bluuebunny/crossref_metadata_2025 huggingface dataset:
(Digital Presentation) Large–Scale High-Performance Low Catalyst Loaded Membrane Electrode Assemblies for Advanced Proton Exchange Membrane Water Electrolyzers
Authors: Zeng Zhiqiao , Bliznakov Stoyan , Bonville Leonard J. , Ouimet Ryan J. , Niedzwiecki Allison , Capuano Christopher , Ayers Katherine E. , Maric Radenka
Published: July 2022

Hydrogen is regarded as the next-generation energy carriers for the future hydrogen economy.1 Among the hydrogen production technologies, proton exchange membrane (PEM) water electrolyzers is considered the favored approach for the implementation of the global hydrogen energy transformation due to its several benefits including high power density operation, low ohmic losses and differential pressure operation. However, (i) high cost mainly from the high platinum group metals (PGM) loading in the catalysts layers; (ii) low durability due to instability of the catalysts layers and membrane; and (iii) poor safety because of hydrogen crossover of PEM water electrolyzers have jeopardized their widespread commercialization. Currently, a new Department of Energy Consortium (H2NEW) has targeted hydrogen production from electrolysis, especially PEM water electrolysis, for use as a clean, sustainable fuel, which can achieve $2/kg hydrogen production cost by 2025.2 This requires a balance between the performance, durability and scale-up cost of membrane electrode assemblies (MEAs) for PEM water electrolyzers.

In this work, we demonstrate the capability to fabricate large scale MEAs by the unique Reactive Spray Deposition Technology (RSDT), that have one order of magnitude lower PGM loadings in the catalyst layer than the state-of-the-art (SOA) designs, and activity and durability performance comparable to the SOA commercial MEAs. RSDT is a flame-based method that combines the catalysts synthesis and electrodes deposition processes into one step and thus substantially reduces the time and cost for their fabrication.3–5 The RSDT fabricated MEA with 680 cm2 geometric area electrodes, and loadings of 0.2 mgPt/cm2 in the cathode and 0.3 mgIr/cm2 in the anode has been tested at current density of 1.8 A cm-2, 50 oC, and 400 psi differential hydrogen pressure. The initial steady-state test for over 250 hours, clearly shows excellent activity and stability. In addition, the RSDT fabricated MEA has integrated dual recombination layers that effectively reduce the hydrogen crossover to below 10 %LFL at all current densities from 0.58 to 1.8 A/cm2.

Reference

1. M. Carmo, D. L. Fritz, J. Mergel, and D. Stolten, Int. J. Hydrogen Energy, 38, 4901–4934 (2013).

2. https://www.energy.gov/sites/default/files/2021-09/h2-shot-summit-panel1-lte-status.pdf

3. H. Yu et al., Appl. Catal. B Environ., 239, 133–146 (2018) https://doi.org/10.1016/j.apcatb.2018.07.064.

4. H. Yu et al., Electrochim. Acta, 247, 1155–1168 (2017) http://dx.doi.org/10.1016/j.electacta.2017.07.093.

5. G. Mirshekari et al., Int. J. Hydrogen Energy, 46, 1526–1539 (2021) https://doi.org/10.1016/j.ijhydene.2020.10.112.
(Digital Presentation) Effects of Catalyst Dimension Parameters on Local Oxygen Transport in Cathode Catalyst Layer of Proton Exchange Membrane Fuel Cell
Authors: Li Xiang , Tang Fumin , Li Bing , Dai Haifeng , Chang Guofeng , Ming Pingwen
Published: July 2022

Improving the performance of proton exchange membrane of fuel cell (PEMFC) can save materials and then reduce costs, which is helpful to accelerate its large-scale commercial application. In this paper, an agglomerate model is proposed and developed by coupling a one-dimensional local oxygen transport model with a one-dimensional multiphase non-isothermal fuel cell model to study the influence of catalyst dimension parameters (Pt radius, Pt average dispersity, carbon radius) on local oxygen transport in the cathode catalyst layer (CCL) comprehensively. And this elaborate model shows that the smaller Pt radius, carbon radius, and the higher Pt average dispersity can reduce the transport distance of oxygen molecules from the pores to the active sites, and then decrease the local resistance. Based on the above understanding, the performance of the optimized cell with a Pt loading of 0.2 mg cm-2 is improved by 22%, slightly higher than the original cell with a Pt loading of 0.4 mg cm-2, which achieves a 50% reduction in Pt loading while maintaining the cell performance. This research will give a guide for improving cell performance.
(Keynote, Digital Presentation) Environmental Remediation and Conversion of Pollutants to High-Value Chemicals by Integrated Adsorption-Separation-Electrocatalysis Processes
Authors: Lu Jian-Mei
Published: July 2022

With rapidly growing industrial and economic activities, low-level pollutants, such as nitrate, urea, etc. in air, surface and ground water, have been increasing due to release of fertilizers and pesticides from industry, agriculture, and domestic sewage. It is promising to remove these pollutants and subsequently produce high-value chemicals by electrocatalysis but suffers from low efficiency. Recently, we have exploited several strategies, such as the built-in-electric field, local coordination symmetry, enhanced adsorption-separation interface and substrate geometry, to modulate the microenvironment of active sites on electrocatalysts, facilitating interfacial accumulation of the low-concentration pollutants. These have resulted in remarkable enhancement of the pollutant removal efficiency as well as improvement of yield of high-value products. In this talk, we will report our progress in separation and electrocatalytic removal of low-concentration pollutants and conversion of pollutant to high-value products.
(Digital Presentation) Characterization of Ultrafast Dynamics of Refractory Metal Nanoparticles of Interest as Photocatalysts
Authors: Wiederrecht Gary P. , Govorov Alexander
Published: July 2022

Plasmonic noble metal nanoparticles are of interest as photocatalysts for several reasons, including a very large absorption cross section and the creation of a greatly enhanced evanescent electromagnetic field at the surface of the nanoparticles when excited at the plasmon resonance. Furthermore, the plasmon resonance is tunable over a wide wavelength range as a function of the size, shape, and composition of the nanoparticles. When these properties are combined with the known photocatalytic activity of noble metals for technologically important targets such as solar fuels, it is not surprising that these nanoparticle systems are widely studied. Noble metals do, however, possess a weakness in that they can be easily melted upon photoexcitation, due to the fact that noble metals dissipate absorbed photon energy efficiently through ultrafast electron-phonon coupling, in roughly one picosecond, to produce heat. As a result, the study of new classes of plasmonic materials, such as refractory metals, with much higher melting points than noble metals is growing rapidly. While there are still challenges in the size-selective synthesis of refractory metal nanoparticles, characterization efforts on these materials are of strong interest. We report here a study on the time-resolved spectroscopy of electron-phonon coupling in refractory metal nanoparticles. There are very significant variations in the efficiency and time-scales of electron-phonon coupling in refractory metal nanoparticles as compared to noble metal nanoparticles. Furthermore, due to the fact that many refractory metals are oxidized under ambient conditions to create a thin oxide layer on the surface of the nanoparticles, these materials also demonstrate dynamics related to electron injection from the metal to the oxide layer that noble metals do not show. Far from being a negative, the added electron injection dynamics offer new opportunities for photocatalysis that we discuss. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
(Digital Presentation) Energy Resolved Dynamics of Mid-Gap and Surface States in ZnTe Photocathodes
Authors: Cushing Scott
Published: July 2022

Transient x-ray spectroscopy has become a powerful tool for photoelectrochemistry. X-rays can measure the coupled electronic and structural dynamics that underlie excited state polaron formation, molecular reaction dynamics, and hot carrier thermalization pathways. Element-specific responses can be used to measure electron or hole transport between each component of a photoelectrode (i.e. light absorber, oxide protection layer, catalyst). In this talk, we discuss how improvements in the signal to noise ratio of our transient XUV spectrometer now allow for the measurement of mid-gap and surface state filling dynamics. The energy of electrons and holes as a function of time is measured for a ZnTe photocathode. The thermalization, mid-gap state filling, and recombination are measured in terms of the energies of electrons and holes. An ab-initio approach using the Bethe-Salpeter equation with time-dependent electron and phonon populations is used to predict and confirm the transient XUV measurements. The few nanometer surface sensitivity of grazing angle, transient XUV measurements make it favorable for measuring interfaces in photoelectrochemistry.
Effects of Sn and Nb Doping on the Performance of Fe2TiO5 As a Water Splitting Photocatalyst
Authors: Melo Mauricio A. , Goncalves Renato Vitalino
Published: July 2022

Very recently, pseudobrookite Fe2TiO5 has been revealed as a promising photocatalyst for the oxidation half-reaction of overall water splitting. This semiconductor is inexpensive, non-toxic, possesses a relatively small band gap, and presents improved structural and photochemical features compared to other well-known photocatalysts. In this investigation, we doped the Fe2TiO5 structure with 1.0 at% tin and 1.5 at% niobium, separately, through a solvothermal method to prolong the minority carrier diffusion length and reduce charge recombination events under visible light illumination. The procedure generated single-phase Sn- and Nb-doped Fe2TiO5 nanoparticles with dimensions close to 30 nm. In both cases, optical band gap values of 2.1 eV were observed. Pristine Fe2TiO5, Sn-doped Fe2TiO5, and Nb-doped Fe2TiO5 were irradiated by a Xe lamp (λ>400 nm), producing 59.2, 297.6 and 344.0 mmol h-1 g-1 of O2, respectively. This result reflects the substantial improvement that doping Fe2TiO5 with Sn and Nb confers to its photocatalytic water splitting activity. In addition, photoelectrochemical measurements in a 1 M NaOH electrolyte indicated photocurrent increments from 2.4 mA cm-2 at 1.23 VRHE, for the pristine Fe2TiO5, to 36.7 and 70.7 mA cm-2 at 1.23 VRHE for Sn- and Nb-doped Fe2TiO5, respectively, accompanied by overpotential drops of 0.04 and 0.1V. Electrochemical impedance spectroscopy indicated that reductions in the resistance for the charge carrier transfer resistance at the solid/liquid interface plays an important role for the performance improvement of the doped nanomaterials. Overall, this work illustrates how structural alterations of a potential photocatalyst can improve photochemical energy conversion. The authors acknowledge support from FAPESP (Grant 2017/11986-5) and Shell and the strategic importance of the support given by ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation.
Screening Ruddlesden-Popper (n=1) Oxide Materials for Thermochemical Water Splitting By Density Functional Theory
Authors: Wilson George E. , Seymour Ieuan , Cavallaro Andrea , Skinner Stephen , Aguadero Ainara
Published: July 2022

Thermochemical redox reactors store concentrated solar power by thermally inducing an oxygen deficiency within a metal oxide structure. The metal oxide’s affinity for reoxidation allows it to facilitate the splitting of H2O or CO2 to produce H2 or CO for syngas formation.[1] Typically, high temperatures (>1400 °C) are used to drive the reduction of the benchmark material, CeO2, [2] however there is motivation to lower this temperature and investigate new metal oxides capable of larger fuel productions. Perovskite materials have been thoroughly investigated due to their crystallographic stability and ability to accommodate relatively large oxygen deficiencies. Emery et al. [3] conducted a wide computational screening of this family of materials based on a few simple thermodynamic parameters originally proposed by Meredig and Wolverton. [4]

Herein, we extend these previous studies and investigate the A2BO4 Ruddlesden-Popper (RP) oxides family [5], layered perovskites, that have previously demonstrated fast redox kinetics and large oxygen storage as solid oxide fuel cell cathodes.[6] A combination of screening parameters based on charge neutrality, Goldschmidt tolerance and computed defect formation energy, identified 38 possible RP candidate materials. One of which - Ca2MnO4-δ – was taken forward to experimental testing due to its Earth abundant elements. The powder was synthesized via a modified Pechini method and thermal analysis experiments demonstrated thermally driven oxygen evolution from 800 to 1200 °C equating to a non-stoichiometry of δ=0.18. High-temperature X-ray diffraction alluded to the formation of a CaMn2O4 secondary phase above 1075 °C, therefore consequent thermochemical water splitting cycles were carried out at a maximum of 1000 °C. Oxidation under steam at 800 °C demonstrated good hydrogen production volumes, although gas production on further cycles was limited by particle sintering observed by scanning electron microscopy. Further investigations aim to understand and improve the cyclability and kinetics under different reaction temperatures and humidity. This study outlines, with experimental validation, how computational screening can be used to find future suitable RP candidates for thermochemical water splitting whose performance can be further improved with doping strategies and morphological adaptation.

References

[1] Scheffe J. R. and Steinfeld A., Materials Today, (2014), 17, 341-348

[2] Chueh W. C., et al., Science, (2010), 330, 1797–1801

[3] Emery A., et al., Chem. Mater. (2016), 28, 5621−5634

[4] Meredig B. and Wolverton C., Phys. Rev. B: Condens. Mater. Phys. (2009), 80, 245119.

[5] Ruddlesden S. N. and Popper P., Acta Crystallogr., (1957), 10, 538-539

[6] Ghorbani-Moghadam T., et al, Ceram. Int., (2018), 44, 21238–21248
(Invited) Photoelectrochemical Energy Materials and Device
Authors: Kang Soon Hyung
Published: July 2022

Nowadays, the exploration of new photoelectrode architectures to improve the light-harvesting and charge-collection properties of photoelectrochemical cells and related devices have been regarded as a challenging work. The efficient, stable, visible light absorption and cost effective photoelectrode materials are certainly important in developing highly efficient PEC system. Here, we synthesized the various metal oxide and nitrides for photoelectrochemical water splitting. Based on their synthesis methods and intrinsic properties, we tested the possibility(large-scale and stability) toward their PEC applications. Related deep insight would be discussed in terms of the fundamental analyses and reasonable results based on the theoretical background to give an meaningful potential for the future PEC world.
Tandem Electrochemical Conversion of CO2 to Liquid Fuels and Chemical Feedstocks
Authors: Kang Mavis , Kolb Manuel , Calle-Vallejo Federico , Yeo Boon Siang Jason
Published: July 2022

Increasing demand for energy has led to a high dependence on fossil fuels, which are limited and have been closely associated with major environmental issues such as groundwater pollution and imbalances in the carbon cycle. A more sustainable and cleaner method of producing chemicals and fuels is the electrochemical CO2 reduction reaction (CO2RR). When coupled with renewable electricity, CO2 can be converted to high energy density fuels and commodity chemicals, such as ethanol, propanol, and ethylene, in an environmentally friendly way.

Recently, the use of CO feedstocks, instead of CO2, was shown to enhance the selectivity toward multi-carbon products on copper-based electrocatalysts. Technoeconomic analyses have also demonstrated that CO can be produced from CO2RR cost-effectively. This has led to increased efforts in developing tandem electrocatalytic systems. However, state-of-the-art CO2-to-CO electrocatalysts are based on expensive noble metals such as Ag and Au, while earth-abundant Zn displays relatively poorer selectivity and activity. Herein, we show that oxide-derived Zn with high surface area can reduce CO2 to CO with a Faradaic efficiency of 86% and a partial current density (j
CO) of −201 mA cm-2. While oxygen vacancies were previously implicated for CO2RR to CO, we pinpointed by detailed experiments and density functional theory calculations that highly undercoordinated Zn sites provide even higher activity, in view of their nearly optimal *COOH adsorption energies. These findings indicate that suitably engineered ZnO-derived materials can potentially be an alternative to the more costly Ag and Au electrocatalysts, and that the main guideline for their design is to increase the undercoordination of the catalytic sites.

We also investigate the electrochemical CO reduction reaction (CORR) to liquid fuels and industrial feedstocks on copper-based and mixed copper-silver catalysts. To further enhance the CORR activity and product selectivities, a systematic optimization of the experimental environment, such as the use of various supports, catalyst binder and electrolytes, was done. We develop a set of experimental conditions for optimal CORR performance to value-added products.
Electro-Chemical-Mechanical Coupled Modeling of Oxygen Electrodes in Solid Oxide Electrolyzer Cells
Authors: Jin Xinfang , Jayapragasam Puvikkarasan , Wen Yeting , Huang Kevin
Published: July 2022

Solid oxide electrolyzer cell (SOECs), which is an electrochemical device to split water with electricity to generate hydrogen, have received widespread attention for multi-day or seasonal energy storage to integrate variable renewable energy (VRE) into the grid [1]. Even though there have been tremendous material development and performance improvement of the technology in the past decade [2], challenges remain in understanding its degradation mechanism, especially the delamination of oxygen electrode/electrolyte interface [3-5]. Developing new oxygen electrodes which could decelerate the degradation and extend the stack lifetime beyond 60,000 hours at 1.5A/cm2 would significantly drive the stack price down to $100/kW and hydrogen cost down to $2/kg [6].

In the state-of-the-art SOECs, pure ionic conductor 8 mol% Y2O3 doped ZrO2 (YSZ) and Gadolinium-doped Ceria (GDC) are usually used as the dense electrolyte and the buffer layer; mixed electronic and ionic conductor (MIEC) La1-xSrxCo1-yFeyO3-d (LSCF) is widely used as the oxygen electrode [7]. Such cells still suffer from short lifetimes with current densities over 1A/cm2. To overcome the challenge, a bilayer oxygen electrode structure, consisting of a commercial LSCF-GDC porous backbone coated by a thin SrCo0.9Ta0.1O3-
d (SCT10) film (denoted as LSCF-SCT bilayer design), has been proposed and demonstrated with much higher performance compared to traditional LSCF electrode (single layer design) [8]. The new oxygen electrode has an inherently fast oxygen evolution reaction (OER) electrokinetics (or high oxygen evolution rate) and can mitigate the delamination problem by minimizing the accumulation of oxygen in oxygen evoluation reaction (OER) electrode lattice and thus chemical stresses.

In this study, based upon an Electro-Chemical-Mechanical coupled model, we will correlate the crack length at the oxygen electrode/electrolyte interface with the electrochemical performance of the cell, specifically the voltage-current curve (Fig.1a). We will use J-integral (Fig.1b) as the fracture criteria to evaluate the crack growth rate under different current densities and with different oxygen electrode designs. LSCF single layer design is the baseline of the study. The long-term performance improvement of LSCF-SCT bilayer design will be compared against the baseline and its degradation mechanism will be investigated. The model will also be validated by long-term overpotential testing data as a function of time under 1A/cm2. It will be used as an optimization tool to mitigate delamination and extend the cell lifetime under higher current densities.

Key Words: Electrolysis, Oxygen Electrode (OE), Delamination, Chemical Expansion, J integral, Crack Growth Rate

Figure 1
(Invited, Digital Presentation) Yet Another Symmetry Breaking in Electromechanical Materials
Authors: Pryds Nini
Published: July 2022

The wide range of fascinating properties observed in complex oxide continue to attract great interest such as ferro-, piezo- and pyroelectricity. Several strategies have been employed to break the lattice symmetry and expand the range of functionalities. Electrostriction is a general property of all dielectrics and occurred when the deformation of a dielectric material is proportional to the square of the applied electric field. Recently, Gd2O3-doped CeO2 (CGO) has emerged as a new family of electrostriction materials with the maximum stress exceeding 500 MPa. To date, various efforts have been made to improve the strain output, such as stimulate by electric field, varying the temperature and aging the defects. However, materials that simultaneously satisfy the requirements of fast response, large strain and high energy density are still very rare. The development of materials with large dielectric breakdown strength, high dielectric constant and low elastic modulus is still challenging.

Heterostructure interfaces plays an important role by contributing to its unique structural and physical properties which result in symmetry breaking, electronic and/or atomic reconstruction(s) as well as strain gradients from which a wealth of new intriguing properties can emerge. Such richness arises from a strong interaction between the charge, orbital, spin, and lattice degrees of freedom.

Here, I will show how symmetry breaking offers extraordinary opportunities such as stabilizing phases which are otherwise not stable using highly coherent interfaces and enhancing the electromechanics with interfaces or inducing piezoelectricity in otherwise centrosymmetric system. In one example I will show the results obtained with a stack of ultrathin defective oxide single-crystal layers with stable phases and electrostriction properties exceeding any known system. Alternating layers of Gd2O3-doped CeO2 (CGO) and Er2O3-stabilized δ-Bi2O3 (ESB) were deposited on NdGaO3 substrates. The measured electrostriction coefficients found to follow a linear increase with the decrease of the number of interfaces. We have observed the highest electrostriction coefficient which surpasses any known electrostrictive materials, including the commercial relaxor ferroelectrics, such as PMN-PT. In another examples I will show our recent discovery illustrating the possibility to induce a large piezoelectric response in centrosymmetric oxides, i.e., in cubic fluorite oxides, Gd-doped CeO2-x. Surprisingly, the results show the generation of large low-frequency piezoelectric responses (d33 ~ 100,000 pm/V). Such a high piezoelectric response from intrinsically nonpiezoelectric materials has not been observed before in centrosymmetric materials.

This collection of possibilities offers unique opportunities for a wide range of rich world and new functionality of complex oxide and their interfaces.
(Digital Presentation) Understanding the Rate Limiting Process in a Pulse Laser Deposited Thin-Film Double Perovskite Electrode for Oxygen Reduction Reaction
Authors: Dhongde Vicky , Anjum Uzma , Kumar Ajay , Dhaka Rajendra , Haider Mohammad Ali , Basu Suddhasatwa
Published: July 2022

Oxygen reduction reaction (ORR) in a double perovskite material is considered to be the most sluggish reaction in the intermediate temperature operation of a solid oxide fuel cell (SOFC). ORR is often inhibited by poor oxygen surface exchange rates or bulk diffusion in the material. In order to understand the rate-limiting process of the material, we have fabricated a dense thin-film double perovskite of composition Sr2CoNbO6-
δ. The pulse laser deposition (PLD) method is employed to fabricate geometrically well-defined symmetric electrodes of SCN on an electrolyte substrate for accurate assessment of electrode impedance. Electrode thickness is varied from 40 nm to 80 nm by changing the deposition parameters in PLD. On increasing the thickness, the electrode impedance is observed to increase, suggesting bulk diffusion of oxygen anions limiting the electrochemical performance in the electrode material.
Combining Operando Techniques to Probe Chemo-Mechanical Evolution at Buried Solid/Solid Interfaces
Authors: Marbella Lauren , Chang Wesley , May Richard , Wang Michael , Sakamoto Jeff , Steingart Daniel A.
Published: July 2022

Chemical and mechanical changes local to the electrode/electrolyte interface critically impact performance in all-solid-state batteries. Unfortunately, the dynamics at electrochemical interfaces are exceptionally challenging to probe in all-solid-state batteries because these changes take place across multiple length scales (from the nano- to meso-scale) and are buried within the system (at the solid/solid electrode/electrolyte interface). Here, I show our efforts to couple operando acoustic transmission measurements with nuclear magnetic resonance spectroscopy and imaging to correlate changes in interfacial mechanics with the growth of Li microstructures and the solid electrolyte interphase (SEI) in a non-invasive, multimodal fashion. Specifically, we study chemo-mechanical changes at the interface between Li metal anodes and Li7La3Zr2O12 solid electrolytes as a function of stack pressure and current density.
A Study of Stress Evolution and Deformation in Cylindrical Cells, from before Manufacturing to End of Life
Authors: Holloway Justin , Balart Murria Maria , Loveridge Melanie J
Published: July 2022

The mass production of lithium-ion cells involves applying a range of manufacturing processes to a range of materials. These processes inevitably result in residual stresses within the individual materials, which when abetted by operational stresses can cause deformation and fracture of the componentry. This contributes to the degradation of electrochemical properties, device performance, and durability of the cells; leading ultimately to cell failure. This experimental study is concerned with determining the mechanical degradation of componentry within cylindrical cells. Mechanical degradation was evaluated for commercial cells using x-ray tomography, mechanical testing and microscopy. Nanoindentation testing was used to characterise mechanical changes in the foil material in three conditions: before cell manufacture, after cell manufacture and after aging. This work represents a novel ex situ characterisation tool and a new approach to understanding degradation in electrochemical systems. Additionally, we anticipate this work to aide modelling of and controlling degradation within electrochemical systems.
(Invited) Engineering Interfaces in Solid-State Polymer-Ceramic Composite Electrolytes of Li-Ion Batteries
Authors: Wu Nianqiang , Yang Hui
Published: July 2022

This talk presents our effort to engineer interfaces in solid-state polymer-ceramic composite electrolytes of lithium-ion batteries. A Grafting agent has been utilized to strengthen the polymer-ceramic interface. Also, a Li-ion conducting buffer layer has been employed to enhance interaction between the ceramic nanofibers and the polymer matrix. In addition, dopants and oxygen vacancies in ceramics can enhance interfacial interaction.
(Invited) Operando Measurement of Heterogeneities in All-Solid-State Li Battery Electrodes
Authors: Gallaway Joshua W
Published: July 2022

All-solid-state Li batteries are under intense research and development due to their potential to (a) replace flammable organic liquid electrolytes with solid materials, and (b) increase energy density by allowing Li metal anodes and resulting in a more compact battery.[1]Several types of Li+-conducting solid electrolytes are being studied, e.g. sulfides, oxides, phosphates, polymers, and various composites of these.[2] While polymers are very processable, they have low conductivities, generally <10-4 S/cm. Sulfides have high conductivities, >10-2 S/cm, but are unstable materials and require cells to be under high compression to get good cycling results.[3] Oxides and phosphates have good conductivity, but are hard and brittle, forming poor interfaces with electrode active materials. The ideal combination of solid electrolyte and active material remains elusive, but work continues.

An additional challenge looms for the design of all-solid-state electrodes, as reaction distributions in battery electrodes are often heterogeneous, resulting in uneven utilization of active materials.[4] Uneven reaction distributions are generally the result of an imbalance between electronic and ionic transport in the cell, but can also be caused by other resistances such as those introduced by insulating layers surrounding active materials. In this talk I will report our experimental results measuring heterogeneous phenomena in all-solid-state batteries. We have employed electrochemical impedance spectroscopy (EIS) as well as energy dispersive X-ray diffraction (EDXRD). EDXRD is a high-energy synchrotron technique that allows the interiors of batteries to be profiled in a tomographic way during battery operation. We use this to directly observe heterogeneous lithiation gradients across the thickness of cathodes in all-solid-state batteries. We will focus on cells with sulfide electrolytes, such as Li6PS5Cl and Li6.6Ge0.6Sb0.4S5I. Heterogeneous structural stability of the electrolyte itself will also be discussed.[5]

Acknowledgments

We acknowledge financial support from the National Science Foundation under Award Number CBET-ES-1924534.

References

[1] J. Janek and W. G. Zeier, "A solid future for battery development," Nat Energy, vol. 1, no. 9, pp. 1-4, 2016.

[2] J. C. Bachman et al., "Inorganic solid-state electrolytes for lithium batteries: mechanisms and properties governing ion conduction," Chem Rev, vol. 116, no. 1, pp. 140-162, 2016.

[3] Y. Kato et al., "High-power all-solid-state batteries using sulfide superionic conductors," (in English), Nat Energy, vol. 1, Mar 21 2016.

[4] J. S. Newman and C. W. Tobias, "Theoretical Analysis of Current Distribution in Porous Electrodes," J Electrochem Soc, vol. 109, no. 8, pp. C193-C193, 1962.

[5] X. Sun et al., "Operando EDXRD Study of All‐Solid‐State Lithium Batteries Coupling Thioantimonate Superionic Conductors with Metal Sulfide," Advanced Energy Materials, vol. 11, no. 3, p. 2002861, 2021.
Oxide Films and Nanoparticles for Lithium Ion Battery and Oxygen Electrocatalyst Applications
Authors: Luo Hongmei , Zhou Meng
Published: July 2022

The global energy crisis coupling with the consumption of fossil fuels and the associated environmental issues, has stimulated extensive interest in searching for clean, efficient and sustainable energy storage and conversion systems. In this talk we are going to introduce a novel chemical solution approach for epitaxial thin film deposition and oxide nanoparticle network synthesis. The use of water soluable polymer to bind the metal ions has several advantages. The formation of covalent complexes between the lone pairs on the nitrogen atoms of the polymer and the metal cations make it possible to prepare almost any metal polymer precursor solutions. The unique chemistry and processing design of this technique deliver stable and homogeneous solutions at a molecular level that allows epitaxial growth of high-quality thin films and oxide nanoparticle network materials. Oxygen electrocatalysis, including both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), dominates the performance of the devices. However, the sluggish kinetics of these two reactions limits their performance. Therefore, development of non-precious metal-based oxygen electrocatalysts is greatly demanded. Metal oxides have attracted extensive interest as alternative electrocatalysts due to their low price and good endurance under relatively high temperature, which can be doped with a wide range of cations attributed to their flexible compositions and structures, leading to easy manipulation of their electrocatalytic properties. We study the nanoscale engineering of perovskite oxides and layered oxides in energy conversion/storage devices and focus on the electrode catalyst design and fabrication for boosting ORR and OER electrocatalysis.
(Keynote) Degradation Processes in Solid Oxide Cell Ni-YSZ Electrodes
Authors: Barnett Scott A , Zhang Qian , Grimes Jerren , Cox Dalton , Hong Junsung , Park Beom-Kyeong , Yang Tianrang , Voorhees Peter W.
Published: July 2022

Solid oxide cells (SOCs) can have a significant impact on climate change over the next decade and beyond, in applications such as balancing renewable grid electricity via electrolytic fuel production, and producing electricity from bio-fuels combined with CO2 product sequestration. However, long-term performance degradation remains a key variable that may limit further implementation of SOCs. This talk focuses on the Ni-YSZ fuel electrode that is widely used but is known to be an important contributor to SOC degradation. Various processes that cause Ni-YSZ degradation are discussed. Results on 3D tomography measurements of accelerated Ni coarsening are described and a quantitative model is developed to predict long-term degradation. Although the results indicate that coarsening effects can be minimized in well-designed Ni-YSZ microstructures, degradation can still occur, especially during high-current-density electrolysis operation. For operation under low H2O/H2 conditions, high electrolysis current density can yield reduction of zirconia to form Ni-Zr compounds, along with substantial microstructural damage. For operation under high H2O/H2conditions, high electrolysis current density can yield Ni migration away from the electrolyte. A phase-field simulation is described that predicts this Ni migration, using actual Ni-YSZ microstructures measured using 3D tomography as the starting point, and compared with experimental observations. The model assumes that Ni transport is driven by a spatial gradient in surface tensions, i.e., a decrease in the Ni/YSZ contact angle with increasing distance from the electrolyte. Recent results on electrolysis and reversibly operated SOCs, making use of Ceria-infiltrated Ni-YSZ to improve stability, are described.
(Keynote) Theoretical Analysis of Electrochemical Stability in a Solid Oxide Cell
Authors: Zhou Xiao-Dong
Published: July 2022

In this talk, I will describe a theoretical analysis and modeling of electrochemical stability in solid oxide cells, including solid oxide fuel cell, solid oxide electrolysis, and solid-state batteries. Focus will be on elucidating the origin for the electrochemically driven of phase change and the deposition of neutral species at the interfaces and inside a solid electrolyte.
(Invited) Chemical Stability and Performance of Rare Earth Nickelate Oxygen Electrodes for Reversible Solid Oxide Cells
Authors: Gopalan Srikanth , Akter Ayesha
Published: July 2022

Composite rare-earth nickelate-rare-earth doped ceria oxygen electrodes have inherent chemical instabilities. Over the last year, we have made progress on achieving chemical stability and high performance using a strategy of heavily doping the ceria phase with rare-earth cations. A higher dopant concentration of a rare-earth cation in the ceria phase ensures thermodynamic stability of the nickelate phase in contact with the ceria phase. In particular, composite oxygen electrodes comprising lanthanum nickelate La2NiO4+δ (LNO) - lanthanum doped ceria (LDC) and neodymium nickelate Nd2NiO4+δ (NNO) - neodymium doped ceria (NDC) have been electrochemically tested in both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes. The performance of these cells have been compared to a composite strontium doped lanthanum manganite (LSM)-8 mol% yttria stabilized zirconia (YSZ) electrode. Both nickelate based electrodes achieve far superior performance compared to the LSM electrodes. We also report impedance measurements from symmetrical cells featuring LNO and NNO electrodes, analyzed using a distribution of relaxation times (DRT) approach. The DRT analysis reveals significant differences in the rate controlling steps in oxygen reduction and incorporation steps between the two materials. Lastly, oxygen surface exchange results for LNO and NNO are also reported which show different oxygen exchange kinetics when measured on dense versus porous materials which have implications for deploying these materials in reversible solid oxide cells.
One-Pot Synthesis of MnO2/Reduced Graphene Oxide Via Hydrothermal Routes for Supercapacitor Applications
Authors: Lee Hyejin Jin , Noor Navid , Gumeci Cenk , Higgins Drew
Published: July 2022

Manganese dioxide (MnO2) is a promising supercapacitor electrode material due to its high theoretical capacitance, low cost and environmental compatibility. However, the electrochemical performance of MnO2 is often limited by low electrical conductivity of MnO2. The MnO2/carbon composites have been successfully demonstrated as an effective way to improve overall electrical conductivity of MnO2 based materials.

In this study, we report MnO2/reduced graphene oxide (rGO) composites for high performance supercapacitor applications. The MnO2/rGO composites exhibited 381F/g at a charge/discharge current density of 5 A/g, which was significantly higher as compared to that of pure MnO2 (140 F/g at a charge/discharge current density of 5 A/g). This result indicates that improved capacitance of the MnO2/rGO composites benefited from the incorporated rGO properties, such as high electrical conductivity and large surface area.
Facet-Dependent Selectivity of Cuprous Oxide/Silver Tandem Catalysts for Promoting C2H4 Production from Electrochemical CO2 Reduction
Authors: Geng Dongsheng , Dong Gang
Published: July 2022

The over-exploitation of fossil fuels and the consequent increase of atmospheric CO2 concentration have aroused people's attention to energy and environmental issues.(1) In terms of reducing CO2 content, the electrocatalytic CO2 reduction reaction (CO2RR) can effectively solidify CO2 and convert it into high value-added chemicals. There are many CO2RR reduction products, including CO, HCOOH, C2H5OH, CH4,C2H4, etc.(2) However, in the CO2RR process, the hydrogen evolution reaction (HER) in the water phase has a lower reduction potential, making the CO2RR products less selective, which has become the most important problem restricting its practical application. Therefore, improving the selectivity and activity of CO2RR products has important research significance and practical application value.

In this work, a series of Cu2O/Ag nanocrystals (NCs) with different crystal faces were prepared by hydrothermal method. Specifically, cubic Cu2O (c-Cu2O) enclosed with {100} facets, rhombic dodecahedral Cu2O (d-Cu2O) enclosed with {110} facets, and octahedral Cu2O (o-Cu2O) enclosed with {111} facets, are mixed with Ag nanospheres to form c-Cu2O/Ag, d-Cu2O/Ag, and o-Cu2O/Ag bimetallic tandem catalysts. The catalysts can improve the high activity and selectivity of CO2RR to produce C2H4 product by adjusting different crystal faces. We can find from Figure 1 that o-Cu2O/Ag tandem catalyst exhibits an impressive Faradaic efficiency (66.8%) and partial current density (17.8 mA cm-2) for C2H4 product at -1.2 VRHE. This result provides a new strategy for improving the selectivity of CO2RR to produce C2+ products by adjusting the crystal facet engineering.

Figure 1. (a) SEM images of o-Cu2O/Ag, (b) LSV curves of three Cu2O/Ag catalysts in Ar and CO2-saturated 0.5 M KHCO3 solutions, (c) Partial current density of C2H4 formation on the three Cu2O/Ag catalysts at -1.2 V, (d) Faradaic efficiencies of C2H4 on the three Cu2O/Ag NCs.

Reference

[1] P. De Luna, C. Hahn, D. Higgins, S. A. Jaffer, T. F. Jaramillo and E. H. Sargent, Science, 364 (2019).

[2]Y. Zheng, A. Vasileff, X. Zhou, Y. Jiao, M. Jaroniec and S. Z. Qiao, J Am Chem Soc, 141, 7646 (2019).

Figure 1
Water-Assisted Electrochemical Ammonia Synthesis on Electrospun Cobalt-Molybdenum Carbide Composite
Authors: Chung Sunki , Ju Hyungkuk , Lee Jaeyoung
Published: July 2022

The electrochemical synthesis of ammonia under ambient condition has attracted significant attention as an alternative route for green ammonia production. However, competing hydrogen evolution reaction (HER) hinders selective ammonia synthesis through electrochemical nitrogen reduction reaction (NRR). For the broad adoption of such technology in industries, it is essential to overcome poor selectivity of NRR by developing effective electrocatalysts and controlling the reactant at the interface between electrode and electrolyte.[1,2] In this study, we prepared cobalt-molybdenum carbide-carbon nanofiber via electrospinning method as a selective NRR catalyst. Furthermore, we reveal the relationship between water adsorption ability and NRR selectivity on biphasic catalyst using isotopic-labeling and in-situ analyses.

Reference

[1] Journal of Electroanalytical Chemistry
2021, 896, 115157.

[2] Journal of Energy Chemistry
2022, 67, 474–482.
Ex-Situ Investigation of Membrane Swelling in an Electrolyzer Using X-Ray Tomography
Authors: Hoppe Eugen , Holtwerth Sebastian , Müller Martin , Lehnert Werner
Published: July 2022

In this contribution, we focus on the membrane swelling of a catalyst coated Nafion© 212 in the compound of a polymer electrolyte membrane electrolyzer. So far, the swelling of the catalyst coated membrane (CCM) is mostly investigated isolated from the surrounding components as porous transport layers (PTL) and the flow field plates[1-4]. To explore the swelling, ex-situ tests were carried out, using a special device [5] to control contact pressure and compression and computer tomography. This allowed the swelling of the CCM to be studied at different positions in the structure and at different compression pressures as well as the interaction of the different components. Figure 1 shows a comparison of the dry (a) and (c) and flooded (b) and (d) state of the CCM. The black lines indicate the surface of the CCM. In the flooded state, the thickness of the CCM increases by 20 % from about 50 µm to 60 µm, while the distance of the expanded metal sheets stays constant. This means, that the thickness increase of the CCM results in a decrease of at least one PTL thickness. One main goal of the experiment was to show, whether the swelling of the membrane is dependent or independent of the compression pressure and therefore may cause a different water uptake, which might give an explanation of the decreasing high frequency resistance with increasing pressure [4, 6].

[1] Ito, H., Maeda, T., Nakano, A., & Takenaka, H. (2011). Properties of Nafion membranes under PEM water electrolysis conditions. International journal of hydrogen energy, 36(17), 10527-10540

[2] Budinski, M. K., & Cook, A. (2010). Osmotic pressure of water in Nafion®. Tsinghua Science & Technology, 15(4), 385-390

[3] Kusoglu, A., Kienitz, B. L., & Weber, A. Z. (2011). Understanding the effects of compression and constraints on water uptake of fuel-cell membranes. Journal of the Electrochemical Society, 158(12), B1504

[4] Borgardt, E., Giesenberg, L., Reska, M., Müller, M., Wippermann, K., Langemann, M., Lehnert, W., & Stolten, D. (2019). Impact of clamping pressure and stress relaxation on the performance of different polymer electrolyte membrane water electrolysis cell designs. International journal of hydrogen energy, 44(42), 23556-23567

[5] Hoppe, E., Janßen, H., Müller, M., & Lehnert, W. (2021). The impact of flow field plate misalignment on the gas diffusion layer intrusion and performance of a high-temperature polymer electrolyte fuel cell. Journal of Power Sources, 501, 230036

[6] Stähler, M., Stähler, A., Scheepers, F., Carmo, M., Lehnert, W., & Stolten, D. (2020). Impact of porous transport layer compression on hydrogen permeation in PEM water electrolysis. International journal of hydrogen energy, 45(7), 4008-4014

Figure 1
(Invited) Evaluation of Steam Splitting (OER) Kinetics in Praseodymium-Based Perovskite Thin Film Electrodes for Efficient Intermediate-Temperature Water Electrolysis
Authors: Lee Jongmin , Perry Nicola H
Published: July 2022

Water electrolysis at high temperatures (> 600 ˚C) provides both kinetic (no precious metals) and thermodynamic (lower voltage requirement) benefits for hydrogen generation. However, recently steam electrolysis at intermediate temperatures (300 - 600 ˚C) has attracted attention, given potentially faster startup times, ready access to waste heat, and mitigation of some degradation modes, while maintaining some of the high temperature benefits. Intermediate-temperature electrolysis can be accomplished with protonic ceramic electrolysis cells (PCECs), for which a primary challenge is the need for efficient, chemically stable, and long-term durable oxygen/steam electrodes. Electrode material candidates tend to be perovskite-based oxides that must be triple conductors, enabling transfer of oxide ions, protons, and electronic species for PCECs. While Barium (Ba) containing perovskite (ABO3) oxygen electrodes are an active focus due to their low hydration enthalpies enabled by the basicity of Ba, their poor long-term stability and non-optimized catalytic activity hinder the practical deployment of PCECs. Additionally, segregation of large cations (e.g., Ba, Sr) often takes place on electrode surfaces, which further hinders their catalytic performance and long-term stability. Thus, we have been investigating synthesis and performance of lower-Ba or Ba-free oxygen/steam electrodes and relating these to the evolution of the surface chemistry during operation.

In this work, we fabricated Pr-based perovskite oxides, including Pr(Ga,Mg)O3-x, Ba(Pr,Y)O3-x, and others, as thin films with well-defined geometries and surface areas using pulsed laser deposition and compared their performance to the standard Ba(Co,Zr,Fe,Y)O3-x. Considering the multiple valence states (3+, 4+) of Pr and its large size, which may lead to surface segregation, the inclusion of Pr, or even replacement of Ba with Pr, is hypothesized to benefit catalytic activity and stability. We examined the surface water splitting/ hydrogenation coefficients (k-values) using electrical conductivity relaxation with pH2O steps, as a function of time and gas atmosphere. Further investigations of the role of crystalline quality, composition, and thickness have been made to understand the factors controlling the thin film electrode activity and stability. Our results of quantitative k-values on well-defined surfaces can guide design of high performance steam/oxygen electrodes and understanding of degradation mechanisms impacting performance of PCECs.