOFC, a method that can offer quantitative information of sintering behavior at the sub-micron scale is highly demanded.

Accurate prediction of microstructure evolution during sintering, even in single-phase systems, is still very challenging. This is because sintering behavior is deeply affected by the three-dimensional (3D) complex geometries of the powder compacts, such as grain and pore size distributions, their shapes, relative density and coordination number, etc. Among many types of numerical approaches, a mesoscale kinetic Potts Monte Carlo (KMC) method has the potential to overcome this difficulty [1]. This method is capable of capturing three dimensional microstructural evolution from the initial to the final stages of solid-state sintering.  However, the underlying kinetics at the sub-micron scale are not yet completely understood. Validation of the results using quantitative 3D microstructure data is indispensable to develop a numerical simulation tool which can reproduce proper sintering trajectory of real powder sintering.

In the present study, KMC simulations of nickel (Ni) and nickel oxide - yttria stabilized zirconia (NiO-YSZ) composite are carried out starting from the green powder microstructure obtained using focused ion beam - scanning electron microscopy (FIB–SEM). Quantitative topological changes during sintering of real powder compacts are obtained by FIB–SEM. This technique offers a great advantage because of its high resolution, which is sufficient to capture the 3D geometric nature of sub-micron-sized powder compacts (typically < 1/10 of the powder size). The simulated temporal trajectories of microstructural parameters are compared with the experimental data from FIB-SEM to verify the numerical modeling results.

[1] Hara, S., Ohi, A. and Shikazono, N., Sintering Analysis of Sub-Micron-Sized Nickel Powders: Kinetic Monte Carlo Simulation Verified by FIB-SEM Reconstruction, J. Power Sources, 276, pp. 105-112 (2015).
(Invited) The Stability of Solid Oxide Fuel Cells: Insights through in Situ X-Ray Tomography
Authors: Kennouche David , Chen-Wiegart Yu-chen Karen , Yakal-Kremski Kyle J , Wang Jun , Gibbs John , Barnett Scott A , Voorhees Peter W
Published: February 2020

With the advent of high energy x-ray sources it is now possible to follow microstructural evolution in three dimensions and as a function of time. The ability to observe and quantify the the evolution processes provides fundamentally new insights into factors controlling the microstructure of materials.  We illustrate this through observation of the high-temperature microstructural evolution of a solid oxide fuel cell Ni-Yttria-stabilized zirconia (Ni-YSZ) anode. Unlike prior studies that compared microstructural differences between different anodes, this three-dimensional measurement directly shows the changes occurring in the same region of an anode, enabling a new understanding of evolutionary processes. High-temperature ageing for 48 h at 1050 °C yielded substantial structural changes in the Ni, YSZ and pore networks, including coalescence of Ni particles, leading to a three-fold decrease in three-phase boundary length. The implications for long-term degradation of fuel cells will be discussed, as well as time resolved x-ray tomography.
(Invited) Single Step Direct Electrocatalytic Reduction of CO2 towards CO and Hydrocarbons
Authors: Schmid Guenter , Reller Christian , Krause Ralf Karl , Schmid Bernhard , Neubauer Sebastian Stefan , Fleischer Maximilian
Published: February 2020

Switching from fossil based to renewable power generation requires the installation of large overcapacities of wind and solar due to their intermittency. Storage or conversion possibilities are essential due the volatility of electricity. Economic feasibility is difficult when considering the low fossil energy carrier prices and the physical efficiency limitations of the processes.  Therefore, we choose to focus on high volume chemical feedstock such as Ethylene or CO, where the chemical value exceeds by far its pure heating value.

Electrocatalyts facilitate the conversion of CO2 to valuable base chemical feedstocks – for selectivity improvements substantial advances in electrode design are required. Depending on the electro catalytic system, CO2 can be electrochemically reduced to carbon monoxide (CO), methane (CH4), ethylene (C2H4) and various other hydrocarbons even in aqueous media. CO could be obtained with faradic efficiencies over 90% at current densities exceeding the industrial necessary level of 100 mA/cm² with a total energy efficiency approaching 50%. Ethylene is more challenging due the highly complex reduction process involving 12 electrons and 8 protons. Faradic efficiencies up to 57% for ethylene at current densities above 150 mA/cm² could be obtained using in-situ-deposited nano-structured copper based electrocatalysts. In many experiments we observed a large gap in the sum of the current efficiencies of gaseous products to 100% FE. It is well known, that the electro-reduction of CO2 also yields liquid products. This gap could be fully closed by detailed analysis of the electrolyte revealing a strongly pronounced formation of ethanol (> 20% FE) accompanied by wide range of C1-C3 alcohols, carboxylates and ketones in yields up to ~ 5%. To the best of our knowledge, the here reported faradaic efficiencies for ethanol above 20% in a current density regime above 150mA/cm2 have been unpresent in the literature so far.  In addition time resolved parallel analysis of the gaseous and liquid  product distribution revealed striking relationships between different species i.e. the parallel formation of ethylene and ethanol.

Figure 1
(Invited) In Operando Optical Studies of Solid Oxide Electrochemical Cells
Authors: Owrutsky Jeffrey C , Kirtley John D. , Qadri Syed Noorullah , Steinhurst Daniel A , Eichhorn Bryan W. , Walker Robert A
Published: February 2020

Solid oxide fuels cells (SOFCs) are promising devices for fuel flexible and efficient power generation. The high temperatures (>700 oC) required enable operation on hydrocarbon fuels but avoiding degradation by carbon deposition remains a challenge. In operando optical methods, including Raman and Fourier Transform infrared emission spectroscopy (FTIRES) and near infrared thermal imaging (NIRTI), have been developed to characterize and understand molecular and material processes in SOFCs in order to improve their performance and durability. Recent results include studies of SOFCs on methane operating under various reforming conditions. Dry reforming, using carbon dioxide, which is also simulated biogas, reveals a high degree of anode activity based on substantial cooling of the anode but also reduced carbon formation compared to unreformed methane.  An intermediate amount of anode cooling and carbon formation is observed with steam reforming. Related studies have been carried out to assess the effectiveness of carbon removal by steam and carbon dioxide using a new, duplex method in which NIRTI and FTIRES are performed simultaneously. Also, NIRTI has been used in conjunction with near ambient pressure X-ray photoelectron spectroscopy (APXPS) to identify spatially resolved regions where the emission intensity changes are observed due to ceria reduction during water electrolysis. The results are consistent with the APXPS results and interpretation for the reaction. The observations also provide an example of emissivity rather than temperature changes observed with high temperature thermal imaging in solid oxide electrochemical cells.
The Effect of Precusor Gel Desiccation, Ceria Oxide Pre-Infiltration, and Precursor Solution Additives on Infiltrated Lanthanum Strontium Ferrite-Lanthanum Strontium Cobaltite Solid Solution Nano-Particles
Authors: Burye Theodore E. , Tang Hongjie , Nicholas Jason D.
Published: February 2020

Abstract

Here, average La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) nano-particle sizes were controllably modulated from 48 to 24 nm by desiccating La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) precursor nitrate solutions or infiltrating La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) precursor nitrate solutions into Ce0.9Gd0.1O1.95 (GDC) scaffolds pre-infiltrated with a large amount of GDC nano-particles.  Scanning electron microscopy, thermo-gravimetric analysis, and x-ray diffraction experiments conducted on decomposed/decomposing precursor gels within, and outside of, porous GDC scaffolds showed that desiccation and pre-infiltrated nano-GDC resulted in reduced nitrate decomposition temperatures and reduced La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) average particle sizes.  GDC scaffolds infiltrated with La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) precursor gels, desiccated with CaCl2, and subsequently fired at 700oC, contained high-phase purity La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) nano-particles with average particle sizes ranging from 31-27 nm.  GDC scaffolds pre-infiltrated with nano-GDC infiltrated particles, infiltrated with La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) precursor gels and subsequently fired at 700oC, contained high-phase purity La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) nano-particles with average particle sizes ranging from 29-24 nm.  In contrast to comparable, standard nano-composite cathodes (NCC’s) containing 48 nm average-sized La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) particles and achieving polarization resistances of 0.10 Ωcm2 at 640°C, the best CaCl2-dessicated NCC’s achieved 0.10 Ωcm2 at 600°C, while the best pre-infiltrated nano-GDC NCC’s achieved 0.10 Ωcm2 at 540°C.

Acknowledgements

This work was supported by National Science Foundation award number CBET-1254453.

 

Figure 1.

Scanning electron micrographs for La0.6Sr0.4CoxFe1-xO3-δ nano-particles produced inside a GDC scaffold at 700°C for citric acid-containing precursor gels that were standard (a-e) desiccated (f-j) and pre-infiltrated nano-GDC oxide particles (k-o). Note, LSF = La0.6Sr0.4FeO3-x, LSFC = La0.6Sr0.4Fe0.8Co0.2O3-x, LSCF55 = La0.6Sr0.4Fe0.5Co0.5O3-x, LSCF = La0.6Sr0.4Co0.8Fe0.2O3-x, and LSC = La0.6Sr0.4CoO3-x. All scale bars are 50 nm in width.

Figure 1
Fuel Cell Performance of (Cyanamide + Polyaniline)-Iron-Carbon Cathode Catalyst
Authors: Chung Hoon T , Yin Xi , Purdy Geraldine M , Martinez Ulises , Cullen David A. , Mukundan Rangachary , More Karren L. , Zelenay Piotr
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are a green alternative to the internal combustion engine, particularly in the transportation sector. Currently platinum (Pt) is a state-of-the-art catalyst for both anode and cathode. As the oxygen reduction reaction (ORR) is inherently six orders of magnitude slower than the anodic hydrogen oxidation, there is a significantly higher Pt loading requirement for the cathode. Volatile pricing and geopolitical instabilities of the precious-metal market have thus enthused the development of entirely non-platinum group metal (non-PGM) cathode catalysts for PEFCs.

With the recently realized highly active non-PGM catalyst development,1-5 implementing these catalysts into PEFCs and demonstrating high fuel cell performance (i.e., competitive with state-of-the-art Pt catalysts) is becoming increasingly needed. Up until now, a majority of non-PGM catalysts have been tested under H2-O2 conditions, which tend to mask the true effects of mass transport likely encountered under practical automotive applications conditions (H2-air).

Recently, we introduced a new non-PGM ORR catalysts derived from two nitrogen precursors, cyanamide and polyaniline, both exhibiting high H2-air fuel cell performances.6 To understand the fuel cell performance of these catalysts more deeply under H2-air condition, we have tested/characterized theses catalysts using diverse H2-air fuel cell test conditions and characterization methods: H2-helox fuel cell testing, impedance characterization, as well as carbon dioxide and fluoride emissions detection. These results promise to provide a better insight into the performance of the dual nitrogen precursor catalysts under the conditions approaching those of an automotive fuel cell power system.

Acknowledgement

Financial support for this research by DOE-EERE through Fuel Cell Technologies Office is gratefully acknowledged. Microscopy research supported through a user project at ORNL’s Center for Nanomaterials Sciences, which is an Office of Science User Facility.

References

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H. Chung, D. Higgins, D-H. Kim, G. Wu, U. Tylus, K. L. More, D. Cullen, P. Zelenay, 227th ECS Meeting, Chicago, IL, USA (2015).
Ternary Transition Metal Oxide Nanoparticles with Spinel Structure As Oxygen Reduction Reaction Electrocatalysts
Authors: Toh Rou Jun , Eng Alex Yong Sheng , Sofer Zdenek , Sedmidubsky David , Pumera Martin
Published: February 2020

Electrocatalysts for the oxygen reduction reaction (ORR) has been developed to meet the requirements for renewable energy applications. Herein, we explore mixed valence transition-metal oxides with a spinel structure for this purpose. A simple and scalable method was employed for synthesis of four different types of spinel oxide nanocrystals (NiCo2O4, NiMn2O4, ZnCo2O4, and ZnMn2O4). This allowed for a systematic investigation of the influence of the composition of the catalysts (XY2O4, X=Ni, Zn and Y=Co, Mn) on ORR. Given the general spinel structure of XY2O4, we changed X (Ni, Zn) and Y (Co, Mo) systematically. The influence of different transition-metals on the morphology and electrocatalytic properties of the spinel oxides toward ORR were studied and compared using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron microscopy, and voltammetry. In general, cobalt-based spinel oxides exhibited significant electrocatalytic activity towards the ORR, with Ni-substituted spinel oxides outperforming their respective Zn-substituted congeners. These findings may have profound impact in the research field of renewable energy.
Electrochemical Deposition of PGM Based Fuel Cell Electro Catalysts
Authors: Mathe Mkhulu K. , Modibedi Remegia Mmalewane , Khotseng Lindiwe Eudora , Nonjola Patrick thabo , Ozoemena Kenneth I.
Published: February 2020

The talk will focus on the applications of electrochemistry and nanotechnology for the synthesis and characterisation of electro-catalysts used in fuel cells. Electrochemical methods such as, Electrochemical Atomic Layer Epitaxy (EC-ALE) and Electrochemical Atomic Layer Deposition (EC-ALD) are being explored for synthesis as other potential techniques used in the improvement of PGM based electro-catalysts for proton electrolyte membrane fuel cells (PEMFCs). Synthesis and characterisation of these electro-catalysts (nanostructured/ nanomaterials), including their proposed application in fuel cells, will be discussed as part of the talk. The connection of the electro-catalysis work to alkaline direct alcohol fuel cells (DAFCs) with focus on micro fuel cells and anionic membrane development will also be highlighted.

ACKNOWLEDGEMENT

The author wish to acknowledge the DST, NRF and CSIR for funding.

  References 1. F. Barbir, PEM Fuel Cells: Theory and Practice, Elsevier Academic Press, 2005, Oxford: p. 1-16. 2. T.S. Mkwizu, M.K. Mathe, I. Cukrowski, Langmuir. 26 (2009) 570-580 3. G. C. Abuin, E. A. Franceschini, P. Nonjola, M. K. Mathe, M. Modibedi, H. R. Corti, 279 (2015) 450-459.
Charge Transport through Organic Molecular Wires Embedded in Ultrathin Insulating Inorganic Membrane
Authors: Edri Eran , Frei Heinz
Published: February 2020

A hybrid organic-inorganic membrane for facilitating artificial photosynthesis is made by embedding surface bound molecular wires in an inorganic ~2 nm thick silica layer by low temperature atomic layer deposition. This membrane is meant to facilitate electron and proton transport between water oxidation and carbon dioxide reaction sites while blocking products and intermediate reactions by compartmentalizing the reaction microenvironments. Here the membrane is studied in a flat form as an intermediate step towards a working artificial photosynthesis system. The membrane is characterized using FT-IR, XPS and EDS-STEM, confirming the wires are intact and embedded in silica. Charge transport through the wires is confirmed by directly measuring the short circuit photocurrent generated by hole injection from a Ru based dye solution while at the same time blocking charge transport from Sn based dye solution which does not have the proper energy level alignment to inject charges to the wires. The incorporation of a molecular wire in an inorganic matrix may facilitate the incorporation of other molecular electronic building block and enable their use in other applications and fields of study.
Comparison of TiO2 and SnO2 Electron Transport Layers in Planar Perovskite Solar Cells
Authors: McCarthy Melissa , Walsh Adrian , Ryan Louise , Kegel Jan , Pemble Martyn E , O'Brien S , Povey Ian M
Published: February 2020

Over the past few years single junction perovskite solar cells have been extensively studied with reported power conversion efficiencies approaching 20% [1-3]. Despite such advances, high efficiency combined with low fabrication cost, parasitic absorptions and long term stability have remained issues. One approach to curtail some of these obstacles has been the investigation of planar architectures where the mesoporous TiO2/Al2O3 is removed from the cell and the electron transport layer (ETL) is reduced to a nanometre scale compact charge blocking layer [4]. Typically this layer has been TiO2 but more recently band gap engineering studies have shown that SnO2 has significant potential in removing TiO2 hysteresis effects whilst maintaining efficiencies [5]

In this study we examined planar stacks comprising glass/FTO/ETL/perovskite/spiro MeOTAD hole transport layer/contacts with an aim to further optimize the metal oxide ETL. The metal oxides studied in this work were atomic layer deposition grown SnO2, nominally undoped TiO2 and doped TiO2, all grown at temperatures below 180°C to align with the requirements of silicon-perovskite heterojunction cells [6]. The influence of the ALD growth parameters and composition of the ETL on the subsequent perovskite deposition, as well as the resultant cell performance are highlighted and discussed in terms of efficiency and hysteresis.

W.S. Yang et al.,
Science, 348, 1234-1237 (2015).

N.J. Jeon et al.,
Nature, 517, 476- 480, (2015).

S.D. Stranks et al., Science
342, 341-344, (2013)

M. Liu et al., Nature, 501, 395- 398, (2013).

J.P. Correa Baena, Energy and Environment Science, DOI:10.1039/c5ee02608c, (2015).

J.P. Mailoa et al., Applied Physics Letters, 106, 121105 (2015).
Investigations of the Electrochemical Behavior of Hydrocarbons in Adiponitrile
Authors: Cheek Graham T.
Published: February 2020

Introduction

       Recent investigations from this laboratory have shown that adiponitrile  (NCCH2CH2CH2CH2CN) / tetraethylammonium tetrafluoroborate  (TEABF4)  is  a versatile solvent system  for organic electrochemistry (1,2).   The  extraordinarily wide  eight volt potential window noted in earlier work (3) has been confirmed and applied to the measurement of water (1) and electrodeposition of metals (4).  The positive limit at +5 V vs Ag/AgCl opens up another 2 V for study, compared to that of most other solvents.  The present paper addresses the usefulness of the positive potential region for oxidation of hydrocarbons.

Experimental

       Adiponitrile was obtained from Sigma-Aldrich, and tetraethylammonium tetrafluoroborate was purchased from Southwestern Analytical Chemicals. Cyclic voltammograms were obtained on a PAR 283 potentiostat using PowerSuite software.  Potentials are referenced against a Ag/AgCl reference electrode (1).

Results and Discussion

       A cyclic voltammogram of 15 mM naphthalene in adiponitrile / 0.2 M TEABF4  is shown in the attached figure.  The reversible reduction of naphthalene is observed at -2.5 V, followed by an irreversible oxidation process at +1.74 V. Scan reversal at +2.00 V shows no reduction current associated with the oxidation process at 100 mV/s. If the potential scan is continued to +5.0 V,  considerable filming is observed, and the peak currents for the redox processes at -2.5 V are considerably lessened.  Similar behavior for naphthalene oxidation has been observed in acetonitrile (5), and the irreversible nature of the oxidation was ascribed to rapid coupling of naphthalene radical cations. These results show that the entire positive potential range in adiponitrile is available for study of the representative aromatic hydrocarbon naphthalene. 

References

G.T. Cheek,  ECS Trans., 58(46),  45-51 (2014).

G.T. Cheek,  ECS Trans., 61(30),  19-24 (2014).

H. Duncan, N. Salem, and Y. Abu-Lebdeh, J. Electrochem. Soc., 160 (6) A838-A848 (2013).

G.T. Cheek,  ECS Trans., 61(24),    9-14 (2014).

M.N. Cortona, N. Vettorazzi,  J. J. Silber, and L. Sereno, J. Electroanal. Chem., 394, 245-251 (1995).

Figure 1
Electroreductive Free Radical Coupling from Xanthates Derived from Acetophenones, New Route to 1,4-Dicarbonyl Compounds
Authors: Frontana-Uribe Bernardo A. , Lopez-Lopez Ernesto Emmanuel , Miranda-Gutierrez Luis Demetrio
Published: February 2020

In this contribution it is shown the synthesis of 1,4 dicarbonyl compounds from the electrochemical reduction of xanthates via a free radical coupling reaction. These starting materials are cheap and accessible. Electrosynthesis reaction is carried out in green chemistry conditions with excellent yields, which let to propose the route to be used as building blocks of more complex molecules or materials.

Acknowledgements: Funding by DGAPA UNAM project IN202011 is recognized

Figure 1
Electrochemical Generation of Stabilized Halogen Cation Pools
Authors: Yoshida Jun-ichi , Horiuchi Shun , Hayashi Ryutaro , Ashikari Yosuke , Shimizu Akihiro
Published: February 2020

Halogen cations such as I+ and Br+ are highly unstable species, although some of them are identified in the gas phase. The electrochemical oxidation provides a powerful method for generating and accumulating highly reactive cationic species in the solution, whereas the chemical methods are not effective because of reversibility of cation generation. We have already reported that some carbocations and onium ions can be generated and accumulated as cation pools at low temperatures (the “cation pool” method). However, halogen cations are very difficult to accumulate in the solution as “cation pools” because they are too unstable.

We envisioned that the use of a stabilizing agent that coordinates the cation being generated would solve the problem. Coordination of a neutral molecule gives a positively charged species and coordination of an anionic species gives a neutral species, although the halogen is the +1 oxidation state in both cases. Some stabilizing agents have already been reported. For example, Miller and co-workers reported the generation and accumulation of “I+” cation in acetonitrile (CH3CN), and later we reported the detection of CH3CN−I+ and (CH3CN)2I+ by cold-spray-ionization mass spectroscopy. Shono and co-workers reported that “I+” could be accumulated in trimethyl orthoformate (TMOF).

In this paper we report that dimethyl sulfoxide (DMSO) serves as a neutral stabilizing agent and that TfO− anion serves as a negatively charged stabilizing agent in the electrochemical generation and accumulation of halogen cations such as I+ and Br+.  We also report their reactions with organic molecules to give the corresponding halogen-containing products, which serve as useful transformations in organic synthesis.
Voltammetric Study and Electrodeposition of Zinc from Room Temperature Ionic Liquid 1-Butyl-1-Methylpyrrolidinium Bis((trifluoromethyl)Sulfonyl)Imide
Authors: Chen Po-Yu , Wang Yu-Sheng
Published: February 2020

Voltammetric behavior of Zn(II) introduced into the room temperature ionic liquid 1-butyl-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide (RTIL BMP-TFSI) via the addition of ZnCl2 or Zn(TFSI)2 salt was studied. It is surprised that ZnCl2 is highly soluble in this IL because many transition metal chlorides are insoluble in the TFSI-based ILs, leading to the retardation of applying the RTIL BMP-TFSI to electrodeposition. Two redox couples both associated to the redox reaction Zn(II) + 2e− ↔ Zn were observed in the ZnCl2 solution, which resulted from the nonchloride-coordinated and chloride-coordinated Zn(II) species, respectively. However, a single redox couple corresponding to Zn(II) + 2e− ↔ Zn was observed in the Zn(TFSI)2 solution (Figure 1). According to the experiments of voltammetric titration, it was supposed that TFSI anions exhibit much stronger coordinating ability towards Zn2+ ions than to other common transition metal ions, resulting in the high solubility of ZnCl2 in BMP-TFSI. A sufficient amount of chloride anion must be introduced in order to observe the chloride-coordinated Zn(II) species in the Zn(TFSI)2 solution. Afterwards, TFSI anions coordinated to Zn2+ ions were gradually replaced by chloride ions continuously introduced into the Zn(TFSI)2 solution. Finally, no zinc redox couple could be observed once Zn2+ions were completely coordinated with chloride ions.

    Electrodeposition of Zn was achieved by potentiostatic electrolysis using copper substrates as the electrodes from the IL containing ZnCl2 and Zn(TFSI)2, respectively. Crystalline Zn could be obtained from the two different solutions. The crystallinity and surface morphology of the Zn electrodeposits depended on the applied potentials, and nanostructured Zn could be obtained at some particular electrodepositing potentials. An interesting current-vibration behavior was observed during the potentiostatic electrodeposition of Zn from ZnCl2 solution, and this vibration behavior obviously depended on the applied potentials. It was supposed that the current-vibration behavior was due to a chloride-releasing & chloride-combination mechanism accompanied with the diffusion-drove supplementary of electroactive Zn(II) species because the vibration phenomenon was only observed while the applied potentials were set at where the chloride-coordinated Zn(II) species was reduced in the ZnCl2 solution.

Figure 1