bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production of Hydrogen and Chemicals from the Electroreforming of Renewable Alcohols
Authors: Miller Hamish Andrew , Vizza Francesco , Bevilacqua Manuela , Lavacchi Alessandro , Bellini Marco , Chen Yanxin , Wang Lianqin 
Published: February 2020

The exploitation of hydrogen in fuel cells has been widely advocated as the ideal solution for an energetically and environmentally sustainable future for transportation. An essential part of such a solution will be the use of renewable energy resources (photovoltaics, wind, wave power etc.) in conjunction with water electrolysis to provide a “zero emission” source of hydrogen. Water electrolysis is a well-established commercial technology; nevertheless its practical application for the mass production of hydrogen is still limited. Costly electrical energy consumption is certainly one of the major factors hampering the diffusion of electrolysis.
Both Alkaline and PEM electrolyzers exploit water splitting, evolving hydrogen at the cathode and oxygen at the anode. The standard reaction potential for this process is 1.23 V, meaning that water splitting is a strongly uphill reaction. In practice to get current densities in the range of 1 A cm-2 the cell potential usually ranges between 1.6 and 2 V. Considering 1.8 V as a reasonable average, we conclude that 68.3% of the energy input is consumed by thermodynamics, while kinetic factors account for only 31.7%.
Replacing anodic oxygen evolution with the oxidation of much more readily oxidizable species leads to a significant reduction of the potential required to produce hydrogen. Following this strategy compounds such as ammonia, methanol, ethanol, glycerol and urea have been recently tested. These electrolytic processes that lead also to the concomitant generation of chemicals at the anode and hydrogen at the cathode are often indicated as “Electrochemical Reforming”.
While undoubtedly promising, these approaches suffer the limitation of delivering current densities well below 1 A cm-2, and as such are unpractical for technological exploitation.
Here we propose to overcome such limitations using a range of nanostructured anode electrocatalysts which combine fast electrode kinetics for alcohol electrooxidation with tunable selectivity for the formation of partially oxidised intermediates of industrial interest.
We demonstrate that electrochemical reforming can occur at current densities comparable to that of state of the art PEM water electrolysis. Furthermore we report a net energy analysis of hydrogen production by bio-ethanol electrochemical reforming. Particularly, we define the energy cost break-even point, expressed in terms of the Energy Return of the Invested Energy of bio-ethanol production, at which electrochemical reforming becomes more energy efficient than water electrolysis.

Figure.
Electrochemical reforming and water electrolysis comparison. Schematic of (A) PEM water electrolysis and (B) anion exchange membrane electrochemical reforming.

Figure 1
Electropolishing of Nb for Superconducting Radio-Frequency (SRF) Cavities
Authors: Tian Hui , Reece Charlie E 
Published: February 2020

Niobium superconducting radio-frequency (SRF) cavities are widely used in modern particle accelerators, because of higher operating efficiency than normal-conducting cavities made of copper. Since the superconducting RF current flows in a surface layer about 40 nm deep, a set of preparation techniques have been developed over the years to assure good superconducting properties of the surface layer. Electropolishing (EP) is the technique of choice being developed for high–field SRF cavities, which result in a typical surface roughness of about 0.1 μm. Currently, the 1:10 volume ratio HF (49%) and H2SO4 (96%) electrolyte was widely used for high field SRF cavity production. Electrochemical impedance spectroscopy (EIS) and related techniques point to the electropolishing mechanism of Nb in a sulfuric and hydrofluoric acid electrolyte of controlled by a compact surface salt film under F- diffusion-limited mass transport control. In addition, data indicates that above 25oC electrode kinetics become competitive with the mass transfer current limitation and increase dramatically with temperature. These findings are guiding the optimization of EP process parameters for achieving controlled, reproducible and uniform nano-smoothes surface finishing for SRF cavities. The problem with using HF is that it is dangerous both to people and to the environment. Alternative approaches recently were developed, such pulse reverse EP which catholic pulse is used to remove the oxide layer rather than HF, and results are promising. Also ionic solution such as acid-free vitamin B4 electrolyte has been introduced and has shown promising results. Those results will be briefly introduced here.
20 Years of Corrosion Sensing and Microvisualization of Corrosion Processes
Authors: Smyrl William H 
Published: February 2020

Localized corrosion processes continue to be a major cause for degradation failure in damaging fluids. Initiation stages of response remain difficult to characterize, arising in part because of the difficulty in being able to predict the location and onset of the attack. Propagation stages are seldom constant but change with time due to competing processes of dissolution and product deposition at the corrosion sites. The progress of the attack changes the local environmental concentrations which are especially important at buried interfaces that are isolated from bulk conditions. The present paper will describe some of the recent advances in optical, electrochemical, and microscopy that are directed at providing local information on “precursor sites” and vulnerable areas on metal and covering oxide surfaces. Previous studies of coupled reactions on reactive surfaces provide a general basis for the work to be described here.
The objectives of the experimental techniques are: (1) to measure the local corrosion rate; (2) to locate breakdown sites, and; (3) to study the fundamental properties of passive films and how they are related to the stability of the films and damaging environments. The latter is of particular interest since it will allow one to predict why a particular precursor site is more vulnerable to breakdown as compared to neighboring areas.
In locating precursor sites, entire regions of the corroding surface can be imaged concurrently or point-by-point using scanned probe or beam. Both classes will be discussed with their capabilities. The techniques used in our laboratory are: (1) the Quartz Crystal Microbalance (QCM); (2) Optical Fiber Micromirrors (FOP); (3) Confocal Laser Scanning Microscopy (CLSM); (4) Photoelectrochemical Microscopy (PEM); (5) Scanning Electrochemical Microscopy (SECM); (6) Scanning Photoelectrochemical and Electrochemical Microscopy (SPECM); (7) Near Field Scanning Optical and Spectroscopic Microscopy (NSOSM). The experimental setup for each and the capability help to reveal the advantages that are offered by them.
Optical sensing by the QCM and optical fiber micromirrors have been used to measure corrosion rates, with sensitivity of fractions of an atomic layer. Similar to them but with the capability to image a larger reactive surface is the CLSM to determine local attack rates at various surface sites. The NSOSM is valuable to obtain both vertical and lateral super resolution images of reacting surfaces of about 60 nanometers. The techniques support the development of miniature corrosion sensors devoted to monitoring reactive surfaces in remote and occluded regions, coupled with wireless transmission.
Enhanced Surface Finishing of Tungsten Carbide By Using Organic Additives
Authors: Schneider Michael , Schubert Nora , Simunkova Lenka , Michaelis Alexander 
Published: February 2020

The mechanical machining and finishing of cemented carbides is associated with high abrasive wear of cutting tools. Electrochemical Machining (ECM) is the technical application of high rate metal dissolution and well established for steels and several non –ferrous metals. ECM is a priory free of mechanical tool wear. Recently the authors investigated the high rate dissolution of cemented carbides in ammonia containing alkaline electrolytes [1]. The electrolyte system is suitable for ECM of tungsten carbide as well as cobalt. A homogenous dissolution of the compound material was achieved. In industrial practice, Electrochemical Machining is used to realize high surface quality of work pieces. The existence of anodic films during the machining step is important in controlling the texture of the machined surface obtained [2]. If the dissolution process is controlled by material transport through a film of compact dissolution intermediate, precipitated products [3] or viscous product layer [4] the surface will occurs bright and shiny. The formation of viscous surface layers can be enhanced by surface active organic additives of the electrolyte [5]. In the present work the authors investigated the effect of different solvents on the surface roughness during ECM of tungsten carbide. The electrochemical experiments were carried out in a channel flow cell. Firstly, an aqueous solution containing 2M ammonia and 1.5M sodium nitrate was used as reference electrolyte. In a second step ethanol and glycol, respectively, were added. Both additives change the conductivity as well as the viscosity of the electrolyte. All samples were investigated by SEM after the ECM experiments. A decreasing surface roughness in the order of water, water/ethanol and water/glycol was achieved. A quantitative evaluation will be given by using laser scanning microscopy.

References

[1] N. Schubert, M. Schneider, A. Michaelis, Electrochemical Machining of cemented carbides, Int. J. Refractory Metals and Hard Materials 47 (2014) 54-60
[2] J. Bannard, Electrochemical Machining, J. Appl. Electrochem. 7 (1977) 1-29.
[3] T.P. Hoar, T.W. Farthing, Solid Films on Electropolishing Anodes, Nature 169 (1952) 324–325.
[4] P. A. Jacquet, The Electrolytic Polishing of Metallic Surfaces, Metal Finishing Vol. 47 (1949) 83.
[5] J. Bannard, The effect of a surface-active additive on the dissolution efficiency and surface finish in ECM, J. Appl. Electrochem. 7 (1977) 189–195.
(Invited) Thin Films of Eumelanin Pigment: Charge Carrier Transport, Ion Storage, and Interaction with Metal Electrodes
Authors: Kumar Prajwal , Di Mauro Eduardo , Wuensche Julia , Santato Clara 
Published: February 2020

The ubiquitous natural pigment eumelanin is widely studied for its photoprotective, thermoregulating, free-radical scavenging, and anti-oxidant functions in the human body. Recently, eumelanin received increased attention for potential applications in organic bioelectronics due to its unique set of physicochemical properties including strong broad-band UV-Vis absorption, metal chelation properties, and potentially mixed electronic-ionic conduction in a hydrated state [1,2]. To further explore the use of eumelanin in organic bioelectronic devices, the properties of eumelanin thin films interfaced with device components such as metal electrodes need to be investigated in presence of water and ionic species. A good understanding of the interaction of eumelanin with different metal electrodes is also essential to study the intrinsic charge transport properties of eumelanin films, which are still largely undiscovered.
We characterized eumelanin films grown on substrates patterned with gold, platinum, and palladium hydride electrodes using hydration-dependent transient electrical current and atomic force microscopy measurements. We discovered an electrochemical interaction among metal-chelating catechol groups of hydrated eumelanin, Cl- traces in the eumelanin material and Au electrodes, assumed to be electrochemically stable in previously published works on the electrical properties of eumelanin. This interaction leads to the growth of highly conductive Au-eumelanin dendrites between the electrodes, ultimately leading to sudden resistive changes of the sample. This phenomenon suggests new possibilities for biocompatible memory devices and has to be taken into account when integrating eumelanin-like materials in electronic devices [3].
Electrical characterization of eumelanin films interfaced with ion-blocking Pt and proton-transparent electrodes [4] complemented by cyclic voltammetry and impedance spectroscopy measurements give new insights into the charge transport properties of eumelanin films. Our results indicate the presence of protonic currents in eumelanin thin films, increasing with sample hydration, and cannot exclude the presence of electronic currents. These results support recently published data obtained by spectroscopic measurements on eumelanin pellets [2] and underline the attractiveness of eumelanin films for applications at the interface of electronics and biology.
[1] M. D’Ischia et al., Angew. Chem. Int. Edit. 48, 3914 (2009).
[2] A. B. Mostert et al., Proc. Natl. Acad. Sci. 109, 8943 (2012).
[3] J. Wünsche et al., Adv. Funct. Mater. 23, 5569 (2013).
[4] C. Zhong, Y. Deng, A. F. Roudsari, A. Kapetanovic, M. P. Anantram, M. Rolandi, Nat. Commun. 2, 476 (2011).
(Invited) Importance of Interface Engineering in Organic Spintronics
Authors: Jang Hyuk-Jae , Pookpanratana Sujitra , Lee Jun-Sik , Kline R. Joseph , Basham James I. , Gundlach David J. , Hacker Christina A. , Kirillov Oleg A. , Jurchescu Oana D , Richter Curt A. 
Published: February 2020

Organic semiconductors provide a route to revolutionary changes in many areas of device technology with their unique electronic properties and functionalities, which can be easily tailored by chemical synthesis and molecular engineering.[1] In particular, an emerging research area referred to as organic spintronics has initiated a range of device concepts by exploiting spin-related properties in organic semiconductors.[2]
Currently, there are two major interests in organic spintronics technology.[3] One of them is to realize a system enabling the injection/transport/detection of spin polarized charge carriers in organic semiconductors.[3] The other one is to understand and explore the magnetic field effects (MFEs) of organic semiconductors for the development and improvement of organic-based devices such as organic light emitting diodes and magnetic sensors.[3]
It has been known that in organic-based devices, the interfaces between active materials play a critical role in their performance and functionality because the interfaces greatly affect the injection/transport/extraction of charge carriers in organic semiconductors.[4] Recent findings suggest that the interface engineering is also very crucial in organic spintronics technology such as enabling efficient spin-polarized charge carrier injection and tuning of organic MFEs.[5-7]
In this presentation, we will discuss our efforts towards the realization of efficient spin injection and transport in organic semiconductors as well as the modification of organic MFEs by interface engineering. We experimentally show the importance of band alignment between a metal electrode and an organic semiconductor at their interface for efficient spin injection/detection.[6] We will also show how one can utilize a molecular self-assembled monolayer by inserting it between a metal electrode and an organic semiconductor in order to change the characteristics of spin injection into an organic semiconductor from a ferromagnetic metal as well as in order to tune the organic MFEs.[7]

1. Editorial, Nat. Mater.
12, 591 (2013).
2. C. Boehme and J. M. Lupton, Nat. Nano.
8, 612 (2013).
3. W. Wagemans, et al., SPIN, 1, 93 (2011).
4. H. Ma, et al., Adv. Funct. Mater. 20, 1371 (2010).
5. S. Sanvito, Nat. Phys. 6, 562 (2010).
6. H.-J. Jang, et al., Appl. Phys. Lett. 101, 102412 (2012).
7. H.-J. Jang, et al., ACS Nano
8, 7192 (2014).
(Invited) Ionic Liquid-Gated PCBM Transistors: Pushing the Limit of the Doping in Organic Transistors
Authors: Sayago Jonathan , Patel Mitesh , Cicoira Fabio , Soavi Francesca , Santato Clara 
Published: February 2020

Electrolyte-gated (EG) organic transistors are interesting for their low voltage operation and versatile cost-effective fabrication and printability.1 Room temperature ionic liquids (RTILs) are attractive as gating media for their chemico-physical properties, such as ionic conductivity up to 10 mS·cm-1, negligible volatility, and electrochemical stability windows up to ca 5 V.2 The availability of RTILs with different molecular structures gives the possibility to control specifically the interactions between the ions constituting the RTIL and the channel material in view of an optimized doping. Clear guidelines to establish an effective doping as a function of the ions constituting the electrolyte, are yet to be established. In this work we report on EG transistors with phenyl-C61-butyric acid methyl ester (PCBM), as the channel material, and room temperature ionic liquids based on bis(trifluoromethylsulfonyl)imide ([TFSI]) anion, as the gating medium. The cations constituting the ionic liquids were 1-ethyl-3-methylimidazolium ([EMIM]), 1-butyl-3-methylimidazolium ([BMIM]) or 1-butyl-1-methylpyrrolidinium ([PYR14]). Electrical measurements show that the cation strongly affects the behavior of n-type EG PCBM transistors. The higher charge carrier mobility, lower on/off ratio and faster response time obtained with [PYR14][TFSI]-gated transistors, suggests lower cation incorporation into the PCBM channel material. [EMIM][TFSI]- and [BMIM][TFSI]-gated PCBM transistors featured similar electric behavior, coherent with the similar molecular structure of the cations.
1. S. H. Kim et al., Adv.
Mater. Weinheim, 25, 1822–1846 (2013).
2. M. Galiński, A. Lewandowski, and I. Stępniak, Electrochim. Acta, 51, 5567 (2006).
Pvdf Based Gel Polymer Electrolyte for Applications in Flexible Devices
Authors: Oriani Andrea Vittorio , Cojocaru Paula , Spreafico Marco Alberto , Apostolo Marco , Triulzi Francesco , Magagnin Luca 
Published: February 2020

In the last years growing interest is being focused on the production of flexible devices including electronics, organic solar cells and displays. Considering specific applications where electrochemical processes take place, e.g. Die Sensitized Solar Cells (DSSC), an electrolyte is needed between the electrodes to allow ion diffusion and redox reactions. In this case, relevant issues are related to the fluid, namely liquid, nature of traditional electrolytes. Considering this characteristic, the limitation is twofold: on one hand, considering large area devices, for example DSSC integrated in the façade of buildings, electrolyte flow from the top to the bottom of the system can occur. On the other hand electrolyte leakage may occur in the presence of defects or damage, with significant environmental safety concerns. Finally, considering flexible devices, issues are relative to electrolyte flow during bending, due to pressure gradients inside the device. It’s therefore clear that most of these limitations could be overcome using electrolytes with good ion transport properties but also higher resistance to flow with respect to traditional systems, i.e. electrolytes behaving as much as solids when subjected to external loads/strains. For this reason a process is proposed that allows producing a PVdF network by sol-gel method, this is soaked with electrolyte and allows maintaining good ion conductivity and excellent transparency while highly reducing issues related to leakage and electrolyte flow inside between the electrodes of the device.
(Invited) The Effect of Molecular Dynamics on Charge Transport in Organic Semiconductors
Authors: Jurchescu Oana D 
Published: February 2020

Organic semiconductors are studied extensively for their incorporation in next generation large-area, low-weight flexible optoelectronic applications. Librational motion is ubiquitous in such materials; this motion, however, has been difficult to connect with experimental observations of a material’s electronic properties. Here we present the effect of libration on charge transport in monomolecular compounds and binary charge-transfer (CT) complexes through a combined experimental and theoretical approach. The case study of trans-stilbene (STB) and its CTs with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (STB:F4TCNQ) and 7,7,8,8-tetracyanoquinodimethane (STB:TCNQ) will be discussed. It will be shown that the change in amplitude of the torsional oscillation (libration) of the double bond connecting the C7 and C7a carbons in the stilbene molecule results in a crossover from thermally activated to a temperature-independent charge transport. This pedal-like (crankshaft) motion, is responsible for inter-conversion between the two possible conformers. At low temperature the libration amplitude is not sufficiently large to mediate this rotation, generating thermodynamic non-equilibrium states and resulting in freezing in of orientational disorder. The transport can take place only via tunneling, therefore being temperature-independent. At higher temperatures, when inter-conversion motion is fast, a transition to temperature-activated hopping transport occurs.
The following people contributed to this work: K. P. Goetz, A. Fonari, D. Vermeulen, P. Hu, H. Jiang, P. J. Diemer, J. W. Ward, M. E. Payne, C. S. Day, C. Kloc, V. Coropceanu, L.E. McNeil, and O. D. Jurchescu.