bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Bioinspired Multi-Scale Pores and Channels
Authors: Hou Xu 
Published: February 2020

"Pores" and "Channels" are everywhere, e.g, from small biological ion channels to large oil pipelines. Pores and channels can be distinguished by the relationship between their diameter and their depth. If the diameter is greater than the depth, the system is treated as pore, otherwise, channel. However, for established porous materials, including membranes, no such strict definition is used. Both, “Pores” and “Channels” have a wide range of significant applications in different scales. Good examples of microscale channels can be found in microfluidics, which has rapidly increasing impact in the areas of chemical synthesis, biomolecule and cell analysis, micro- and nanofabrication, and information technology, etc. With regard to the nanoscale, the nanochannels which led to the birth of a whole new area of research, can be used for nanofluidics, gas separation and storage, batteries, water purification, energy harvest or DNA sorting. In the past, such multiscale pores and channels systems have been intensively explored and contributed to new developments in materials science, in membrane science and technology, or in micro/nanotechnology for analytical, biomedical or information processing applications. Stimulated by the achievements and the even larger potential of multiscale pores and channels systems, increasing research activities are devoted to important aspects such as energy saving, anti-fouling, anti-corrosion, and anti-blocking functionalities, switchability and controllability integration of various different functionalities, and good stability in such confined space. Our research mainly focuses on bioinspired and smart multiscale pore/channel systems, membrane science and technology, microfluidics, interfacial science, physical chemistry, electrochemistry, nano/micro fabrication for energy-saving and biomedical applications.
Recent Publications:

ACS Nano 2018, 12 (2): 908-911;

Nature Communications 2018, 9 (1): 733;

Science Advances 2018, 4 (2): eaao6724;

Small 2018, 1703283;

Small 2018, 1702170;

Nature Reviews Materials 2017, 2: 17016;

Advanced Materials 2016, 28: 7049-7064;

Nature 2015, 519 (7541): 70-73;

CRC Press USA (Book, 2016, ISBN: 978-1-4987-2248-3);

Nano Today 2018 DOI:10.1016/j.nantod.2018.04.006.
Electrocatalytic Hydrogenation of Biogenic Molecules: Understanding Reactivity Trends
Authors: Gutiérrez Tinoco Oliver Y , Sanyal Udishnu , Meyer Laura C , Camaioni Donald M , Lopez Ruiz Juan A , Holladay Jamelyn , Lercher Johannes A 
Published: February 2020

The interest in storing electrical energy into chemical bonds has increased due to the increasing availability of sustainable electricity and its intermittent character. A promising approach is to couple electrolytic H2 production with transformations of organic compounds to chemicals and fuels. Thus, electrocatalytic hydrogenation (ECH) of phenolic compounds, di-aryl ethers and aromatic aldehydes, has been performed on Pt, Pd, Rh, and Ni supported on the working carbon electrodes of H electrolysis cells. At these conditions, H2 evolution (HER) is the prevalent side reaction, thus we define efficiency as the fraction of current used to reduce the organic compounds.

The electrocatalytic hydrogenation of phenolic compounds and aromatic aldehydes readily occur on Pt and Rh, whereas Pd is highly efficient for reduction of aldehydes (Figure 1). The rates of ECH and HER increase with increasingly negative potentials but the efficiency is a strong function of the metal (e.g., Pt and Ni strongly favor HER).
In the conversion of phenolic compounds and ethers, the dominant reaction pathway is hydrogenation to the corresponding alcohols and cycloalkyl ethers. Ether bonds undergo C-O bond cleavage (mainly via hydrogenolysis), which opens pathways to the formation of hydrocarbons. In contrast, aromatic and aldehydes and ketones undergo only reduction of the carbonyl groups without exhibiting any hydrogenation of the aromatic ring. Acidic media accelerates the rates of reduction and enables C-O bond cleavage of alcohols through a bifunctional (acid-metal) mechanism.
We have further studied the effect of solvents in continuous flow systems. Similar to batch H-cells, the aromatic aldehydes are quantitatively converted to aromatic alcohols (Figure 1). The reactivity of these carbonyl compounds is strongly affected by decreasing polarity of the reaction media due to solvation effects. HER is less affected than ECH by increasing the C number of the co-solvent alcohol from methanol to i-propanol. This effect can be compensated by increasing cell potentials (see Figure 1 for the ECH of acetophenone) and the concentration of the reactant.
This study shows that electrocatalysis drives the desired transformations at mild conditions and allows a better control over the reaction pathways than thermal catalysis. Cathodic potentials leads to high rates through increasing the availability of surface H and by providing alternative pathways with low-energy barriers.

Figure 1
Revealing the Atomic Origin of Heterogeneous Li-Ion Diffusion By Probing Na
Authors: Xiao Biwei , Wang Kuan , Xu Gui-Liang , Song Junhua , Chen Zonghai , Amine Khalil , Reed David , Sui Manling , Sprenkle Vincent , Ren Yang , Yan Pengfei , Li Xiaolin 
Published: February 2020

The ion diffusion process, shuttling of Li and Na-ions in and out of the host electrode materials is the basis on which Li-ion batteries (LIBs) and Na-ion batteries (SIBs) operate.[1] Its reversibility and the governing kinetics dictate many of the battery performance parameters such as cycling stability and rate capability.[2] However, it is challenging to understand the ion diffusion process at the atomic level for manipulation in practical rechargeable batteries.[3]
Tracing the dynamic process of Li-ion transport at the atomic scale is a long-cherished wish in solid state ionics and essential for battery material engineering. Approaches via phase change, strain, and valence states of redox species are developed to circumvent the technical challenge of direct imaging Li, however, all are limited by poor spatial resolution and weak correlation with state-of-charge (SOC). Here, we adopt an ion-exchange approach by sodiating the de-lithiated cathode and probing Na distribution to trace the Li de-intercalation, which enables us to visualize the heterogeneous Li-ion diffusion down to atomic level through the utilization of techniques such as scanning transmission electron microscopy - high angle annular dark field (STEM-HAADF) imaging. In the model LiNi1/3Mn1/3Co1/3O2 cathode, dislocation-mediated ion diffusion is kinetically favorable at low SOC and planar diffusion along (003) layers dominates at high SOC, which work synergistically to determine the ion diffusion dynamics. Our work unveils the heterogeneous nature of ion diffusion in battery material and stresses the role of defect engineering in tailoring ion transport kinetics.[4]
References
[1] J. B. Goodenough, Y. Kim, Chem. Mater., 2010, 22, 587
[2] M. S. Whittingham, Chem. Rev., 2004, 104, 4271.
[3] T. Shang and H. Li et al., Adv. Energy Mater. 2017, 7, 1700709.
[4] B. Xiao and X. Li et al., submitted.

Figure 1
Study on Degradation of Microstructure in Ni-Rich Li[NixCoyMn1−x−Y]O2 (x = 0.8, 0.9) Cathodes from Accelerated Calendar Aging
Authors: Ryu Hoon-Hee , Park Kang-Joon , Kim Un-Hyuck , Kim Jae-Hyung , Sun Yang-Kook 
Published: February 2020

Lithium-Ion batteries (LIBs) based on layered transition-metal oxides, Li[Ni
x
Co
y
Mn1
−

x

−

y
]O2 (NCM), have long been considered as an alternative cathode for EVs and the main strategy for increasing the discharge capacity of NCM cathodes has been a progressive increase of the Ni fraction.1,2 However, the large-sized LIBs for EV require not only high energy density, but also longer operation lifetimes and improved safety for more than 10 years. Because an EV is intermittently used, it typically remains stationary for long periods in the fully charged state. Therefore, calendar aging is expected to significantly affect the lifetimes of EVs, similar to cyclic aging. The most common degradations observed from calendar aging in low-Ni NCMs are mainly from the gradual loss of active Li as identified by most researchers.3 However, for Ni-rich NCM materials with high energy densities but poor structural stability originating from phase transitions, the degradation mechanism during calendar aging is still poorly understood.
In this study, we investigated the deterioration of Ni-rich NCM (Ni = 80 %, and 90 %) cathode materials under severe storage conditions.4 To mimic parking conditions for EVs, we performed accelerated calendar aging tests and focused on the consequential structural degradation of the cathode materials upon electrolyte contact.

References

S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett.
2017, 2, 196.

D.-W. Jun, C. S. Yoon, U.-H. Kim, Y.-K. Sun, Chem. Mater.
2017, 29, 5048-5052.

S. Käbitz, J. B. Gerschler, M. Ecker, Y. Yurdagel, B. Emmermacher, D. Andre, T. Mitsch, D. U. Sauer, J. Power Sources
2013, 239, 572.

H.-H. Ryu, G.-T. Park, C. S. Yoon, Y.-K. Sun, Small
2018, 14, 1803179.
Unraveling the Origin of Performance Degradation in High-Capacity Cation-Disordered Oxide Cathodes
Authors: Chen Dongchang , Chen Guoying 
Published: February 2020

Due to the substantial energy gap between state-of-the-art cathodes and anodes, development of new-generation Li ion batteries (LIBs) critically depends on cathode material discovery and improvement. In recent years, a combination of reversible redox activities of both transition-metal cations and oxygen anions were found to be feasible in a number of transition-metal (TM) oxides, such as the layered Li- and Mn-rich, lithium nickel manganese cobalt oxides (LMR-NMCs) and Li-rich rock-salt compounds. Such combination allows a significant enhancement in the charge storage capacity of LIB cathodes. However, challenges exist in these LIB cathodes with both cationic and anionic redox activities. After extensive cycling, performance issues such as capacity fade, voltage decay, hysteresis, and impedance rise often occur. Understanding the chemical origin of these issues in LMR-NMC has been on-going for well over a decade. Various degradation mechanisms, such as TM migrations, have been proposed. However, the effect of oxygen redox in cation-disordered cathode is largely unknown.
In this work, we performed detailed studies on one of the most promising cation-disordered rock-salt cathodes, Li1.3Nb0.3Mn0.4O2 (LNMO). Systematic evaluation on the electrochemical behavior as a function of oxygen redox revealed that the performance deterioration is directly correlated to the extent of oxygen redox involvement. On the fundamental side, we performed a series of hard and soft X-ray absorption spectroscopic (XAS) studies to analyze the changes in Mn and oxygen activities due to cycling, and illustrated the chemical and structural origin for the observed voltage decay and capacity fade. It was found that electrochemical cycling with large contribution of oxygen redox significantly decrease the redox activity of oxygen itself as well as Mn redox activity. In contrast to what was reported on layered LMR oxides, extensive TM reduction was observed but phase transition resulting from cation site migration was not detected in the cycled oxide. A densification/degradation mechanism was proposed accordingly which elucidates how a unique combination of extensive chemical reduction of TM and reduced quality of the Li percolation network in cation-disordered rock-salts can lead to performance degradation in these newer cathodes with 3-dimentional Li migration pathways. On the basis of these studies, cation site chemistry of Li-Nb-Mn rock salt system was systematically tailored to tune the contribution of oxygen redox. Opportunities in balancing capacity and cycling stability will be discussed.
Comsol Simulation of Hierarchical Ordered Porous Microstructure Electrode
Authors: Azami-Ghadkolai Milad , Creager Stephen E , Bordia Rajendra 
Published: February 2020

High specific energy is always desirable in battery systems, especially for electric vehicles. A key towards improving specific energy for a particular combination of anode and cathode active material is to maximize the mass fraction of active material, which means minimizing the fraction of inactive material such as the separator, the binder, electrode additives for improving electronic conductivity, and the current collector. A seemingly simple strategy for maximizing the mass fraction of active materials is to make the electrodes as thick as possible. However, ion transport in thick electrodes can be particularly problematic since salt diffusion into and through the electrode pore space is slow and can easily limit the battery charge / discharge rate.
An ideal microstructure is one that allows for direct line of sight or path for the electrode active material access to the electrolyte, for rapid ion-transport throughout the entire electrode thickness. Therefore, a need exists for electrode fabrication methods that create microstructures that maximize electrolyte transport, as is needed to achieve high-rate charging/discharging in electrodes having high mass loading. Optimal microstructures in electrodes help to achieve the ideal balance of active material and electrolyte mass to give high gravimetric and volumetric energy density.
As to design a microstructure with the goal of Li ion salt transport facilitation, we synthesized ordered porous microstructure electrodes using combination of freeze cast and tape cast techniques. This method enjoys the combination of conventional tape casting, a main technique in manufacturing Li ion electrodes in industrial scale, and freeze casting.
This study simulate two dimensional ordered porous electrode cross-sections and presents the electrochemical performance results of Mo-doped LTO in a electrochemical cell consist of a lithium metal anode, polymer separator, and liquid ethylene carbonate and ethyl methyl carbonate electrolyte. The electrochemical performance of ordered porous microstructure is investigated by varying electronic conductivity, tortuosity, particle size, electrode thickness, and C rate.
We show that these engineered porous electrodes considerably reduces the electrolytes mass transport limitation and electrochemical response of electrode is independent of tortuosity, making it possible to synthesize ultra thick electrode for high energy and power density applications.
Simulation results show that 10 micron thickness of wall and pore freeze tape cast Mo-doped LTO with electronic conductivity of 1 S/m, tortuosity as high as 10, electrode thickness of 458 micron and mass loading of 30 mg/cm^2 can deliver full capacity even at 2 C-rate.
(Invited) Electrodeposited POLY(3,4-ETHYLENEDIOXYTHIOPHENE) (PEDOT) for Invasive Recording and Stimulating Neural Electrodes
Authors: Bodart Côme , Rossetti Nicolò , Cicoira Fabio 
Published: February 2020

Neural electrodes are the best medical technique to alleviate the symptoms of neurodegenerative diseases and to explore of our brains. However, their efficiency is limited by several constraints: their small dimensions lead to high impedance and their rigid and metallic nature coupled with the destructive insertion procedure leads to inflammatory responses in the body that further increases the impedance. Conducting polymers are soft and organic materials that possess a mixed electronic-ionic conductivity, and are ideal candidates for biotic-abiotic interfaces. They are regularly used as coatings for neural electrodes due to their enhancement of electrochemical properties and their believed biocompatibility. The dominant technique to deposit conducting polymers on neural microelectrodes is electropolymerization. Extensive work as being performed on the optimization of the parameters of this deposition method. Still, electrodeposited conducting polymers coatings suffer from poor adhesion on most of their substrates. Besides this issue, there is a lack of long-term in vivostudies confronting conducting polymer coatings to electrical stimulation conditions used in medical applications.
In this work, we investigated the influence of the processing solvent for electropolymerization on the stability and the adhesion of conducting polymer coatings. After having defined a precise deposition procedure providing us with stable coatings, we investigated the usefulness of these coatings for in vivodeep brain stimulations.
Poly(3,4-ethylenedioxithiophene) (PEDOT) was electropolymerized in three different solvent: acetonitrile, propylene carbonate and water, on platinum-iridium microelectrodes. The coated microelectrodes were subjected to different stability tests: sonication, passive ageing, steam sterilization, and electrical stimulations in vitro. We found out that acetonitrile and propylene carbonate provided the most resistant PEDOT coatings. Still, all of PEDOT coatings processed in the different solvents were stable enough to be used in a medical context. We therefore implanted PEDOT-coated stimulating microelectrodes in rats and applied daily stimulation all the while monitoring the impedance of the microelectrodes. We observed that electrical stimulations decreased the impedance of both the PEDOT-coated microelectrodes and the uncoated control microelectrodes. The decrease in impedance was more important for the control microelectrodes than for the PEDOT-coated ones, which questions the relevance of PEDOT coatings for deep brain stimulation purposes and indicates that more work is required to obtain a performant conducting polymer coating for stimulating neural electrodes.
MoS2/NiS2 Composites for Efficient Hydrogen Evolution Both in Acidic and Alkaline Media
Authors: Hu Jue , Zhang Chengxu 
Published: February 2020

The growing concern about global warming, environmental pollution and energy security has raised the demand for clean energy resources in place of fossil fuel. Cost-efficient generation of hydrogen from water-splitting through electrocatalysis holds tremendous promise for clean energy (1, 2). Central to the electrocatalysis are efficient and robust electrocatalysts composed of earth-abundant elements, which are urgently needed for realizing low-cost and high-performance energy conversion devices. Transition metal compounds (TMCs) are a group of attractive noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER). Earth-abundant MoS2 has emerged as a promising hydrogen evolution reaction (HER) catalyst with high activity and durability, but it is kinetically retarded in alkaline media . Extensive efforts have been devoted to improving the HER activity of MoS2 in acid (3), but little attention has been paid to simultaneously enhancing its HER performance both in acid and base. This work demonstrates a dramatic enhancement of HER kinetics both in acidic and alkaline media by hybridizing vertical MoS2 with another earth-abundant material, nickel disulfide (NiS2). Field-emission SEM image shows that the MoS2/NiS2 composite is composed of a film-like structure of NiS2 cover on the edge surfaces of the MoS2 sheets (Figure 1a). As shown in Figure 1b, the XRD peaks observed at 2θ=14.1°, 32.9° and 58.8° of the MoS2/NiS2 sample can be indexed to 2H-MoS2 crystal (JCPDS No. 75-1539), and peaks at 2θ=31.4°, 45.1° and 53.4° indexed to (200), (220) and (311) facets of the NiS2, respectively (JCPDS No. 88-1709). The synthesized MoS2/NiS2 composite exhibits a much lower HER overpotential both in acidic and alkaline media than that of bare MoS2 and NiS2 catalysts (Figure 1c and d).
Figure caption
Figure 1. (a) FESEM image of the MoS2/NiS2 composite. (b) XRD patterns of the NiS2 and MoS2/NiS2 samples, together with the standard pattern of 2H MoS2 (JCPDS 75-1539) and NiS2 (JCPDS 88-1709). (c) Polarization curves of bare MoS2, NiS2 and MoS2/NiS2 composite catalysts in 0.5 M H2SO4 solution at a scan rate of 5 mV/s. (d) Polarization curves of bare MoS2, NiS2 and MoS2/NiS2 composite catalysts in 1 M KOH solution at a scan rate of 5 mV/s.

References

D. Strmcnik et al., Improving the hydrogen oxidation reaction rate by promotion of hydroxyl adsorption. Nat. Chem.
5, 300-306 (2013).

Y. Jiao, Y. Zheng, M. T. Jaroniec, S. Z. Qiao, Design of electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions. Chem. Soc. Rev.
44, 2060-2086 (2015).

J. Hu et al., Engineering stepped edge surface structures of MoS2 sheet stacks to accelerate the hydrogen evolution reaction. Energy Environ. Sci.
10, 593-603 (2017).

Figure 1
Enhanced Electrochromic Properties of a Nickel Oxide-Alanine Film
Authors: Wang Ke-Hsuan , Ikeuchi Hayato , Kawai Takeshi 
Published: February 2020

Electrochromic materials can change their color under the application of an electrical voltage. The color change accordingly upon charge insertion/extraction, which induce in the material a process of redox reaction. Electrochromic materials are expected to serve an important role in efficient energy applications to control the brightness of light. High optical contrast, fast switching speed, and good cycling durability are required for an electrochromic material to function as a practical material in a device. These properties are influenced by the morphology of the electrochromic film and the associated changes in local ionic diffusion.
In this work, we report a facile and cost-efficient preparation of electrochromic materials which are formed by assembly of nano-sized clusters of nickel oxides by electrodeposition integrating amino acids. Electrodeposited films were characterized using Raman spectroscopy, in situ X-ray absorption fine structure spectroscopy, and atomic force microscopy to determine the electronic and structural changes in the films during coloration. These results indicate that the structure of the nickel oxide films in their oxidized state is similar to γ-NiOOH, regardless of kinds of integrated amino acids, although the grain size of the films is dependent on kinds of integrated amino acids. The different grain size results in significant differences in electrochromic performance. The film made of small grain size exhibits the best electrochromic performance. This study demonstrates that a suitable integration of amino acid is essential to enable sustained electrochemical activity, reactive site formation, and functional stability.

Figure 1