bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of Porous Anolytes for Rechargeable Metal Batteries
Authors: Thomas-Alyea Karen E. 
Published: February 2020

Recently there has been great interest in porous lithium metal electrodes for rechargeable batteries, which have demonstrated remarkable improvements in cycle life and charge-rate capability compared to planar lithium metal [1]. In this type of cell design, the porous electrode consists of a porous solid electrolyte with void space in the discharged state. During charge, the metal plates onto the surface of the solid electrolyte, filling the pores. During discharge, the pores empty as lithium reacts at the surface of the electrolyte to produce lithium ions which travel through the porous electrolyte. The electrolyte is rigid, so its shape remains fixed over the life of the cell. This design is advantageous because the solid-electrolyte interphase (SEI) is stationary on the surface of the electrolyte, and therefore there is little capacity fade over cycling, because there is no volume change to cause cracks in the SEI. The design also allows space for the metal to deposit into, thereby reducing the cyclic stress of depositing metal pushing against the separator. By reducing the stress of the lithium pushing against the separator, the risk of a dendrite growing through a defect in the separator is reduced.
Here we present an electrochemical model for a cell with a porous anolyte based on porous-electrode theory [2], and apply the model to optimize the design of the porous anolyte to maximize cycle life and safety. For example, we find that, because the electronic conductivity of lithium metal is over 7 orders of magnitude higher than the ionic conductivity of present state-of-the-art solid electrolytes, electronically conductive additives provide no benefit for the porous electrode. As the lithium plates onto the electrolyte surface (initially at the interface with the current collector), the plated lithium itself provides a sufficiently electronically conductive network. Furthermore, if the area-specific resistance of the porous electrode is too low, the current distribution can be highly nonuniform, which can have deleterious consequences for cycle life and safety. Finally, we discuss the implications of the model for the necessary mechanical properties of the solid electrolyte to prevent dendrites even in the presence of manufacturing tolerances.
References
[1] C. Wang, Y. Gong, B. Liu, K. Fu, Y. Yao, E. Hitz, Y. Li, J. Dai, S. Xu, W. Luo, E. D. Wachsman, and L. Hu, NanoLetters 2017, 17(1) p. 565.
[2] J. Newman and K. E. Thomas-Alyea, Electrochemical Systems, 3rd edition, Hoboken: John Wiley & Sons, Inc., 2004.
Uniform Distribution of Sn Nanoparticles in Carbon Matrix As Anodes for High-Performance Lithium-Ion Batteries
Authors: Han Weiqiang , Ying Hangjun , Xin Fengxia 
Published: February 2020

Abstract

Presently, nanocrystallization and carbon composite modification are two main strategies to mitigate the volume change of Sn and prolong the cycle life. Nanoscale Sn can reduce the absolute volume change and suppress the volume mismatch in a single granule and the particle breakage is significantly inhibited. Moreover, the small size can shorten the ions diffusion distance in the material and improve dynamic performance. Carbon is the ideal material to modify Sn anodes. On one hand, the soft and flexible carbon works as “buffer zone” to hold the volume change and inhibit the particles aggregation. On the other hand, it serves as the conductive network to accelerate the ions transport and electrons transfer, as a result, improving the rate capability of Sn based materials.
Taking the advantages of nanoscale Sn and carbon modification, we recently designed nano-Sn/reduced graphene oxide (Sn/RGO) composites with extra small Sn particles uniformly dispersing in the carbon matrix. The 3D few-layer stacked Sn/RGO composite shows a structural evolution phenomenon from a stratified structure to a curly Sn@Carbon nanocage-like structure after cycling. The nanocage-like Sn@C structure is stable and guarantees the ultralong cycle life of Sn/RGO. It can steadily cycle up to 1000 times without obvious attenuation at 0.2 C, the specific capacities remain stable above 550 mAh g-1.
Figure 1. Schematic illustration of structural evolution of Sn/RGO during cycling

Acknowledgments

This work is supported by the National Natural Science Foundation of China (Grant No. 51371186), the “Strategic Priority Research Program” of the Chinese Project Academy of Science (Grant No.XDA09010201), Ningbo 3315 International Team of Advanced Energy Storage Materials, Zhejiang Province Key Science and Technology Innovation Team (2013TD16).

Figure 1
Metal-Assisted Chemical Etching of GaAs Using Au Nanodots
Authors: Imai Ryota , Hashimoto Hideki , Asoh Hidetaka 
Published: February 2020

III-V compound semiconductors have attracted attention as next-generation materials and potential alternatives to silicon-based semiconductors because of their excellent properties including superior carrier mobility and direct band gap. In a previous study, we fabricated microbump arrays of InP [1] and line patterns and pillar arrays of GaAs using metal-assisted chemical etching [2]. However, the dimensions of the resultant patterns ranged from several micrometers to several tens of micrometers. To the best of our knowledge, no study has reported the formation of ordered GaAs nanostructures with submicron-scale or smaller periodicity using metal-assisted chemical etching. Thus, we attempted to clarify the etching mechanism of GaAs on the nanometer scale. In this study, we investigated the effects of etchant composition and temperature on the morphology of the etched GaAs during metal-assisted chemical etching using Au nanodot arrays as a catalyst. A through-hole porous alumina mask with an ordered array of openings was set on an n-type GaAs. Subsequently, a 20-30 nm thick Au layer was evaporated through the alumina mask using a mixed vacuum deposition system. The periodicity of Au nanodot arrays, which were formed on GaAs substrate, was 100 nm and the diameter of Au dot was 50-60 nm corresponding to the dimensions of anodic alumina mask. After the formation of Au dot arrays on GaAs substrates, the specimens were immersed in a mixed solution of HF and KMnO4. When the specimen was etched in a HF containing relatively low concentration of KMnO4 at high temperature, Au dots sank into the GaAs substrate. The positive holes (h+), which were generated by reduction of oxidant (i.e., KMnO4) at Au surface, are thought to be consumed immediately at the Au/GaAs interface. As a result, Au dot arrays sank into the substrate, resulting in the formation of pore arrays. On the other hand, in the case of high concentration of KMnO4, h+ diffused into the surrounding Au-coated GaAs; thus, site-selective etching occurred on the exposed GaAs surface. Attempts to clarify the effects of the concentration of oxidizing agent on the generation of h+ and morphology of etched are currently underway.
[1] H. Asoh, T. Yokoyama and S. Ono, Jpn. J. Appl. Phys., 49, 046505 (2010).
[2] H. Asoh, Y. Suzuki and S. Ono, Electrochim. Acta, 183, 8-14 (2015).
The Electrochemical Activity of Nitrogen Doped Graphene Towards Oxygen Reduction Reaction in Ionic Liquid at Intermediate Temperature
Authors: Puthen Peediyakkal Hasna , Kikuchi Syojiro , Yu Jie , Munakata Hirokazu , Kanamura Kiyoshi 
Published: February 2020

Among the various types of fuel cells, polymer electrolyte membrane fuel cells (PEFCs) have attracted much attention as future electrical energy production system due to its high power density and wide range of applications in portable and stationary devices. The properties of commonly used perfluorosulfonate polymer membranes like Nafion®limit the operating temperature of PEFCs upto 80 ⁰C resulting the difficulty in heat and water management, CO poisioning of catalyst and its low electrochemical activity.
Recently proton conducting ionic liquids, particularly N,N-diethymethylammoniumtetraflurosulfonate (dema-TfO) have attracted much attention as electrolytes enabling the fuel cell operation at intermediate temperature above 100 ⁰C. In fact, prototypes of intermediate temperature fuel cells using dema-TfO have been developed by some research groups including us1,2. As increasing the operating temperature, the electrochemical activity of catalyst increases which can expand the selection of electrode catalysts.
Carbon-based nanostructures have been confirmed to be excellent materials for enhancing oxygen reduction reaction (ORR) for conventional PEFCs with perfluorosulfonate polymers3. In this study, we have synthesized nitrogen-doped graphene (NG) by simple pyrolysis of graphene oxide (GO) and urea mixture at 900 ºC under Ar atmosphere as an ORR catalyst for intermediate temperature fuel cells using ionic liquids. The oxygen reduction activity of NG has been studied using a rotating disc electrode in dema-TfO under N2 and O2atmosphere at different temperatures. The ORR onset potential and current density shifted to positive and increased with increasing temperature. The comparison with pristine graphene at 120 ⁰C (Fig. 1) clearly indicated the positive effect of nitrogen doping on the improvement of ORR activity. Although the ORR activity of NG was still lower than that of commercially available Pt/C (37.5%), it has excellent electrochemical stability. The durability test was measured based on the protocol of the Fuel Cell Commercialization Conference of Japan (FCCJ). Even after 2000 cycles in the potential range of 1.0 to 1.5 V vs. RHE, NG retained almost the same onset potential, which is much higher durable than those of Pt/C (~ 15.6 % loss).

Reference

1. S.-Y. Lee, A. Ogawa, M. Kanno, H. Nakamoto, T. Yasuda and M. Watanabe, J. Am. Chem. Soc., 132, 9764 (2010).
2. M. Haibara, S. Hashizume, H. Munakata and K. Kanamura, Electrochim. Acta, 132, 208 (2014).
3. Z. Lin, G. Waller, Y. Liu, M. Liu and C.-P. Wong, Advanced Energy Materials, 2, 884 (2012).

Figure 1
Self-Assembly- and Preshaping-Assisted Synthesis of Ultrathin Nitrogen-Doped Graphitic Carbon Lamellas Supported Molybdenum Carbide for Hydrogen Evolution Reaction
Authors: Peng Lishan , Zhang Ling , Shen Jingjun , Wei Zidong 
Published: February 2020

The sustainable generation of hydrogen through water electrolysis by using electricity has attracted great attention but remains an elusive goal in catalysis. Metallic carbide have been ardently expected to be the most promising alternatives to replace or reduce Pt employment in electro-catalyze HER.[1,2] Herein, we report a “self-assembly and preshaping” strategy for the controllable synthesis of porous graphitic carbon lamellas supported highly dispersed Mo2C nanoparticles (Fig. 1a-c). The self-assembly and preshaping not only efficiently promoted the distribution of Mo2C on the highly conductive carbon nanolamellas, but it also impeded the aggregation and excessive growth of ultrafine Mo2C nanoparticles at high temperatures. These features enabled the full exposure and utilization of the Mo2C active sites for H+ adsorption and reduced the electrical resistance between neighboring surface-Mo2C, endowing the constructed Mo2C/C-lamellas with a superior HER activity and long-term stability compared with traditional bulk Mo2C/C. As a matter of course (Fig. 1d-g), relative to traditional Mo2C/C-bulks, the as-constructed Mo2C/C-lamellas exhibits higher activity for the HER with a lower onset overpotential (145 mV), a smaller Tafel slope (60.5 mV dec-1), better electroconductivity, and improved stability over 20 h during operation in 0.5m H2SO4. This self-assembly and preshaping assisted carburization method represents a rational strategy for the preparation of robust carbon composite materials with hierarchically ordered structures, especially high melting point and easily-aggregation compound.
Figure 1. (a) Schematic illustration of the synthetic procedure of Mo2C/C lamellas; (b,c) TEM images of Mo2C/C lamellas; (d,e) Linear Sweep Voltammetry curves and Tafel plots during HER over 20 wt% Pt/C, SA-C, Mo2C/C bulks and Mo2C/C lamellas; (f) Current density vs. time (I–t) curve of HER over Mo2C/C lamellas at I=10 mA over 20 h-long electrocatalytic reaction; (g) Polarization curves of Mo2C/C lamellas before and after ageing.
Reference:
[1] M. S. Dresselhaus, I. L. Thomas, Nature
2001, 414, 332-337.
[2] W.-F. Chen, J. T. Muckerman, E. Fujita, Chemical communications
2013, 49, 8896.

Figure 1
Controlled Synthesis of Hollow Micro/Meso-Pore Nitrogen-Doped Carbon with Tunable Wall Thickness and Specific Surface Area As Efficient Electrocatalysts for Oxygen Reduction Reaction
Authors: Wu Rui , Chen Siguo , Wei Zidong 
Published: February 2020

Here, we demonstrate a rational design and preparation of hollow micro/meso-pore nitrogen-doped carbon (HMNC) catalysts with micro-, meso-, and macroporosity integrated into one structure through high temperature pyrolysis of the precursor containing polydopamine (PDA) coated silica spheres and FeCl3. The TEM and BET analysis results show that the wall thickness and specific surface area of HMNC can be simply controlled by adjusting the Fe content absorbed on PDA. The ORR activities have a strong correlation with the specific surface area and the wall thickness of the HMNC electrocatalysts. The optimized HMNC catalyst with ~5 nm wall thickness and 1703.5 m2 g-1 specific surface areas showed highest ORR performance, which was comparable with Pt/C in both the reaction current and the initial potential in alkaline media. The remarkable ORR activity is ascribed to its unique hollow micro/meso-pore structure, which can provide shortest diffusion channels for oxygen and electrolyte as well as a high specific area and sufficient exposure of inner-pore catalytic sites. This work provides an important guidance to other researcher in designing and fabricating high performance N-doped carbon electrocatalysts for industrial purposes that range from catalysis and sensors to supercapacitors and lithium-ion batteries.

Figure 1
Synthetic Melanin Films As Potential Interfaces for Peroxynitrite Detection and Quantification
Authors: Kalil Haitham , Kay Clara , Al-Mahmoud Ousama , Bayachou Mekki 
Published: February 2020

Peroxynitrite (PON) is a highly reactive oxygen-nitrogen species that facilitates both oxidation and nitration reactions. PON is the primary product of the reaction of superoxide anion-radical with nitric oxide radical. It has been well established that PON is a major noxious molecule, which is implicated in a host of pathophysiological conditions. Recently, PON has emerged as a new member of the nitroxidative array of reactive metabolites. Early clinical reports have emphasized the deleterious physiological reactivity of PON with many cellular targets including DNA, proteins, and lipids at cell/tissue levels.
Melanin is a natural pigment that has many physiologic functions including the neutralization of highly reactive oxidative species. Tyrosine and its derivative 5,6-dihydroxyindole (DHI) are precursors of eumelanin, a brown or black forms of melanin that is also photo-stable. Recent studies have suggested that melanin can act as antioxidative therapy to scavenge reactive oxygen and nitrogen species including PON.
In this project, we examine the chemical interaction between synthesized PON and polymerized films of DHI as a model of synthetic melanin. First, we studied the electrochemical characteristics of polymerized 5,6-dihydroxyindole on graphite electrodes, and then monitored the changes after adding aliquots of PON. This part of the work reports primarily on chemical changes within the electro-polymerized films of melanin on the electrode. We also studied the rates of chemical decay of PON in the presence of the transparent Indium Tin Oxide (ITO) electrodes coated with melanin films using absorbance spectroscopy. Ultraviolet-visible spectroscopy showed a significant difference between the decomposition rates of PON alone and in the presence of DHI films. The melanin films were characterized with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) to image and determine the surface chemical composition of the synthetic film. X-ray Photoelectron Spectroscopy (XPS) has been used to detect and analyze the change on the synthetic melanin films coated ITO slides before and after exposure to PON. Finally, we report on the possibility of using DHI films as a platform for the quantitative detection of PON in solutions using amperometry and impedance.
Redox-Dependent Binding to an Electroactive Urea: Comparison of Ferrocene and Phenylenediamine Redox Couples with Two Different Guests
Authors: Logan Kyle , Smith Diane K. 
Published: February 2020

In previous work in our lab, the redox-dependent binding behavior of a phenylenediamine urea, UHH, was investigated in the presence of different guests in CH2Cl2. The urea functionality contains two good H-donors in the two urea NH bonds (a DD motif) that are capable of H-bonding with two appropriately spaced H-acceptors (AA motif). Examples are the cyclic diamide PZD (see Figure) and 1,8-naphthyridine, naph. 1H NMR studies indicated a modest Kbinding of 100 M-1 with PZD and 30 M-1 with naph in CH2Cl2. The expectation was that oxidation of the phenylenediamine couple in UHH to the radical cation would increase the acidity of one of the NH’s leading to stronger H-bonding with the guests and a negative shift in the observed redox potential upon addition of these guests. A small negative shift was observed with PZD, but further research indicated that the actual overall reaction occurring upon oxidation of UHH was not the simple 1 electron oxidation to the radical cation expected, but rather 2 electron oxidation of one UHH accompanied by proton transfer to a reduced UHH to give UH+ and HUHH+ as shown in the Figure. Addition of PZD does not change this overall reaction. An alternative explanation of the potential shift is that PZD is actually H-bonding to the protonated HUHH+, which would also be a stronger H-donor. Interestingly, similar magnitude shifts are observed upon oxidation of the ferrocene-containing urea, FcUHH. Since Fc is only capable of being oxidized by 1 electron, oxidation of the Fc also makes a +1 charge, which appears to have a similar effect on the H-bonding ability of the urea as does protonation.
In contrast to the PZD, addition of naph causes the current for the oxidation of UHH to increase with little change in peak potential. This can be explained by proton transfer from the UHH radical cation to the naphthyridine. The resulting neutral radical will be immediately oxidized by a second electron leading to the increase in current. The proton transfer will change the H-bonding motif from AA-DD to AD-DA, which is inherently weaker because of unfavorable secondary interactions. In addition, because of the two electron oxidation, both binding partners in the resulting complex, (naphH+)(UH+), will be positively charged. Therefore it is not surprising that the H-bonding does not strengthen upon oxidation. It will be of interest to compare this behavior to that of FcUHH and naph. Cyclic voltammetry experiments will be run with FcUHH and naphthyridine to see if eliminating the possibility of the second electron transfer prevents proton transfer and results in the expected stronger H-bonding to the oxidized form.

Figure 1
Flexible and Versatile Nanoparticle Synthesis By Gas-Diffusion Electrocrystallization
Authors: Dominguez-Benetton Xochitl , Prato-Modestino Rafael , Eggermont Sam , Pozo Guillermo , Fransaer Jan 
Published: February 2020

Diverse areas of electrochemistry are greatly impacted by nanoscale materials. In return, electrochemistry is demonstrating a fast-growing impact on their synthesis. This slipstream conveys a vibrant ecosystem for electrochemical breakthroughs that bring about advanced nanomaterials.
Gas-diffusion electrocrystallization (GDEx), a new electrochemical process that we have developed, allows the synthesis of crystalline nanomaterials with well controlled and narrowly distributed properties that relate to specific functionalities. Gas-diffusion electrocrystallization is a one-pot rapid process involving a porous cathode with surface functionalities, an aqueous electrolyte containing metal or metalloid ions, and an oxidant gas, in which colloidal dispersions of nanomaterials or solid nanoparticles are synthesized. The general principles and mechanism through which GDEx operates will be introduced. Furthermore, examples of nanomaterials we have produced and their functionality or industrial relevance will be disclosed.
For instance, cerium oxide nanoparticles with controlled crystallite sizes in the range of 2 to 10 nm as well as varying content of Ce3+ and Ce4+ sites, which result in different degrees of oxygen sorption capacities and kinetics were synthesized using GDEx. Due to this feature, these cerium oxide particles can be tailored for pro-oxidant or anti-oxidant applications of interest for electronic packaging, oxidative stress alleviation, or cancer therapy. Likewise, lanthanum carbonate hydroxides formed by GDEx may find a niche as phosphate scavengers.
GDEx was also used to produce iron oxide nanoparticles in the range of 40 to 100 nm in which the ratio of heamatite (Fe2O3) and magnetite (Fe3O4) can be tweaked, providing the possibility to regulate their magnetic susceptibility. These materials are studied for molecular diagnostics. Solid nanoparticles of herbertsmithite, have been obtained through GDEx when applied to electrolytes containing Cu2+, Zn2+ and Cl– ions, by manipulating the redox potential. These Cu/Zn-based nanoparticles may have applications in data storage, high-temperature superconductors and for so-called ‘‘quantum-entangled’’ batteries.
Finally, when operating GDEx with Mn(III/IV), compositions with birnessite and hausmannite—which may intercalate water and alkali metals— were synthesized, providing promising materials for batteries electrodes or catalysts.
In conclusion, GDEx is revealed as a new route to synthesize a wide range of nanoparticles, flexibly and with versatile control of composition, morphology, and physicochemical parameters such as crystallite size, lattice parameter and particle size, which in turn tailor specific functionalities.

The authors acknowledge the grant from the Flemish SIM MaRes programme for SBO project Get-A-Met.
Energy from Salinity Gradients
Authors: Chittur Krishnaswamy Subramaniam 
Published: February 2020

Osmotic power or salinity
gradient
power (SGP) is the energy available from the difference in the salt concentration between seawater and river water. Two practical methods for this are reverse electrodialysis (RED) and pressure retarded osmosis (PRO). SGP can be generated from reversible mixing of two kinds of water with different salt contents. A process for generating potential from salinity concentration gradient produced in single cell (25 cm2) and multi-cell assembly is presented. The salinity gradient is created using a fuel cell type cell with a micro-porous ion exchange membrane, both anionic (AEM) and cationic (CEM). The study was performed for various gradients. Salt : Fresh, from 100 : 0 to 16000 : 0 was established using NaCl solution, in the electrode chambers. A potential of 25 mV/cm was realized at ambient temperatures and pressures for a bipolar AEM/CEM cell. The achievable potential is still below theoretical value. The performance was optimized for various static and dynamic flow rates of the saline and fresh water. For this purpose the cell flow field was simulated using ANSYS and the flow field design was optimized for maximum coverage of the cell area. The cell performance can further be optimized for various Membrane Electrode System (MES) structure. Cyclic Voltammetry (CV) studies were made to understand the redox process. The electrochemical and electrical efficiency was discussed for various gradients and flow rates. The higher the salinity gradient the larger is the potential generated. This is limited by the membrane characteristics. The membrane characteristics have been studied for optimal ion crossover for various gradients and flow.