bluuebunny/crossref_metadata_2025 huggingface dataset:
Flowing Electrolyte Metal Batteries
Authors: Parekh Mihir , Rahn Christopher D
Published: July 2021

Flowing electrolyte metal batteries (FEMBs) are a new class of energy storage devices with metal anodes and flowing electrolytes. In this presentation, electrochemical models predict that flowing electrolyte can accelerate diffusion-limited transport, reducing impedance, increasing stability, and improving coulombic efficiency and cycle life. Electrolyte flow toward the metal electrode reduces and, for flow velocities above a critical speed, changes the sign of the electrolyte impedance, allowing faster charging without exceeding voltage limits. The critical flow rate is very slow (~μm/s) and directly proportional to the charging current density. Concentration of diffusion flux at dendrite tips is responsible for accelerated dendrite growth in metal batteries, so introduction of creeping electrolyte flow normal to electrodes levels ion concentration and eliminates dendrites above the critical speed. Creeping normal flow also significantly reduces solid electrolyte interphase (SEI) growth rate [1]. Creeping Poiseuille and Couette flows that are parallel to the electrodes have no impact on impedance or SEI layer growth, but do reduce dendrite growth, albeit much less effectively than normal flow [2]. Both creeping normal and parallel flows eliminate/reduce dendrite growth, so introducing electrolyte flow, in general, is a promising method to control dendrite growth. As dead Li formation is tied to dendrite growth, and as creeping normal flow eliminates dendrites and reduces SEI layer growth [3], creeping normal flows significantly improve coulombic efficiencies, and cycle life. The low flow rates indicate potential for practical applications.

[1] Parekh, Mihir N., Christopher D. Rahn, and Lynden A. Archer. "Controlling dendrite growth in lithium metal batteries through forced advection." Journal of Power Sources 452 (2020): 227760.

[2] Parekh, Mihir N., and Christopher D. Rahn. "Reducing Dendrite Growth in Lithium Metal Batteries by Creeping Poiseuille and Couette Flows." Journal of the Electrochemical Society (2020).

[3] Parekh, Mihir N., and Christopher D. Rahn. “Solid electrolyte interphase growth on lithium metal electrodes with normal electrolyte flow.’’ Journal of the Electrochemical Society (Submitted).

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(Invited) Development of Blue Vertical Cavity Surface Emitting Lasers (VCSELs) with Nanoporous GaN
Authors: Han Jung , Elafandy Rami , Kang Jin-ho
Published: July 2021

Blue and green vertical cavity surface emitting lasers (VCSELs) are expected to be used in future generation display and lighting applications. Applications in virtual reality (VR), augmented reality (AR), retinal scanning display (RSD), and portable projection devices are only a few of the anticipated applications. However, in spite of vigorous pursuit for more than two decades, GaN VCSELs have yet reached commercialization.

The main challenge in the technology of III-nitride VCSELs is the fabrication of distributed Bragg reflectors (DBRs) that can provide near-unity reflection and thus support the formation of high-quality vertical cavity. Several groups reported VCSEL operations using epitaxial DBRs (using AlGaN/GaN or AlInN/GaN) and dielectric DBRs (involving lift-offs or epitaxial lateral overgrowth). In this talk, we will discuss an alternative approach to this challenging problem by using electrochemistry to create nanoporous GaN as a low-index medium, toward a manufacturable DBR mirror technology to support blue and green VCSELs. This nano-engineering based on electrochemistry can help to circumvent impasses and creates new dimensions in the exploration of optoelectronic devices using GaN.

We acknowledge research support from US Department of Energy, National Science Foundation, DARPA, and IP Group.
(Invited) A Chiral Switchable Photovoltaic Ferroelectric Semiconductor
Authors: Shi Jian
Published: July 2021

Symmetry is an essential knob in designing and engineering physical properties of materials. In this talk, I will discuss our efforts on searching ferroelectric semiconductors that lack mirror symmetry. I will present the discovery of a previously unknown low-dimensional hybrid perovskite material with electric field-switchable pyroelectricity and optical chirality. This discovery will facilitate the exploration of phenomena such as electric field and chiral enantiomer–dependent Rashba-Dresselhaus splitting and circular photogalvanic effects.
Hydrogen Incorporation Modulates Subgap Density of States in Amorphous InGaZnO Thin-Film Transistors
Authors: Mattson George , Vogt Kyle , Wager John , Graham Matt
Published: July 2021

Incorporation of hydrogen into the channel layer of an amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor leads to a negative shift in the transfer curve threshold voltage; the magnitude of the threshold voltage shift increases with increasing hydrogen content. Although several atomic models for hydrogen incorporation into a-IGZO have been proposed, hydrogen-induced changes in the sub-gap density of states have never before been directly measured. By employing ultrabroadband photoconduction (UBPC),1,2 we directly observe a large increase in the near-valence band UBPC response in hydrogen-enriched devices; the increase in UBPC response scales with hydrogen concentration.3 This UBPC trend is consistent with the formation of OH states resulting from the interaction of incorporated hydrogen with oxygen already present in the a-IGZO channel layer and explains the observed negative threshold voltage shift in the device transfer curve.

K. T. Vogt, C. Malmberg, J. Buchanan, G. Mattson, M. Brandt, D. Fast, P. H.-Y. Cheong, J. F. Wager, M. W. Graham, (2020) Ultrabroadband Density of States of Amorphous In-Ga-Zn-O, Phys Rev Res, 2, 033358

K. T. Vogt, G. W. Mattson, J. F. Wager, M. W. Graham (2020) Ultrabroadband Photoconduction Response of Sub-gap Defects in Amorphous In-Ga-Zn-O Thin Film Transistors, ECS Transactions, 97 (7), 339-357

G. W. Mattson, K.T. Vogt, C. Malmberg, P. H.-Y. Cheong, J. F. Wager, M. W. Graham, (2020) Effect of hydrogen incorporation on sub-gap density of states in amorphous InGaZnO thin-film transistors, Proc. SPIE, Oxide-based Materials and Devices XI, 112811G, doi.org/10.1117/12.2545439

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Investigation of Electrical and Optical Properties of Low Resistivity Indium Oxide Thin Films
Authors: Sundaresh Sreeram , Nehate Shraddha Dhanraj , Sundaram Kalpathy B.
Published: July 2021

Indium Oxide (In2O3) is a wide bandgap (~3.6eV) n-type transparent conducting oxide (TCO) semiconductor with high conductivity and good transparency in the visible region [1]. In2O3 finds several applications such as photovoltaic devices, transparent windows in liquid crystal displays and heterojunction solar cells [2]. The electrical and optical properties of In2O3 films vary depending on the partial pressure of the reactive gas used for the specific deposition technique, target to substrate distance, temperature at which the substrate is exposed during heat treatment following deposition, and the ambience in which it is treated [3]. In2O3 films has been deposited using vacuum evaporation, sputtering [4], chemical vapor deposition [5], spray pyrolysis [6], ion assisted deposition [7], spin coating [8] and atomic layer epitaxial growth [9].

In this work, In2O3 films are deposited on glass substrates by reactive sputtering of In2O3 target in presence of oxygen gas. The deposition was carried out under different flow rates of oxygen. The influence of oxygen gas flow on electrical and optical characteristics of the films are studied. Influence of oxygen gas flow on electrical resistivity of In2O3 thin films is investigated. Transmission characteristics of the deposited films are studied using UV-visible spectrophotometer. Absorption coefficient is calculated from the transmission values and optical bandgap is extracted from Tauc-plot.

Min-Suk Lee, Won Chel Choi, Eun Kyu Kim, Chun Keun Kim, Suk-Ki Min, Characterization of the oxidized indium thin films with thermal oxidation, Thin Solid Films, Volume 279, Issues 1–2, 1996, Pages 1-3, ISSN 0040-6090.

Abbas bagheri khatibani, Seyed Mohammad Rozati, Z. Bargbidi (2012). Preparation, Study and Nanoscale Growth of Indium Oxide Thin Films. Acta Physica Polonica Series a. 122. 220. 10.12693/APhysPolA.122.220.

Radhouane Bel Hadj Tahar, Takayuki Ban, Yutaka Ohya, and Yasutaka Takahashi, Tin doped indium oxide thin films: Electrical properties, Journal of Applied Physics 83:5, 2631-2645.

Sundaram, K.B. and Bhagavat, G.K. (1981), Preparation and properties of indium oxide films. phys. stat. sol. (a), 63: K15-K18.

Cheng, G., Stern, E., Guthrie, S. et al. Indium oxide nanostructures. Appl. Phys. A 85, 233–240 (2006).

Memarian, N., Rozati, S.M., Elamurugu, E. and Fortunato, E. (2010), Characterization of SnO2:F thin films deposited by an economic spray pyrolysis technique. Phys. Status Solidi (c), 7: 2277-2281.

S. Cho, K. H. Yoon, S. K. Koh, J. Appl. Phys. 89, 3223 (2001).

Gurto, M. Ivanovskaya, A. Pfau, U. Weimer, W. Gopel, Thin Solid Films 307, 288 (1997)

Aikainen, M. Ritala, W. M. Li, R. Lappalainen, M. Leskele, Appl. Surf. Sci. 112, 231 (1997).
(Invited) Defects in Cast-Mono Crystalline Silicon
Authors: Yang Deren
Published: July 2021

Crystalline silicon, including Czochralski silicon (Cz-Si) and multicrystalline silicon (mc-Si),is main material for photovoltaic (PV) industry. How to produce more productive and less expensive crystalline silicon materials is still a big challenge. As we know, the seed-assisted growth method can be used to fabricate cast-mono (CM-Si) silicon by directional solidification, which should combine the both advantages of Cz-Si and mc-Si. However, there remain some problems to be resolved in growing CM-Si silicon ingots, particularly the control of dislocations which are the major and most detrimental defects in CM-Si. They can act as precipitation sites for impurities and thus reduce the carrier lifetime in ingots. Unlike mc-Si ingots, once dislocations are generated in the bottom of CM-Si ingots, they will glide and propagate along the growth direction without hindrance due to the lack of grain boundaries.

In this presentation, we review our recent work of how to control defects, specially dislocations, in CM-Si. We induce a grain boundary by adjusting the orientation of seeds which can suppress the generation of dislocations originated from the junction of seeds. We have investigated the effect of Σ5, Σ13a grain boundary relationship at seed junctions of <100>-oriented CM-Si on dislocations and solar cell performance. We also use <110>-oriented seeds to grow new orientation CM-Si ingots to control the generation and propagation of dislocations. The results show that by designing the orientation of seeds, the dislocation density can be decreased and the solar cell efficiency can be improved obviously.
(Invited) Applications of the Hakoniwa Method to Impurity Atoms Wandering Inside Si Wafers
Authors: Kamiyama Eiji , Sueoka Koji
Published: July 2021

In this presentation, we review applications for Si-related materials by utilizing the Hakoniwa method, an approach that predicts material properties on the basis of statistical thermodynamics and ab initio calculations. This method describes the behavior of Cu/Fe atoms in B-doped Si crystals. The target material (inside Si wafers) is not uniform and therefore needed to be described in a local circumstance around wandering impurity atoms inside the wafers in order to estimate compatible values with the experiments. Further descriptions are also discussed to estimate Cu/O solubility. These all approaches are spatial-averaged from the viewpoint of statistical thermodynamic treatments. Expanding the Hakoniwa method to a time-averaged approach for the SiO2/Si interface can provide a novel description of oxidizing reactions in the SiO2/Si interface and enable estimation of the interface state density.
(Invited) Interface Treatment Related Defects During Ge Gate Stack Formation
Authors: Misra Durga
Published: July 2021

Germanium as a high mobility channel material is currently of considerable interest since Ge has both higher electron and hole mobility as compared to silicon (1). The deposition of high-k dielectrics on Ge has been a significant challenge because of high interface defects density, Dit
(2). By considering the interface reaction kinetics, thermal budget various atomic layer deposition (ALD) schemes and interface treatments can be identified to get a stable dielectric with a robust interface. However, understanding of the interface kinetics and defect distribution into gate stack and/or Ge is still limited.

In this work, we report the impact of different interface treatments on the p type Ge prior to any high-k layer deposition on defect generation. Ge surface was oxidized by a controlled chemical oxidation, slot-plane-antenna plasma oxidation and oxidation through vapor O3 treatment before ALD deposition of 1nm Al2O3/3.5nm ZrO2 for gate stack formation. These devices were characterized to evaluate the interface and possible bulk defects by deep level transient spectroscopy (DLTS), capacitance spectroscopy, conductance method in addition to standard I-V and C-V measurements. DLTS has the advantage to have the spectrum comparison among the interface treatments. Signature of these spectra can reveal the difference, which is more accurate than the defects estimated by Conductance method. DLTS also provides the signature of slow traps (~1ms) (Fig. 1) originating from the bulk or interface depending on the type of GeOx formation.

Furthermore, we evaluate the defect distribution when the gate stack was subjected to a slot-plane antenna plasma oxidation prior to metal deposition. A TiN/Hf1-xZrxO2/Al2O3/Ge gate stack with six different Zr content was investigated (Fig. 2). Al2O3 was used to impede the Ge diffusion into the gate stack. Interface state density (Dit) and C-V hysteresis show that the mid-gap Dit tend to increase with decrease in EOT, possibly due to the undesirable native oxide formation on Ge.

The author would like to thank Drs. Y.M. Ding (Western Digital Corporation, Shanghai, China), M.N. Bhuyian (Globalfoundries, Malta, NY, USA), K.L. Ganapathi (Indian Institute of Technology Madras, India), N. Bhat, (Indian Institute of Science, Bangalore, India) and K. Tapily, R. D. Clark, S. Consiglio, C. S. Wajda, G. Nakamura, and G. J. Leusink of TEL Technology Center, America, Albany, NY, for their help in this work.

References

Arimura et al, IEDM Technical Digest, (2020)

N. Bhuyian et al, ECS Journal of Solid-St. Sci. and Tech., vol. 7(2), N1-N6, (2018)

G. Kolla et al, J. Vac. Sci. Technol. B, 36(2), 021201 (2018)

Ding et al, IEEE Trans. on Dev. and Materials Reliability, 17(2), 349-354, (2017)

Ding, et al, J. of Vac. Sci. and Technol. B, 34(2), 021203, 2016.

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Microscale Optoelectronic Devices for Biomedical Sensing
Authors: Sheng Xing
Published: July 2021

Conventional bioelectrical sensors and systems integrate multiple power harvesting, signal amplification and data transmission components for wireless biological signal detection. Here we report that the real-time biophysical and biochemical activities can be optically captured using a microscale light-emitting diode (micro-LED), eliminating the need for complicated sensing circuit. Such a thin-film diode based device simultaneously absorbs and emits photons, enabling wireless power harvesting and signal transmission. Additionally, owing to its strong photon-recycling effects, the micro-LED’s photoluminescence (PL) emission exhibits a superlinear dependence on the external conductance. Taking advantage of these unique mechanisms, instantaneous biophysical signals including galvanic skin response, pressure and temperature, and biochemical signals like ascorbic acid concentration, can be optically monitored, and it demonstrates that such an optoelectronic sensing technique outperforms a traditional tethered, electrically based sensing circuit, in terms of its footprint, accuracy and sensitivity. This presented optoelectronic sensing approach could establish promising routes to advanced biological sensors.
(Invited) Bioelectronic Modulation with Soft-Hard Composites
Authors: Tian Bozhi , Prominski Aleksander
Published: July 2021

Biointerface devices can probe fundamental biological dynamics and improve the lives of human beings. However, the direct application of traditional rigid electronics onto soft tissues or cells can cause signal transduction and biocompatibility issues, due to mechanical mismatch at the biointerfaces. One common mitigation strategy is the use of nanostructures or soft-hard composites to form more biocompatible interfaces with target cells or tissues. My group integrates nanoscience and soft matter physics with biophysics to study several semiconductor- or conductor-based biointerfaces. In this talk, I will first pinpoint domains where semiconductor properties can be leveraged for biointerface studies. Next, I will present a few recent studies from our lab and highlight key bioelectrical mechanisms underlying the non-genetic optical or electrochemical modulation interfaces. The non-genetic and soft-hard composite-based methods have the potential to overcome the limitations of current metal electrode-based devices such as bulk and cell membrane disruption, and are not dependent on genetic modifications. Finally, I will discuss new tissue-like materials and other biological targets that could catalyze future advances.
(Invited) Flexible, Stretchable and Healable Electronics
Authors: Cicoira Fabio
Published: July 2021

Organic electronics, based on semiconducting and conducting polymers, have been extensively investigated in the past decades and have found commercial applications in lighting panels, smartphone and TV screens using OLEDs (organic light emitting diodes) technology. Many other applications are foreseen to reach the commercial maturity in future in areas such as transistors, sensors and photovoltaics.

Organic electronic devices, apart from consumer applications, are paving the path for key applications at the interface between electronics and biology, such as in polymer electrodes for recording and stimulating neural activity in neurological diseases. In such applications, organic polymers are very attractive candidates due to their distinct property of mixed conduction: the ability to transport both electron/holes and ionic species. Additionally, conducting polymers offer the possibility to tune their surface properties (e.g., wettability or chemical reactivity) by changing their oxidation state, thus promoting or hindering the adhesion of biomolecules. This feature can be particularly useful for enhancing the biocompatibility of implantable electrodes.

My talk will deal with processing and characterization of conducting polymer films and devices for flexible, stretchable and healable electronics.

Self-healing electronic materials are highly relevant for application in biology and sustainable electronics. We observed mechanical and electrical healability of PEDOT:PSS thin films. Upon reaching a certain thickness (about 1 µm), PEDOT:PSS thin films damaged with a sharp blade can be healed by simply wetting the damaged area with water. The process is rapid, with a response time on the order of 150 ms. Significantly, by blending with other polymers, the films are transformed into autonomic self-healing materials without the need of external stimulation. This reveals a new property of PEDOT:PSS and enables its immediate use in flexible and biocompatible electronics, such as electronic skin and bio-implanted electronics, placing conducting polymers on the front line for healing applications in bioelectronics.

References

[1] S. Zhang, F. Cicoira, Water-Enabled Healing of Conducting Polymer Films, Adv. Mater. 29, 1703098, 2017.

[2] Y. Li, X. Li, S. Zhang, L. Liu, N. Hamad, S. R. Bobbara, D. Pasini, F. Cicoira, Autonomic self-healing of PEDOT:PSS achieved via polyethylene glycol addition, Adv. Funct. Mater. 30, 2002853, 2020.

[3] Y. Li, S. Zhang, N. Hamad, K. Kim, L. Liu, M. Lerond, F. Cicoira, Tailoring the Self-Healing Properties of Conducting Polymer Films, Macromol. Biosci. i2000146, 2020.
Flexible and Transparent Agnws-Based Microelectrode Arrays and Interconnects for Multifunctional Electrical and Optical Biointerfacing
Authors: Chen Zhiyuan , Boyajian Nicolas , Lin Zexu , Yin Rose T , Efimov Igor R , Lu Luyao
Published: July 2021

Transparent microelectrode provides a promising approach combining electrophysiology and optogenetics for multi-functional biointerfacing. Flexible platforms with high performance which can achieve seamlessly integrating with soft tissue systems are highly needed. Herein, we demonstrate silver nanowires (Ag NWs)-based transparent microelectrode arrays (MEAs) and interconnects to meet this demand by using an innovative photolithography-based solution-processing technique. The resulting microelectrodes exhibit a high transparency of 76.1-90.0% over the visible spectrum, and low normalized electrochemical impedance of 3.4-15 Ω cm2 at 1 kHz which is comparable to that of opaque solid Ag films (12.4 Ω cm2). 93% transparency at 550 nm can be achieved through patterning the nanowire networks. Additionally, the microelectrodes possess excellent sheet resistance of 11-25 Ω sq−1, superior mechanical stability for 100,000 bending cycles at 5 mm radius, and chemical stability after 30-day soaking at 37 oC. In vivo histology study reveals the biocompatibility of the device. Studies on rat and transgenic mouse hearts show the ability of Ag NWs MEAs to optical mapping with negligible light-induced artifacts and real-time monitoring of heart rhythm under simultaneously optogenetic pacing with high-fidelity, respectively. This work illustrates that the Ag NWs-based platform can serve as a promising candidate for the next-generation of large-scale multi-functional biointerfaces for biological and biomedical research.

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(Invited) Laser-Engraved Graphene-Based Wearable/mHealth Biosensors
Authors: Gao Wei
Published: July 2021

Wearable sensors have the potential to provide rapid, non-invasive, and in-home health monitoring by real-time analyzing biomarkers in human sweat and saliva. However, most current biosensors suffer from low sensing accuracy for low-level analyte detection in biofluids and are difficult to fabricate on a large scale. In this talk, I will review our latest advances in developing fully-integrated laser-engraved graphene-based biosensors which can selectively and accurately measure a wide spectrum of sweat and saliva biomarkers including metabolites, nutrients, hormones, and proteins. The clinical value of these telemedicine platforms is evaluated through multiple human studies involving both healthy and patient populations toward metabolic monitoring and stress assessment. I will also introduce our recent work on a multiplexed wireless platform for the rapid COVID-19 test which could provide information on infection status, severity, and immunity. We envision that these telemedicine devices could open the door to a wide range of personalized healthcare applications.
(Invited) Soft Microfluidic Systems for the Skin
Authors: Rogers John
Published: July 2021

Biological tissues are mechanically soft, with complex, time-dependent 3D curvilinear shapes; modern microfluidic technologies are rigid, with simple, static 2D layouts. Eliminating this profound mismatch in physical properties will create vast opportunities in man-made systems that can intimately integrate with the human body, for diagnostic, therapeutic or surgical function with important, unique capabilities in fitness/wellness, sports performance and clinical healthcare. Over the last decade, a convergence of new concepts in materials science, mechanical engineering, electrical engineering and advanced manufacturing has led to the emergence of diverse, novel classes of 'biocompatible' electronic and microfluidic systems with skin-like physical properties. This talk describes the key ideas and presents some of the most recent device examples, with a focus on microfluidic platforms that can capture, manipulate and perform biomarker analysis on microliter volumes of sweat, with applications in precise hydration management in sports and fitness, including commercial devices featured on celebrity sports figures with Gatorade.
(Invited) Exploring the Easy, Cost-Effective Fabrications of Multifunctional on-Skin Wearable Bioelectronic Devices
Authors: Yan Zheng
Published: July 2021

As compared to conventional, rigid, bulky physiological monitoring tools, emerging on-skin wearable bioelectronic devices are ultrathin, lightweight, and small footprint and can find wide applications in point-of-care diagnostics because of their easy deployment outside hospital settings. At present, on-skin wearables are usually fabricated by patterning conventional inorganic materials, novel organic materials, or emerging nanomaterials on flexible supporting substrates. Consequently, the state-of-the-art on-skin wearables often suffer from expensive precursor materials, costly fabrication facilities, complex fabrication processes, and limited functionalities and disposability. By using widely accessible pencils and papers as the fabrication tools, we have developed a rich variety of cost-effective, disposable on-skin bioelectronic devices, ranging from biophysical sensors (e.g., temperature sensors, electrophysiological sensors) and sweat biochemical sensors (pH sensors, uric acid sensors) to thermal stimulators, humidity energy harvesters, and transdermal drug delivery systems. The enabled devices can find wide applications in point-of-care diagnostics, particularly in low-resource environments owing to their low-cost resources, handy operation, time-saving fabrication, and abundant potential designs. In addition, with laser-assisted patterning of conductive and semiconductive materials on flexible substrates, the maskless, scalable fabrications of on-skin wearable bioelectronic devices can be achieved.
Phase Formation during Reduction-Oxidation of Ni-Substituted Sr(Ti,Fe)O3-δ Solid Oxide Fuel Electrodes
Authors: Schmauss Travis Anthony , Mogni Liliana , Barnett Scott A
Published: July 2021

High performance solid oxide fuel cell anodes have recently been achieved via the exsolution of bimetallic (Ni,Fe) particles from a parent Sr(Ti,Fe,Ni)O3-δ (STFN) matrix. However, a number of unknowns remain regarding the detailed nature of the exsolution process, the role of initial A-site deficiency, and the effect of the change in perovskite stoichiometry during exsolution. In this study, the dynamics of exsolution are explored via thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM), both during exsolution and redox cycling. The diffraction results show that the (Ni,Fe) phase starts Ni-rich during the initial exsolution, gradually shifting to more Fe-rich with time; this result indicates that Ni diffusion towards the surface is occurring faster than for Fe. The TGA results suggest that holding STFN under too-reducing conditions can lead to continued Fe exsolution instead of reaching a stable equilibrium. TEM images display regions where SrO formed after Fe-Ni exsolution, likely as a consequence of increased A-site excess in the perovskite. In-situ re-oxidation and subsequent re-incorporation of exsolved species into the parent oxide have been suggested as a means to “reset” exsolution electrodes after degradation by, e.g., particle coarsening. The present TGA results taken during redox cycling suggest that a shorter oxidation step results in faster exsolution, a hint that, in this case, the exsolved surface species do not have sufficient time to fully re-incorporate into the oxide. The effects of new phase formation, changes in exsolved particle composition, and redox cycling on electrochemical characteristics will also be reported.

Figure 1. Ex-situ X-ray diffraction scans from Sr(Ti,Fe,Ni)O3-δ after reduction in 30% H2 – 3% H2O – 67% Ar, showing peaks from the perovskite matrix along with a peak associated with exsolved (Ni,Fe) metal alloy; the latter shifts with increasing reduction time indicating that the alloy becomes increasingly Fe-rich.

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Research Advancement of Energy to Molecules and Materials (E2M2) at Idaho National Laboratory
Authors: Ding Dong , Wu Wei , Wang Lucun , Ding Hanping , Hua Bin , Li Meng
Published: July 2021

Integrated Energy System (IES) is a core initiative at Idaho National Laboratory where energy to molecules and materials (E2M2) pillar plays a critical role, due to the widely available distributed feedstock, energy input (renewable and/or nuclear energy associated electricity and excess heat) as well as the resulting industrial electrification. These factors offer new opportunities to those technologies with smaller scale, modularized/distributed, and driven by an integrated system of renewable and other energy sources that can show promise for increased productivity with decreased energy, capital, and operating costs. Intermediate temperature electrochemical processing through the solid oxide cells is a promising strategy because it can efficiently utilize electrons and heat while overcoming and/or mitigating the challenges of their lower and higher temperature counterparts, including 1) the use of precious metal; 2) sluggish kinetics; 3) fast degradation; 4) costly interconnect materials. Despite of these promising features, this technology still faces many challenges that include but not limited to immature process, relatively low catalyst activity, and unproven operation durability. At Idaho National Laboratory, we have made significant achievements on electrosynthesis of intermediates, fuels and chemicals using natural gas, steam, carbon dioxide and nitrogen through protonic ceramic membrane reactors. The research outcomes have the potential to establish a globally competitive U.S. industry for converting the Nation’s abundant supply of feedstock into conversion-ready intermediates and/or high demand fuels and chemicals.
Structure and properties of Cs7(H4PO4)(H2PO4)8: A new superprotonic solid acid featuring the unusual polycation (H4PO4)+
Authors: Wang Louis Shen , Patel Sawankumar , Sanghvi Sheel S. , Hu Yan-Yan , Haile Sossina
Published: July 2021

We report the discovery of a new superprotonic compound, Cs7(H4PO4)(H2PO4)8, or CPP, which forms at elevated temperatures from reaction of CsH2PO4 and CsH5(PO4)2. The structure, solved using high temperature single crystal x-ray diffraction and confirmed by high temperature 31P NMR spectroscopy, crystallizes in space group Pmn and has lattice constant 20.1994(9) Å at 130 °C. The unit cell resembles a 4  4  4 superstructure of superprotonic CsH2PO4, but features an extraordinary chemical moiety, rotationally disordered H4PO4+ cations, which periodically occupy one of every eight cation sites. The influence of this remarkable cation on the structure, thermodynamics, and proton transport properties of the CPP phase is discussed. Notably, CPP forms at a temperature of 90 C, much lower than the superprotonic transition temperature of 228 C of CsH2PO4, and the compound does not appear to have an ordered, low temperature form. Under nominally dry conditions the material is stable against dehydration to ~ 151 C, resulting in a particularly wide region of stability of a superprotonic material in the absence of active humidification. The conductivity of Cs7(H4PO4)(H2PO4)8 is moderate, 5.8  10-4 S cm-1 at 140 C, but appears nevertheless facilitated by polyanion (H2PO4-) group reorientation.

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Natural Gas Conversion Using Proton-Conducting Ceramic Membrane Reactor
Authors: Ding Hanping , Bian Wenjuan , Wang Lucun , Ding Dong , Zhu Pengxi
Published: July 2021

While the natural gas constitutes a large fraction of fossil hydrocarbon sources, upgrading it to value-added chemical intermediates is crucial for modern chemical industry. While multi-stage industrial indirect conversion via synthesis gas to chemical intermediates dominates the major process, however, the high capital cost still pushes the demand of investing direct conversion path which potentially could reduce the overall cost. Non-oxidative conversion of natural gas to aromatics is a promising chemical process that can synthesize aromatics and hydrogen for downstream conversion processes, which increases process efficiency significantly by improving selectivity and avoiding separation process. In this work, a proton-conducting ceramic catalytic membrane reactor with embedded innovative catalysts is studied for natural gas conversion with higher performance by applying electrochemical potential to overcome the thermodynamic reaction equilibrium. The catalyst candidates are developed to facilitate the high conversion and selectivity towards benzene and other useful olefins with enhanced stability against coking problem. The integration of catalyst into the CMR is also initiated to evaluate the role of hydrogen extraction on improving the aromatics and olefin yielding. The proof of concept is demonstrated to emphasize the great potential of utilizing the renewable electrons into value-added chemicals synthesis.
Ba0.5Gd0.8La0.7Co2O6−δ
Infiltrated BaZr0.8Y0.2O3-δ Composite Oxygen Electrodes for Protonic Ceramic Electrolysis Cells
Authors: Wang Qingjie , Ricote Sandrine , Hendriksen Peter Vang , Wang Yu , Wang Jianqiang , Chen Ming
Published: July 2021

Protonic ceramic electrolysis cells (PCECs) are drawing attention for hydrogen production due to their high efficiency and flexibility, as well as high purity of the produced hydrogen at intermediate temperatures (400-600 ℃). However, one of the major challenges for further improvement of PCECs performance has been the low reaction kinetics at the oxygen electrodes which can lead to high polarization resistances (Rp). In this study, a mixed proton-electronic conducting (MPEC) Ba0.5Gd0.8La0.7Co2O6−

δ
(BGLC) and proton-conducting BaZr0.8Y0.2O3-
δ (BZY20) composite oxygen electrode material was prepared by infiltration and studied as symmetric cells (BGLC-BZY20//BZY20//BGLC-BZY20). The oxygen electrode operating conditions (temperature, oxygen and steam partial pressures) were systematically varied in order to identify and characterize the different electrochemical processes that take place in the oxygen electrode under realistic operation conditions. Two obvious electrode reaction processes were observed in the impedance spectra; the middle frequency one is tentatively ascribed to a charge transfer process and the low frequency one clearly involves oxygen surface exchange reactions. In addition, the results confirm the infiltrated cells exhibit significantly decreased polarization resistance (Rp) and enhanced long-term durability. The polarization resistances increase with pH2O and decrease with pO2. The Rp for infiltrated BZY20 electrodes are 0.44, 1.17 and 2.87 Ω cm2 in 3 % humidified synthetic air (21% O2/79% N2) at 600, 550 and 500 ℃ respectively. In addition, the electrode demonstrated good stability with no detectable degradation within 400 h durability test in 10% humidified synthetic air at 600 ℃. Overall, we conclude that the BGLC infiltrated BZY20 is a promising oxygen electrode material for PCECs operated at intermediate temperatures.
Insights into Interfacial Proton Transport in Protonic Ceramic Conductors
Authors: Meng Yuqing , Gao Jun S
Published: July 2021

Understanding the mechanism of proton conduction at the interface of materials enables the development of a new generation of protonic ceramic conductors at low temperatures (< 300 °C) through water absorption and proton transport on the interface. In-situ Raman spectroscopy was performed on water-saturated, porous, and nanostructured TiO2 membranes directly observe the isotope exchange reactions suggested a Grotthuss-type proton transport and faster isotope exchange rate at 175 °C than that at 25 °C with a corresponding activation energy of 9 kJ mol-1. Comparing to traditional high-temperature protonic ceramic conductors through bulk transport, water absorption on the interface in simple oxides system has higher proton mobility and similar proton concentration, indicating the interface is a facile route for proton transport. In addition, the measured hydrogen isotope exchange rates in nanostructured BCZYYb by in-situ Raman spectroscopy in the temperature range of 100-300 °C were comparable or even higher than that in fully dense BCZYYb in the range of 400-600 °C, suggesting the possibility of using the nanostructured BCZYYb membrane as an electrolyte materials in protonic ceramic fuel cells at low temperatures (<300 °C).
Defect Chemistry of Mixed Conducting Pcfc Cathode Materials with Protons, Oxygen Vacancies and Holes
Authors: Merkle Rotraut , Raimondi Giulia , Hoedl Maximilian F. , Kotomin Eugene A. , Maier Joachim
Published: July 2021

In recent years significant progress was achieved for protonic ceramic fuel cells (PCFC) concerning fundamental understanding, materials processing, and device performance. PCFC cathode materials require sufficient proton conductivity to extend the reaction zone beyond the three phase boundary. The hydration thermodynamics of BaFeO3-
d-related perovskites was studied using thermogravimetry.[1] Despite a high oxygen vacancy concentration, the degree of hydration is lower for cathode materials compared to Ba(Zr,Y)O3-x electrolytes. A partial substitution of iron by redox-inactive, oversized Zn2+ or Y3+ drastically increases the proton uptake. Measurements of oxygen nonstoichiometry and proton uptake indicate pronounced deviations from ideally dilute defect chemistry (assigned to hole-hole and hole-proton defect interactions [1]). Based on DFT calculations [2] and EXAFS/XRS measurements [3], these interactions are related to the partial transfer of electron holes from iron to adjacent oxygen ions, which in turn disfavors protonation. The obtained detailed defect-chemical understanding serves as the basis for further PCFC cathode optimization, in particular since proton uptake, catalytic activity, electronic conductivity, and stability show conflicting dependencies on cation composition.

[1] R. Zohourian, R. Merkle, G. Raimondi, J. Maier, Adv. Funct. Mater. 28 (2018) 1801241.

[2] M.F. Hoedl, D. Gryaznov, R. Merkle, E. A. Kotomin, J. Maier, J. Phys. Chem. C 124 (2020) 11780.

[3] G. Raimondi, F. Giannici, A. Longo, R. Merkle, A. Chiara, M. F. Hoedl, A. Martorana, J. Maier, Chem. Mater. 32 (2020) 8502.

We thank GIF (I-1342-302.5/2016) for financial support.

Figure 1: (a) Increase of proton uptake by Y or Zn doping [1]. (b) Dependence of hydration enthalpy on formal Fe oxidation state [2]. (c) Increased local deformations by Y doping [3]. (d) Conflicting trends; e.g. Ba is beneficial for proton uptake and catalytic activity but detrimental for electronic conductivity and chemical stability.

Figure 1
Assessing Perovskite Electrode Materials Stability for Electrochemical Oxidative Coupling of Methane
Authors: Denoyer Luke H , Ramaiyan Kannan , Benavidez Angelica , Garzon Fernando H
Published: July 2021

Identification of large shale gas reserves has reduced the price of methane significantly. Interest in converting methane to value-added commodity chemicals has increased as a result of these findings [1]. Direct conversion of methane to ethylene using heterogeneous methods such as oxidative and non-oxidative coupling of methane (OCM and NOCM) utilize metal oxide catalysts with varying success. However, a catalyst with commercial viability remains elusive. Recently, iron-doped Sr2Fe1.5+0.075Mo0.5O6-δ electrodes (SFMO-075) have been shown to convert methane to ethylene more efficiently in an electrochemical OCM set up (EC-OCM) [2]. However, one of the main concerns with perovskite electrodes is the stability and durability of these materials. We have developed two different perovskites comprising Ba, Mg, Ca, Nb and Fe and evaluated them for EC-OCM. However, the chemical and electrochemical stability of these materials is largely unexplored. Specifically, during EC-OCM, these materials are exposed to CH4, CO2 and H2O. Each metal oxide’s chemical stability needs to be evaluated under these gases at concentrations relevant to EC-OCM. Further, pure methane supplied at the anode presents a highly-reducing atmosphere, necessitating a study on the redox stability of these materials under very low oxygen partial pressures. We shall report our results on the chemical stability of three different perovskite materials (including SFMO) in EC-OCM relevant conditions. We evaluate these perovskite powders before and after gas exposure using TGA, XPS, XRD and FT-IR measurements. While SFMO was found to be unstable in these conditions with a crystal structure collapse, the other two perovskites show promising stability. Their thermodynamic stability in these conditions along with the feasibility of various reaction mechanisms (analyzed through HSC Chemistry) will be discussed. Our study demonstrates important characteristics of catalysts for EC-OCM and may lend to the design of innovative perovskites capable of converting methane to ethylene electrochemically.

References:

1) P. Schwach, X. Pan, and X. Bao, “Direct Conversion of Methane to Value-Added Chemicals over Heterogeneous Catalysts: Challenges and Prospects,” Chem. Rev., 117, 8497, 2017.

2) C. Zhu, S. Hou, X. Hu, J. Lu, F. Chen, and K. Xie, “Electrochemical conversion of methane to ethylene in a solid oxide electrolyzer,” Nat. Commun., 10, 1173, 2019.
Rational Identification of Doping Strategy to Achieve a Highly Conductive and Reliable Protonic Electrolyte for Electrochemical Cells
Authors: Wang Wanhua , Tang Wei , Ding Hanping , Chen Fanglin (Frank) , Ding Dong
Published: July 2021

While protonic ceramics are being utilized as electrolyte materials in electrochemical cells for hydrogen or electricity production, the higher proton conductivity and chemical stability under realistic operating conditions are required to deliver fast proton flux. For widely used Y or/and Yb doped Ba(Ce,Zr)O3 electrolytes, there are still some concerns with indistinct doping mechanism and uncertain element precipitation problem during sintering, which raise practical problem on electrolyte selection. In this work, the strategy of single element doping and co-element doping has been investigated to understand how they behave differently in proton conductivity and chemical instability. Three compositions, BaCe0.4Zr0.4Y0.2O3-δ, BaCe0.4Zr0.4Yb0.2O3-δ and BaCe0.4Zr0.4Y0.1Yb0.1O3-δ, are chosen to study the overall conductivity as function of B-site environment and gas conditions to provide experimental evidences for composition optimization. More importantly, the Y or/and Yb precipitation in each composition under various sintering conditions is extensively studied to explore the safe window for sintering the electrolyte with minimal element diffusion. In addition, the diffusion of nickel element into the electrolyte grain is also studied to understand the detrimental effects on grain boundary conductivity and consequently the electrochemical performance in the cells. This study will provide some insights into protonic electrolyte selection based on technical considerations on both excellence and stability.
Cu-Sn Gas Diffusion Electrodes Prepared for Continuous Electrochemical Reduction of CO2 to Formate
Authors: He Ruinan , Qiao Jinli
Published: July 2021

Over the past few years, humans excessive use fossil fuels that emission a lot of CO2 result the present energy crisis and earth’s global warming. Efficient conversion of CO2 into liquid fuels has been attracted more interest in recent years. In order to achieve continuous electrochemical reduction of CO2 to formate under ambient conditions the scientific has been made a lot of work. In this work we prepared a Cu-Sn gas diffusion electrodes deposited onto carbon paper by one step. We use a flowing liquid electrolyte reactor to evaluate the Cu-Sn gas diffusion electrodes property. Results shows that the maximum CO2 conversion current density to formate was 50 mA/cm2. Besides, the Cu-Sn gas diffusion electrodes used in electroreduction CO2 for over 10 h. Using one step prepared Cu-Sn gas diffusion electrodes may provide a new pattern into the electroreduction CO2 to alleviate mass transfer limitations and decrease ohmic impedance in electrochemical systems for the synthesis of higher formate by electroreduction CO2.
Dispersed Cu-Sn Nanoparticles Confined in Nanowire Carbon Fibers for Electrochemical CO2 Reduction
Authors: Li Lu Lu , Qiao Jin Li
Published: July 2021

Electrochemical reduction of CO2 (ECRCO2) into useful products, such as formic acid and carbon monoxide, is a fascinating approach for CO2 fixation as well as energy storage. Cu-Sn nanoparticles are attractive catalysts for highly selective ECRCO2 into HCOOH. but still suffer from high overpotential, low current density, and poor stability. Here, a low-cost one-dimensional (1D) Cu-Sn nanoparticle with nanowire carbon fiber (NCF) structure is synthesized and shows superior selectivity for HCOOH products. Using the NCF Cu-Sn nanoparticles as the ECRCO2 catalyst, very high Faradaic efficiency of HCOOH (>96%) can be achieved at a wide potential range from −0.90 to −1.35 V versus RHE, thus substantially suppressing the hydrogen evolution reaction. The electrocatalyst also exhibits excellent long-term stability. The improved catalytic activity of the NCF Cu-Sn nanoparticles indicates that higher surface area and large number of grain boundaries can effectively enhance the ECRCO2 activity. Synthesized via a facile and low-cost electrospinning technology, the reduced NCF Cu-Sn nanoparticles can serve as a promising electrocatalyst for efficient CO2 to HCOOH conversion.
C2H6 Dehydrogenation and Electrical Power Production in a Protonic Conducting Fuel Cell with in-Situ Exsolved Metal Nanoparticle Catalyst
Authors: Li Haixia , Wang Lucun , Wu Wei , Bian Wenjuan , Ding Dong , Chen Fanglin (Frank)
Published: July 2021

In situ exsolution of metal nanoparticles on perovskite framework has been successfully synthesized by reducing the porous precursor SrFe0.55Ni0.2Mo0.25O3−
d(SFMN) in a 5% H2/Ar at 800 °C. Such kind of exsolution not only forms a strong interface between metal nanoparticles and perovskite backbones, but also leads to an increase of oxygen vacancy content in perovskite structure, which will be beneficial to the electrical conduction and catalytic activity towards the oxidations of H2 and C2H6. The BaCe0.4Zr0.4Y0.1Yb0.1O3
−
δ electrolyte-supported proton-conducting single cells have been fabricated using the exsolved metal nanoparticle/oxide fuel electrode catalyst, achieving a maximum output power density of 119.7 mW cm−
2 in H2 and 79.3 mW cm−
2 in C2H6 at 700 °C. Gas compositions using the catalyst in C2H6 have been analyzed using gas chromatography at open circle voltage, demonstrating a C2H4 yield of 1.7% at 700 °C. The promising dehydrogenation activity for C2H6 to C2H4 together with the good electrochemical performance shows this newly developed material may be a potential catalyst for the cogeneration of electrical power and ethylene.