bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving Chemo-Mechanical Stability of Proton-Conducting Perovskites
Authors: Chen Ting , Jing Yuhang , Leonard Kwati , Anderson Lawrence O , Matsumoto Hiroshige , Aluru Narayana R. , Perry Nicola H. 
Published: May 2020

The superior ionic conductivity of selected proton-conducting perovskites enables development of intermediate temperature electrochemical devices, such as solid oxide fuel/electrolysis cells, gas separation membranes, and electrochemical reactors. The lower operating temperature, compared to those of most oxide ion-conductors, can benefit the durability of the devices, as most degradation mechanisms are thermally activated. On the other hand, the chemical strains associated with hydration/dehydration during processing or operation can be considerably larger than those seen in their oxide ion-conducting counterparts during oxygen loss/gain. There is therefore a significant need to develop proton conductors with lower coefficients of chemical expansion (CCE), which is the chemical strain normalized to the change in defect (proton) concentration. Since design principles for engineering CCEs are not well developed, we have previously been investigating the role of various structural and chemical features, such as size of the oxygen vacancy and charge localization.
In this presentation, I will focus on our more recent work investigating the role of octahedral distortions and deviations away from the perfect cubic perovskite structure. By substituting differently sized isovalent cations on the A- and B-site of perovskites, it is possible to engineer the tolerance factor to vary the symmetry and distortions. We have therefore synthesized a series of (Ba,Sr)(Zr,Ce)0.9Y0.1O3-x perovskites with gradually varying tolerance factor. To measure hydration strains, isothermal in situ X-ray diffraction and dilatometry were performed at temperature points in the range ~360-680 °C, in varying humidities. To evaluate the corresponding changes in proton concentration, isothermal thermogravimetric analysis was applied under identical conditions; an intermediate, constant oxygen partial pressure was chosen to avoid the possibility of any simultaneous redox reactions contributing significantly to mass changes and strains. The combined results show that by diminishing the perovskite tolerance factor in this family of zirconate/cerate proton conductors, the coefficient of chemical expansion can be lowered by 500%. Further in situ X-ray diffraction analysis of powder vs. bulk samples, and density functional theory simulations of single crystals, have revealed that there are both crystal chemical and microstructural contributions to the trend seen. The results show that inducing octahedral rotations and lowering symmetry, by altering the cation radius ratio, is an effective route to increase chemo-mechanical stability by lowering CCEs.
Engineering of B-Metal Exsolution for High Performance Anode Materials in Solid Oxide Fuel Cells
Authors: Han Jeong Woo , Kim Kyeounghak 
Published: May 2020

B-metal exsolution has great potential to synthesize well-distributed metal nanoparticles (NPs) on the surface of oxide support materials. In previous works, we found the different exsolution tendencies of different kinds of transition metals on double-layered PrBaMn2O5+δ
(L-PBMO). In particular, the exsolved NPs showed higher catalytic activity and stability for fuel oxidation, such as dry reforming of methane. To further engineer that concept, we have explored the possibility and detailed mechanism for various kinds of B-metal exsolution on L-PBMO. Based on our density functional theory (DFT) results, we will introduce (1) a possible driving force for B-metal NPs exsolution, (2) thermodynamically favorable mechanism for alloy NPs exsolution, and (3) how to boost B-metal exsolution to further improve cell performance SOFCs with the experimental verifications.
In addition to L-PBMO, we also introduce the bond length of B-metal (Co) with lattice oxygen in perovskite structure (Co-doped SrTiO3, STC) as a key descriptor to represent the degree of Co exsolution on STC. Interestingly, we found that the Co exsolution can be facilitated under biaxial tensile strain (larger bond length of Co-O). By examining the bond length of Co-O under different strain states, we demonstrated that the weaker bond strength of Co-O is originated from the larger bond length of Co-O under tensile strain. This results in easier bond breaking between Co and O, thereby facilitating Co exsolution. To confirm our hypothesis (controlling Co-O bond length), we doped the larger ionic radius of A-site cation (Ba) into Sr in STC to induce tensile strain around Co. As we expected, the exsolution of Co is more preferred than than of Ba on STO, which is a more practical way to induce tensile strain than the mechanically applied strategy. As an application of exsolved Co NPs, we showed enhanced catalytic activity for CO oxidation.
(Invited) Ammonia As an Energy Vector
Authors: Soloveichik Grigorii L. 
Published: May 2020

The Advanced Research Projects Agency (ARPA-E) funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency across all economic sectors, and ensure US technological lead in advanced energy technologies, including electrochemical technologies for energy transformation and storage for distributed, grid scale and automotive applications.
Ammonia is produced at a scale of about 180 million tons per year and is easily stored and transported. Currently it is mostly used as a fertilizer and a feedstock for production of various chemicals. However, its physical properties, high energy density, the absence of carbon emissions, availability of feedstock (air and water), and well developed synthesis and infrastructure make ammonia almost ideal energy vector. Produced using renewable energy, it can be used for long duration energy storage and as a zero-emission transportation fuel as well as a hydrogen carrier. To address these technological challenges, ARPA-E launched the Renewable Electricity to Fuels through Utilization of Energy-dense Liquids (REFUEL) program. This program and, in part, OPEN program fund the development of transformational technologies for the conversion of intermittent renewable energy, water and air to energy-dense carbon neutral liquid fuels including ammonia and their conversion to hydrogen or back to electricity using fuel cells. All these directions will be covered in the presentation with emphasis on ammonia fuel cells.
Fuel cells provide the most efficient conversion of ammonia to electricity. Indirect fueling includes the intermediate ammonia cracking to hydrogen (Industrial process runs at 850oC but temperature could be substantially lower with advanced catalysts), which can be purified to PEM fuel cell grade. Direct fueling requires less capital expenses, and can be used with different types of fuel cells (SOFC, PCFC, AEMFC and molten carbonate fuel cells). Performance of direct ammonia fuel cells (DAFC) was demonstrated to be very close to the performance of the same cells fueled by hydrogen (with correction for the dilution). Issues of crossover (for polymer membranes), electrocatalyst stability (nitridation), cell architecture, and operation parameters will be discussed.
Recent advances in the development of novel ammonia synthesis, its use for hydrogen generation, and DAFCs that is being funded by ARPA-E via REFUEL and OPEN 2018 programs will be presented. Comparison of DAFCs with combustion engines fueled by ammonia for energy applications will be given.
(Invited) Electrochemical Nitrogen Reduction to Ammonia on Transition Metal Nitrides
Authors: Xu Bingjun 
Published: May 2020

Renewable production of ammonia, a building block for most fertilizers, via the electrochemical nitrogen reduction reaction (ENRR) is desirable; however, selective electrocatalysts are lacking. Here we show that transition metal nitrides are a family of active, selective, and stable ENRR catalysts. In particular, vanadium nitride nanoparticles have an ENRR rate and a Faradaic efficiency of 3.3 × 10−10 mol s−1 cm−2 and 6.0% at −0.1 V within 1 h,
respectively. ENRR with 15N2 as the feed produces both 14NH3 and 15NH3, which indicates that the reaction follows a Mars−van Krevelen mechanism. Ex situ X-ray photoelectron spectroscopy characterization of fresh and spent VN catalysts reveals that multiple vanadium oxide, oxynitride, and nitride species are present on the surface and identified vanadium oxynitride as the active phase in the ENRR, which is supported by operando X-ray absorption spectroscopic results. Quantitative isotopic label studies are conducted to determine the density of the initial and steady-state active surface N sites.
(Invited) Plasma-Activated Synthesis of Ammonia Using Nitrogen Gas and Water As Feedstocks
Authors: Toth Joseph , Lacks Daniel J. , Renner Julie N. , Sankaran R. Mohan 
Published: May 2020

The reduction of nitrogen to ammonia by the Haber-Bosch (H-B) process entails large energy and environmental costs that motivate research on alternative strategies. A major issue with the H-B process is the need for hydrogen gas that currently comes from fossil fuels (steam methane reforming). Plasma activation is a potential alternative as it was historically the first industrial method employed to fix nitrogen, but by oxidation. More recently, plasmas have been combined with solid catalyst materials to reduce nitrogen to ammonia at lower pressures and temperatures than the H-B process, but also use hydrogen gas as a feedstock.
Here, we present our efforts to develop plasma-activated processes for the reductive synthesis of ammonia using nitrogen and water as feedstocks. One configuration is a hybrid electrochemical system in which a microplasma jet impinging on an aqueous electrolyte surface replaces a metal electrode and reactions are carried out at the interface of the plasma and liquid bath. A second configuration is a hybrid aerosol system in which water droplets are introduced into a larger-volume plasma and reactions are carried out at the interface of the plasma and droplet surface. In both cases, the ammonia is collected in the liquid phase and measured by chemical assay methods. We will discuss process optimization, product selectivity, and energy consumption for both systems. Insights into the reaction mechanisms will also be addressed and in particular, the possible role of water vapor.
(Invited) Direct Ammonia Polymer Electrolyte Fuel Cell
Authors: Wang Teng , Zhao Yun , Achrai Ben , Tamir Gal , Abbasi Reza , Setzler Brian P. , Gottesfeld Shimshon , Yan Yushan 
Published: May 2020

Ammonia is a liquid fuel of high energy density and low storage pressure. These properties facilitate storage, distribution and fueling, as required for the introduction and acceptance of an alternative fuel. Distributed as liquid, ammonia cost is projected to be 30% lower than that of hydrogen distributed as compressed gas.1 The structure of direct ammonia fuel cells (DAFCs) is illustrated in Figure 1a.
The hydroxide exchange membrane employed in our DAFCs work was the poly(aryl piperidinium) (PAP) membrane developed at the University of Delaware2 and at the spin-off company, W7energy LLC. Following optimization of the composition of the catalyst layers and the operation conditions, the performance of an ammonia oxygen cell at Tcell= 95 oC reached the peak power level of 580 mW cm-2 (shown in Figure 1b).
A remaining significant challenge has been the DAFCs performance stability, with testing at constant current showing unstable voltage followed by the fall of the voltage to zero after only a few hours. Recognizing the origin of the instability as liquid management in the DAFCs anode, recent optimization of the anode structure improved substantially the voltage stability with the earliest test showing this improvement, which is depicted in Figure 1c.

1. Y. Zhao, B. P. Setzler, J. Wang, J. Nash, T. Wang, B. Xu, and Y. Yan, Joule, 3, 2472-2484 (2019)
2. J. Wang, Y. Zhao, B. P. Setzler, S. Rojas-Carbonell, C. B. Yehuda, A. Amel, M. Page, L. Wang, K. Hu, L. Shi, S. Gottesfeld, B. Xu, and Y. Yan, Nature Energy, 4, 392–398 (2019)

Figure 1
(Invited) Critical Assessment of Aqueous Electrochemical Synthesis of NH3: N2 Reduction Versus NOx Reduction
Authors: Choi Jaecheol , Suryanto Bryan H R , Du Hoang-Long , Chatti Manjunath , Simonov Alexandr N , MacFarlane Douglas R. 
Published: May 2020

As an ideal alternative to the Haber-Bosch process, the renewable energy-powered electrochemical N2 reduction to NH3 is a promising approach since the electrochemical reduction can occur under mild conditions; only water and N2 are consumed during overall nitrogen reduction reaction.[1] Recently, there have been many efforts devoted to developing electrocatalysts for energy efficient NH3 synthesis from N2; however, it remains very challenging due to the thermodynamic inertness of the dinitrogen triple bond. The electrochemical reduction of N2 to NH3 (the nitrogen reduction reaction “NRR”) requires the consecutive six-electron/proton transfer reactions to proceed and this leads to the sluggish kinetics. In addition, the competitive hydrogen evolution reaction (HER, Eº = 0 V vs. RHE) can concomitantly occur at similar potentials to the NRR (Eº = 0.092 V vs. RHE), resulting in both low faradaic efficiency (< 10 %) and low yield rates (< 10-10 mole cm-2 s-1) for NH3 synthesis. Such poor conversion efficiency and yield rates also make it more difficult to confirm the origins of the NH3 production, ie whether it genuinely comes from electrocatalytic NRR, as opposed to some other readily reducible N-containing contaminants (NO, NO2, N2O and doped N atoms in the materials) under reducing potentials.
Herein, we investigate the catalytic nature of nitrogen reduction reaction on three different types of preeminent electrocatalysts from the literature (bismuth, gold and N-doped carbon)[2, 3] using a rigorous experimental protocol developed by our group.[4] It is demonstrated that all of the catalysts are essentially inactive (below LOD) towards dinitrogen reduction to NH3. We also systematically unravel the origins of the reported activity, showing that other N-containing species, particularly ionic/gaseous NOx or doped N atoms in the materials, are strongly active reactants towards NH3 production. Our presentation will conclude with a summary of the critical contaminants leading to false-positive NRR and also provide further protocol recommendations to avoid this outcome.
[1] S.L. Foster, S.I.P. Bakovic, R.D. Duda, S. Maheshwari, R.D. Milton, S.D. Minteer, M.J. Janik, J.N. Renner, L.F. Greenlee, Nature Catalysis, 1 (2018) 490-500.
[2] Y.-C. Hao, Y. Guo, L.-W. Chen, M. Shu, X.-Y. Wang, T.-A. Bu, W.-Y. Gao, N. Zhang, X. Su, X. Feng, Nature Catalysis, 2 (2019) 448.
[3] Y. Liu, Y. Su, X. Quan, X. Fan, S. Chen, H. Yu, H. Zhao, Y. Zhang, J. Zhao, ACS Catalysis, 8 (2018) 1186-1191.
[4] B.H.R. Suryanto, H.-L. Du, D. Wang, J. Chen, A.N. Simonov, D.R. MacFarlane, Nature Catalysis, 2 (2019) 290-296.
(Invited) Overcoming Technological and Economic Barriers to Generating Renewable Hydrogen with Polymer Electrolyte Membrane Electrolysis
Authors: Mittelsteadt Cortney 
Published: May 2020

Water electrolysis, coupled with green energy sources has long held the promise for supplanting steam methane reforming, SMR, for hydrogen generation for ammonia and petroleum refining, together contributing a billion tons of CO2/year. Additionally hydrogen can be used as a store and carrier of energy for mobile and grid applications. Wide adoption has been prevented by unacceptable costs however, both capital and operating, the latter of which is dominated by the cost of the electricity. In those industrial applications where electrolysis has found a niche it has been dominated by liquid alkaline electrolysis, due to its long history of proven durability and low cost materials. Polymer electrolyte membrane electrolysis (PEMEL) has had the potential to operate at slightly higher efficiencies, and much higher current density, while allowing high, and more importantly, differential pressure. PEMEL’s reliance on precious group metal (PGM) catalysts as well as membrane lifetime concerns have generally left them to specialty applications where footprint is a premium, such as sea and space.
A number of concurrent advancements are overcoming these barriers. First, and most importantly, the cost of energy has come down faster than anyone would have predicted. This cannot be over-emphasized, as will be shown, lowering the cost of renewables has done more for green hydrogen than anything that can be achieved by electrochemical scientists and engineers, as energy costs have long dominated the cost of green hydrogen. Further lowering costs will in turn change focus to capital costs and technology opportunities. Second, improvements in membrane stability has greatly increased the durability of PEMEL systems. This has improved the lifetime of the systems while also allowing more aggressive operating conditions of higher pressure, temperature and current density. The challenges and limitations of further increasing these parameters, as well as their impact on cost will be addressed. Finally, PGM catalyst loadings continue to decrease. This reduction, as well as the increase in lifetimes allows a far greater amount of hydrogen to be generated per gram of PGM catalyst.
The last great barrier for PEMEL to achieve parity with SMR, and enable hydrogen for mobility and large scale energy storage is simply scale. PEMEL, and even alkaline electrolysis are at an infancy in terms of scale. As PEM systems grow from traditional 1-100 kW systems to the 1-100 MW systems necessary for mobility, storage and industrial uses the capital costs will come down tremendously. We will look at how low these costs can go as well as consider the scarcity limitation of PGMs as PEMEL increases capacity from current output of < 100 MW/year to 10-100 GW/year necessary to make real impact in these applications.
(Invited) Manufacturing Challenges and Opportunities for PEM Electrolysis
Authors: Capuano Christopher B , Ayers Kathy , Manco Judith , Wiles Luke , Keane Alex 
Published: May 2020

Hydrogen generation via electrolysis has gained much attention internationally as not only a sustainable source of fuel for the transportation, but as a carrier of energy to capture stranded renewable due to the carbon-free chemical cycle and response characteristics of the technology. The barrier to entry preventing this technology from being widely adopted is the overall cost associated with both the upfront capital expense as well as the operating cost incurred over the product life. The majority of this cost is driven by 1) low electrical efficiencies due to the high ohmic resistance of thicker membranes required by electrolysis systems to electrochemically compress generated hydrogen for storage and the overpotential associated with the water splitting oxygen evolution reaction (OER) catalysts typically used, 2) high cost of system and cell stack materials, which need to be durable for up to 100,000hrs at a potential of 2V in both reducing and oxidizing environments, and 3) the lack of a robust supply chain for high volume manufacturing to further drive down cost through economies of scale.
With 95% of hydrogen currently being produced through the reformation of cheap natural gas, significant cost reductions are necessary for electrolysis to become a viable alternative to the incumbent. Commercial proton exchange membrane (PEM)-based electrolysis has reached scales of several hundred kg/day, providing a relevant pathway for industrial scale hydrogen generation with tremendous opportunity for continuing cost reduction by leveraging system and manufacturing scaling laws by leveraging advancements in PEM fuel cell materials, manufacturing, and analysis tools. Order of magnitude improvements in some of the highest cost elements are easily achievable and with more research funding being directed towards hydrogen production, the realization of these reductions are occurring at a faster rate. While many improvements in stack design and materials of construction have been identified and implemented, there are still numerous opportunities to explore that would move electrolysis towards a viable, cost-effective alternative to natural gas reformation. This talk will describe some of the areas of success, where research is still needed, and ultimately how each of these improvements translate into cost and the path to reformation parity.
(Organic and Biological Electrochemistry Division Manuel M. Baizer Award Address) Making Electroorganic Synthesis More Practical
Authors: Waldvogel Siegfried R. 
Published: May 2020

The direct use of electrochemistry for the generation of reactive intermediates can have major advantages towards conventional synthetic strategies.[1] Less or no reagent waste is generated and new reaction pathways are accessible.[2] In order to exploit the electricity driven conversions for synthetic purposes and to install unique selectivity two modern approaches will be outlined:

Solvent-controlled selective dehydrogenative cross-coupling reactions: A key for this is the use of boron-doped diamond anodes and fluorinated alcohols within the electrolyte.[3] This methodology opened new pathways for innovative and scalable arylation reactions.[4]

New electrode systems for the anodic and cathodic conversion to value-added organic compounds. These systems are capable to go beyond common limits in electro-organic synthesis.

The working horse to identify suitable electrolytic conditions is the electrosynthetic screening approach. This strategy gives also rise to fast optimization and subsequent scale-up.[5] In particular, the second approach will deal with concepts which represent milestones originating from the Baizer process.
References:
[1] E.J. Horn, B.R. Rosen, P.S. Baran, ACS Cent. Sci.
2 (2016) 302-307.
[2] a) S. Möhle, M. Zirbes, E. Rodrigo, T. Gieshoff, A. Wiebe, S. R. Waldvogel, Angew. Chem. Int. Ed. 57 (2018) 6018-6041; b) A. Wiebe, T. Gieshoff, S. Möhle, E. Rodrigo, M. Zirbes, S. R. Waldvogel, Angew. Chem. Int. Ed. 57 (2018) 5594-5619.
[3] L. Schulz, S.R. Waldvogel, Synlett 30 (2019) 275-286.
[4] S.R. Waldvogel, S. Lips, M. Selt, B. Riehl, C.J. Kampf, Chem.
Rev., 118 (2018) 6706-6765.
[5] C. Gütz, B. Klöckner, S.R. Waldvogel, Org. Process Res. Dev. 20 (2016) 26-32.