bluuebunny/crossref_metadata_2025 huggingface dataset:
Operand AFM Observation of Electrodeposited Lithium Metal
Authors: Sano Hikaru , Kitta Mitsunori , Shikano Masahiro
Published: February 2020

Lithium metal anode is attractive due to its very negative potential and high capacity density, and however, secondary batteries with lithium metal anode are not practically used. One of the biggest obstacle against the wide spread in the market is dendrite formation at the anode during charging.[1] Many researches have been carried out where the mechanism of the dendrite formation of lithium metal were investigated in order to suppress the dendrite formation. Particularly the nano-scale and/or initial behavior of dendrite formation is of importance to elucidate the mechanism. Recently, peakforce-tapping mode AFM (atomic force microscopy) has been commercialized, where the damage to the sample surface from the AFM tip is much smaller than the damage in other conventional mode of AFM.[2] In this study, peakforce-tapping mode AFM was utilized to investigate the initial behavior of lithium electrodeposition in nano-scale in operand.

Lithium wire was cut in the electrolyte and was used as working electrode. Lithium wire was used as a counter electrode, and 0.1 M LiPF6/PC was used as electrolyte solution. Lithium was electrodeposited on working electrode with current density of 2.5 mA cm-2. The working electrode surface was observed by using peakforce-tapping mode AFM in operand. The height and adhesion mapping images were simultaneously obtained.

Two types of protrusions were observed in the series of height mapping images. One type of protrusions increased in size during electrodeposition, while the other type of protrusions kept their size. A series of adhesion mapping images indicate that the former type of protrusions had less adhesive surface than the latter type of protrusions. Furthermore, once the electrodeposition was stopped, the adhesion force of former type of protrusions increases and became the similar adhesion force of latter type of protrusions.[3] In PC solutions, the lithium surface is considered to be coated by surface film. The results may indicate that the surface film on the growing deposits is different from that of static-state deposits. In the case where dendrites had been suppressed, the deposits had been widely and uniformly spread and there had been no contrast at the adhesion images. The AFM technique can be used to detect the dendrite formation even at the very initial state of electrodeposition.

References:

[1] D. Aurbach et al., Solid State Ionics, 148, 405 (2002).

[2] https://www.bruker.com/fileadmin/user_upload/8-PDF-Docs/SurfaceAnalysis/AFM/ApplicationNotes/Introduction_to_Brukers_ScanAsyst_and_PeakForce_Tapping_Atomic_Force_Microscopy_Technology_AFM_AN133.pdf.

[3] M. Kitta and H. Sano, Langmuir, 33, 1861 (2017).

Acknowledgement:

This work was partly supported by the Japan Science and Technology Agency (JST) - Advanced Low Carbon Technology Research and Development Program, “Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING)”.
Surface-Oxidized Titanium Sulfide Nanoparticles As a Conductive Polysulfide Scavenger for a High Performance Lithium-Sulfur Battery
Authors: Jeon Jaebeom , Jung Yeon Sik
Published: February 2020

Theoretically, a solid redox pair of Li and S can be used for energy storage devices with high specific capacity and energy density using low-cost sulfur as the active material, making it one of the most promising candidates to replace conventional lithium ion batteries. However, the practical use of Li-S battery is hindered by persistent issues regarding the formation of soluble polysulfides (PS) during electrochemical cycles and their shuttling effect. In order to minimize the irreversible loss of the active material from the cathode and its subsequent deposition on the anode, a few noteworthy efforts have been reported, including insertion of a protection layer or addition of a functional agent that can adsorb PS on the cathode side.

In this work, we report conductive titanium(III) sulfide (Ti2S3) nanoparticles, synthesized using a simple radio frequency (RF)-powered induction thermal plasma method, as a bifunctional material to be used in the S cathode. Ti2S3 nanoparticles can provide electrical conductivity to the electrode with a smaller volume compared to conventional conducting agent carbon, while simultaneously having PS adsorption adequate to mitigate the diffusion of PS from the cathode and reduce accompanying problems. We prepared Ti2S3 nanoparticles agent with improved PS adsorptivity by applying simple defect chemistry. The synthesized Ti2S3 was first exposed to air to be oxidized and form S defect on its surface. The surface-oxidized Ti2S3 proposed in this work shows both sufficient adsorption property to PS and electronic conductivity, and thus enhance the cyclability and areal energy density of the Li-S battery. The cyclic performance of our Li-S cell was achieved up to ~800 mAh gS
-1 even after 100 cycles at relatively high S loading of 3.0 mgS cm-2.
RuO2/MnO2 Bifunctional Electrocatalysts Supported on CNT with Cathode-Separator monolith for Pragmatic Li-O2 Batteries: High-Rate and High-Areal-Capacity with Improved Cycle Life
Authors: Park Se Hwan
Published: February 2020

Though lithium-oxygen (Li-O2) batteries have very high energy density (about 3.5 kWh kg-1), many obstacles such as low energy efficiency, poor cycle performance and poor rate capability are exist to make Li-O2 batteries widely used. And these problems become severe especially at high areal mass loading. Now, researches were widely done in Li-O2 batteries field but most researches use low areal mass loading cathode. For practical usage of Li-O2 batteries, high areal capacity and mass loading are essential so many researches were unsuitable for commercialization. In this research, air cathode with high areal mass loading was fabricated and this cathode shows unprecedentedly high capacity at high rate along with long cycle life. A separator-carbon nanotube (CNT) monolith-type cathode was fabricated and high areal capacity was achieved, but the high overpotential and poor cycle performance make CNT-only separator monolith cathode unsuitable for pragmatic usage. So we adopted RuO2/MnO2 solid catalysts on the CNT (RMCNT), and sufficient cycle performance, low overpotential and high energy efficiency were obtained. RMCNT have catalytic effects in both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and completely decompose Li2CO3 and LiOH which were byproducts that were made at discharge process and clogged surface of cathode. High mass loading, binder-free, intimate contact with separator, and most importantly, catalysts for reversibility were obtained by this separator-RMCNT monolith. Together, these features provide a remarkably long cycle life at unprecedentedly high capacity and high rate: 315, 45, and 40 cycles, with areal capacity limits of 1.5, 3.0, and 4.5 mAh cm−
2, respectively. At a rate of 1.5 mA cm−
2, Cycling is possible even at the curtailing capacity of 10 mAh cm−
2.
A Nature-Inspired Molecular Catalyst for Sustainable and Efficient Lithium-Oxygen Batteries
Authors: Lee Jun-Seo , Lee Cheolmin , Lee Jae Yun , Ryu Jungki , Ryu Won-Hee
Published: February 2020

Lithium-oxygen (Li-O2) batteries employing a lightweight and gaseous oxygen cathode have been spotlighted because of their exceptional high-energy density (practically 2~3 times higher than lithium-ion cells).[1-2] However, their poor efficiency and cyclability originating from the sluggish kinetics for the formation and decomposition of lithium oxide products (i.e., LiO2, Li2O2) necessitate utilization of efficient catalysts. Although loading of the solid catalysts on the electrode effectively facilitates the Li-O2 cell reactions, they are quickly deactivated upon cycling due to accumulating product residues.[3-4]

Incorporation of soluble redox molecules into an electrolyte has been considered an effective alternative strategy to address the deactivation issues.[5] Their redox properties enable rapid electron transfer from/to the electrode through their self-diffusion and subsequent redox reactions instead of a slow electron movement through the insulating discharge products. Development of potential redox catalysts for Li-O2 cells should meet the following requirements: (i) high mobility in electrolyte; (ii) reversible redox properties for fast electron transfer; (iii) robust stability; and (iv) environmental friendliness.

In this work, we report a class of nature-inspired molecules as an efficient and stable redox catalyst for Li-O2 batteries. Interestingly, the catalyst molecules exhibits catalytic activity for both oxygen evolution and reduction reactions under a certain condition when it forms a stable dispersion of molecular aggregates, which can be controlled by types of electrolyte solvents and exposure to light. As a result of the optimized catalytic activity, the Li-O2 cells facilitated by redox reactions successfully achieve improved efficiency and a longer cycle life compared to reference cells. The reversibility of the Li-O2 reactions in the presence of the molecular catalysts is confirmed by ex-situ characterizations.

[1] Ryu, W. H.; Yoon, T. H.; Song, S. H.; Jeon, S.; Park, Y. J.; Kim, I. D. Nano Lett
2013, 13, 4190-7.

[2] Gittleson, F. S.; Yao, K. P. C.; Kwabi, D. G.; Sayed; Ryu, W.-H.; Shao-Horn, Y.; Taylor, A. D., ChemElectroChem
2015, 2, 1446-1457.

[3] Ryu, W. H.; Gittleson, F. S.; Schwab, M.; Goh, T.; Taylor, A. D., Nano Lett
2015,
15, 434-441

[4] Ryu, W. H.; Gittleson, F. S.; Li, J.; Tong, X.; Taylor, A. D., Nano Lett
2016, 16, 4799-4806

[5] Ryu, W. H.; Gittleson, F. S.; Thomsen, J.; Li, J.; Schwab, M.; Brudvig, G.; Taylor, A. D., Nature Commun., 2016, 7, 12925.
Feasibility of Electrochemical Mg Extraction from MgMn2O4 Cathodes for Mg Rechargeable Batteries
Authors: Hatakeyama Takuya , Shimokawa Kohei , Li Hongyi , Nakao Aiko , Uchimoto Yoshiharu , Ichitsubo Tetsu
Published: February 2020

Mg rechargeable batteries (MRBs) have attracted much attention as a post Li-ion battery owing to high capacity, low electrode potential, and safety of Mg metal anode. However, it is generally a laborious task to seek suitable cathode materials for MRBs. According to the previous report [1], Mg insertion into several kinds of spinel oxide cathodes, Mg(TM)2O4 (TM = Co, Mn, etc), occurs at about 2-3 V vs Mg2+/Mg, which causes the spinel-to-rocksalt transition. In addition, it is noteworthy that Mg extraction from MgMn2O4 has been shown to occur at intermediate temperatures (around 150 ℃), but the detailed mechanism (such as structure change, electrochemical reaction, valence change, etc) has been still unclarified. In this study, we aim to investigate the feasibility of electrochemical extraction of Mg cations from MgMn2O4 to seek a better cathode material delivering a higher voltage.

MgMn2O4 was synthesized by the Pechini method [2] and calcined at 425 °C in air. After mixed with carbon black and binder, MgMn2O4 was coated on Al foil. Electrochemical experiments were conducted in three-electrode cells at 150 ℃, where Li reference electrode was employed to compare with the Li-extraction potential from the same material; the Li reference electrode was well separated from the ionic liquid Mg0.1Cs0.9-TFSA bulk electrolytes with ceramic filters. Compositions and crystal structures of MgMn2O4 cathodes after electrochemical experiments were investigated by ICP, XRD, and XPS analyses.

Compositions of MgMn2O4 cathodes after charge (Mg extraction from spinel) and also discharge (Mg insertion into spinel) processes are shown in Fig. 1. The Mg composition is decreased to 0.73 at charge amount equivalent to 139 mAh/g and to 0.58 at 346 mAh/g from the initial composition (x~1.04), which indicates that Mg cations can be certainly extracted from MgMn2O4, however, accompanying by some degree of electrolyte decomposition. To grasp the electrochemical equilibrium properties of Mg-extraction from MgMn2O4, galvanostatic intermittent titration technique (GITT) was employed. Figure 2 shows that the overpotential of Mg extraction is increased on charging, the open circuit potential reaches 3.9 V vs Li+/Li, and it is substantially unchanged till the end of the measurement. The plateau potential indicates that two-phase equilibrium reaction occurs during the Mg extraction process. Synchrotron XRD measurement reveals that the charged samples consist of the original spinel phase and a cubic spinel phase, and XPS measurement also suggests that the valence state of Mn is shifted to a higher (binding energy) from the initial state after charge.

Figure 1
Phosphorus Decorated Electrospun Carbon Anodes for Highly Efficient Lithium and Sodium Ion Batteries
Authors: Liberale Francesco , Fiore Michele , Ruffo Riccardo , Bernasconi Roberto , Shiratori Seimei , Magagnin Luca
Published: February 2020

Electrospinning has recently attracted considerable attention as a powerful and versatile technique to produce efficient, specifically tailored and high-added value anodes for lithium ion batteries (LIBs) and sodium ion ones (SIBs) [1]. Carbon electrospun nanofibers (CNFs), obtained via polymer electrospinning and subsequent carbonization, provide faster intercalation kinetics with respect to commonly employed powder material thanks to the high surface to volume ratio and to the shorter diffusion paths for ions and electrons transport. They offer a large number of ions insertion sites and the charge-transfer resistance at the electrolyte/active material interface is therefore reduced [2].

Recently, red phosphorus has been considered as one of the most promising anode materials for LIBs and SIBs alternative to the C-based ones [3] but its widespread and easy application has been prevented due to its low conductivity and large volume expansion during cycling, leading to low cyclability and poor rate performances. For this reason, red phosphorus cannot be used alone, but it must be combined with other anode materials able to accommodate its expansion and to increase its conductivity.

Here we suggest a simple double-step procedure to obtain high-capacity electrospun carbon nanofibers anodes and to enhance their electrochemical performances with the insertion of red phosphorus in the matrix. In particular, we propose a simple drop-casting method to confine micro- and nanosized amorphous red P within the carbon mat, thus obtaining an highly efficient, self-standing, binder- and collector-free anode. Red P insertion in the CNFs net has been demonstrated by SEM and TEM analysis and the resulting material has been used to manufacture anodes for LIBs and SIBs. The reversible specific capacity and the rate capability of the obtained composite anodes have been significantly improved with respect to the electrospun carbon mat alone. The outstanding electrochemical performances for both LIBs and SIBs can be accounted to the synergic action of high-capacity red P clusters with the fast transport properties of the carbon fiber mat, acting also as an accommodation-volume matrix for the significant phosphorus expansion during charging/discharging.

[1] Wang, H. G., Yuan, S., Ma, D. L., Zhang, X. B. & Yan, J. M. Electrospun materials for lithium and sodium rechargeable batteries: from structure evolution to electrochemical performance. Energy Environ. Sci. 8, 1660–1681 (2015)

[2] Kim, C. et al. Fabrication of electrospinning‐derived carbon nanofiber webs for the anode material of lithium‐ion secondary batteries. Adv. Funct. Mater. 16, 2393–2397 (2006)

[3] Qian, J., Wu, X., Cao, Y., Ai, X. & Yang, H. High capacity and rate capability of amorphous phosphorus for sodium ion batteries. Angew. Chemie 125, 4731–4734 (2013)
The Micro-Optical Ring Electrode: A Sensor for Multiple Actinide Ions Monitoring
Authors: Linnett Gary , Andrieux Fabrice
Published: February 2020

We present on the development of the Micro-Optical Ring Electrode (MORE) for the analysis of trans-uranium elements in aqueous mixtures. The MORE is a photo-electrochemical device based on a ring microelectrode that uses the insulator interior to the ring as a light guide. This single device exploits the unique photophysical and electrochemical properties of multiple analytes present in mixtures to quantify them. Our study aims to develop a protocol for the analysis of ions of uranium, neptunium and plutonium, which are most relevant to the nuclear industry, especially in the areas of decommissioning and fuel-reprocessing, where speedy and safe identification of radioactive contaminants is essential.

The technique offers a number of advantages over traditional methods in the area of radiochemical analysis such as real time monitoring in-situ, reduced radiation dose impact to the analyst as a result of greatly reduced sample handling and preparation, improved analysis times allowing quick decision making and a much reduced cost (e.g. compared to ICP-MS and Scintillation counting).

Here we present results of our study on successfully generating photocurrents from uranium containing solutions, and describe the response of the sensor as a function of wavelength of illumination, concentration of sensitizer and scavenger species, and include a discussion of limits of detection and interference from additional analytes. The effect of the MORE’s surface finish on photocurrents will also be discussed.
Electrochemistry of SmCl3 and SmF3 in Molten NaCl-KCl
Authors: Stulov Yuriy V. , Kuznetsov Sergey A.
Published: February 2020

Lanthanide elements, which are present in spent fuel from fast nuclear reactors, can be converted into molten salts by anodic dissolution. Electrolysis of molten salts is promising for separation of lanthanides and actinides. To solve this problem, it is necessary to have experimental data on the electrochemical behavior of various lanthanides in molten salts.

The aim of this study is determine the influence of the first coordination sphere composition of samarium complexes on its electrochemistry in molten equimolar mixture NaCl-KCl.

Electrochemical investigations were carried out in a temperature range of 973-1173 K by cyclic voltammetry using an AUTOLAB PGSTAT 20 potentiostat with a package of application programs GPES (version 4.4.). The melt container was a glassy carbon crucible of SU-2000 brand, which also served as an auxiliary electrode. Tungsten wire was used as working electrode and Pt wire was utilized as a quasi-reference electrode.

In the NaCl-KCl-SmCl3 melt it was found that peak current of the recharge process of Sm(III) to Sm(II) is directly proportional to the square root of the polarization rate, while the peak potential does not depend on the polarization rate up to v=0.1 V s-1. According to the theory of linear sweep voltammetry, up to the polarization rate 0.1 V s-1, the electrode process is reversible. However, in the NaCl-KCl-SmF3 molten system the recharge process was reversible up to the scan rate 1.0 V s-1.

Diffusion coefficients of Sm(III) in chloride and chloride-fluoride melts were determined by cyclic voltammetry using the Randels–Sevchik equation.

The quasi-reversible process for the Sm(III)/Sm(II) redox couple was determined in NaCl-KCl-SmCl3 melt at a sweep rate 0.1<v<0.3 V s-1. This mechanism is clearly evidenced by the deviation of the experimental points from linearity in the IC

p vs. v
1/2 plot, by the dependence EC

p on v and by the magnitude of the difference between EA

p and EC

p, which is larger than is required for a reversible process. A transition from a reversible to a quasi–reversible process was found at v > 1.0 V s-1 in the NaCl-KCl-SmF3 melt.

The standard rate constants of charge transfer (k
s) of the Sm(III)/Sm(II) redox couple were determined by cyclic voltammetry both in NaCl-KCl-SmCl3 and NaCl-KCl-SmF3 molten salts using the Nicholson’s equation, which is valid for quasi-reversible processes. The higher values of k
s were obtained in chloride melt than in chloride-fluoride molten system.
Electrochemical Behavior of Niobium Complexes in Chloride-Fluoride Melts with Addition of Alkaline Cations
Authors: Vetrova Daria A. , Popova Anna V. , Kuznetsov Sergey A.
Published: February 2020

The goal of the present research was the study of Mg2+, Ca2+, Sr2+ and Ва2+ (Me2+) strongly polarizing cations influence on the standard rate constants of charge transfer (ks
) for the redox couple Nb(V)/Nb(IV) in NaCl-KCl(equimol.)-K2NbF7 (I) and NaCl-KCl(equimol.)-NaF(10 wt.%)-K2NbF7 (II) melts. Electrochemical studies were carried out in the temperature range of 973-1173 K by cyclic voltammetry. Voltammetric curves were recorded at a glassy carbon electrode vs. a glassy carbon quasi-reference electrode. The sweep rate (v) varied from 0.4 up to 2.0 V s-1. The electrochemical redox process:

Nb(V) + e- ↔ Nb(IV) (1)

was classified as quasi-reversible at a sweep rate ν>0.5 V s-1. The values of k
s were calculated by using the Nicholson’s method [1]. It was shown that k
s increase with increasing temperature. It is due to increase in the number of particles capable of overcoming the potential barrier for the electron transfer process.

Addition of alkaline earth metal cations resulted in increasing of ks
to the certain ratio of Me2+/Nb(V) for the all alkaline earth metal cations due to substitution of Na+ and K+ cations by Me2+ in the second coordination sphere of niobium complexes that leads to decreasing of niobium fluoride complexes strength. Further addition brought to some decrease of the standard rate constants because the viscosity of melts increasing which brings to decrease of the diffusion coefficients.

The temperature dependences of molten salt systems with addition of strongly polarizing cations were determined and the activation energies of charge transfer were calculated. Values of activation energy for systems with strongly polarizing cations are considerably less than activation energies of the initial systems.

The standard rate constants in molten salt system (I) were higher than in the melt (II) due to lower viscosity. It was determined that in the melt (I) ks
a little bit increased with increasing scan rate probably due to the secondary electrode process which accompanied redox process (1). In the system with sodium fluoride (II) the redox process (1) occurs at more negative potentials that allow eliminating the secondary process.

References:

[1] R.S.Nicholson, J. Anal. Chem., 1965. Vol. 37 (1965), 1351.

[2] B.B. Damaskin, O.A.Petriy, Introduction of electrochemical kinetics, Vysshaya Shkola Publ., Moscow, 1975 (in Russian).
Integration of Functional Nanomaterials in Biopolymer Composites Using Ionic Liquid Based Methods
Authors: Trulove Paul C. , Durkin David P. , Fahey Patrick J. , Park Seok , Chung Robert T. , Hoffman Christian E. , ElBidweihy Hatem , Yates Elizabeth A. , Haverhals Luke M. , De Long Hugh C. , Lomax Suzanne Q.
Published: February 2020

Ionic liquids (IL) have been shown to be effective solvents for the dissolution of a wide variety of natural polymers, and new materials can be created from these natural feedstocks by processes that involve their full dissolution and subsequent reconstitution. Yet, the dissolution and reconstitution processes eliminates the native polymer structure often resulting in materials with significantly degraded physical properties when compared to the native material. However, if only the surface layers of these natural materials are mobilized through an ionic liquid facilitated process called Natural Fiber Welding (NFW), the underlying material retains its native character and mechanical properties while still allowing for significant material modification. Furthermore, the addition of functional materials (e.g. magnetic, optical, conductive) into the IL welding solution, allows for these substances to be entrained in and on the surface of the substrate imparting unique properties to the natural materials. In this work metallic nanoparticles were synthesized in linen powders by the process of incipient wetness impregnation. The linen containing nanoparticles were added to an IL and then welded to the surface of a natural polymer substrate (e.g., cotton yarn) via NFW. The morphology of the welded materials and the distribution of nanoparticles was characterized with TEM, SEM, and fluorescent imagery. Raman and infrared spectroscopies were used to evaluate the impact of the nanomaterials on the spectroscopic properties of the biocomposites, and atomic force microscopy and tensile strength testing were used to evaluate the mechanical properties of prepared composites. Using a variety of magnetic measurement techniques, we explored how nanoparticle composition and structure relate to each systems observed magnetic properties, and how some show nanomagnetic behavior at low temperature. Overall, the prepared composites maintained many of the attractive properties of the native substrates, while still exhibiting the functional properties of the entrained materials.
(Physical and Analytical Electrochemistry Division Max Bredig Award Address in Molten Salt and Ionic Liquid Chemistry) From Liquid Clathrates to Ionic Liquids and Back Again. Was Anything Learned on the Journey?
Authors: Rogers Robin Don
Published: February 2020

This address will cover a personal journey through the intersection of the worlds of green chemistry and ionic liquids with insight into the personalities and ideas met along the way. The story starts with roots in undergraduate and graduate research projects on liquid clathrates with Jerry Atwood at The University of Alabama, it grows into research in radiochemistry and separations with Phil Horwitz at Argonne National Laboratory, and it continues to pivot with the reemergence of interest in the IL phenomenon developed in collaboration with Ken Seddon of Queen’s University of Belfast. The constraining or enabling forces of Societal change intersecting with personnel motivation and new insight will provide a backdrop for the lessons learned.
Interaction of 3D Conductive Polymer-Reticulated Vitreous Carbon Composites in Ionic Liquid As Energy Storage Material
Authors: Schoetz Theresa , Ponce de León Carlos , Bund Andreas , Ueda Mikito
Published: February 2020

Energy storage technologies, which combine high specific energy and power with sustainability and low costs, are fundamental drivers for an energy sustainable society. Conductive polymers in highly stable and non-toxic ionic liquid (IL) electrolytes have been proposed as possible systems that combine these advantages. Recently, it has been demonstrated that poly(3,4-ethylenedioxythiophene) (PEDOT) can undergo a redox reaction like in a battery and at the same time perform the characteristics of a capacitor by being doped/charged (de-doped/discharged) by anions from the IL. The storable amount of charges depends on the generated doping/de-doping sites in the polymer, which is a function of the electrode potential. These so called “hybrid-battery-capacitor” system combines the faradaic and capacitive properties in a single electrode [1,2], providing the possibility to improve cell voltages and energy densities.

High surface area materials such as three-dimensional conductive reticulated vitreous carbon (RVC) substrate, provide large surface area for electro-polymerisation of a thin film nano/micro-porous PEDOT active material (“footprint-area” [3]). The resulting composite has large capacitance supported by the rigid carbon substrate which helps to stabilise the typical swelling/contraction process observed in conducting polymers during the electrochemical charge/discharge process.

This study focuses on the synthesis and characterisations of thin electro-active PEDOT films on RVC substrates by electro-polymerisation in IL. The polymer synthesis produced a uniform film on the RVC with a high number of doping/de-doping sites in Lewis neutral 1-ethyl-3-methylimidazolium chloride aluminum chloride (EMImCl-AlCl3) IL with AlCl4
- as doping/de-doping anion.

The interaction of the conductive polymer films with the ionic liquid electrolyte are characterised by combined in-operando atomic force microscopy (AFM) and electrochemical quartz crystal microbalance measurements (EQCM), distinguishing the predominant battery or capacitor behaviour per doping/de-doping site and the correlated changes of the polymer structure as function of the electrode potential.

[1] Chemical Reviews 110 (2010) 4724–4771.

[2] Chemical Society Reviews 44 (2015) 1777–1790.

[3] Advanced Materials 26 (2014) 2440–2445.

Graphical abstract: (A-C) PEDOT electro-polymerised on RVC and (D) schematic illustration of the three-dimensional RVC-PEDOT composite, which is doped (charged) and de-doped (discharged) with AlCl4
- anions of a chloroaluminate ionic liquid.

Figure 1
(Invited) A Fast and Sensitive Detection Method for Detecting CO2 Reduction Products and Local pH
Authors: Zhang Fen , Co Anne C.
Published: February 2020

The electrochemical pathway of CO2 reduction reaction (CO2RR) remains a promising technique to convert CO2 to value-added chemicals (e.g. CO, CH4, HCOOH, CH3OH, etc), which helps alleviate our dependence on fossil fuels as well as mitigate the rising CO2 concentration in the atmosphere. Nowadays, most of the CO2RR study focus on designing novel catalysts to improve their activity and selectivity. However, to evaluate the performance of new catalysts, a long time electrolysis (e.g. 30 min to several hours) is usually required to build up the concentration of products (both gaseous and liquid) enough before product analysis is performed by gas chromatography-mass spectrometry (GCMS) or nuclear magnetic resonance (NMR). This results in a long “pre-concentration-collection-detection” cycle and it greatly limits the efficiency of catalyst screening process as well as increases the energy cost. In addition, for catalysts that degrade quickly with time (within minutes), it is nearly impossible to monitor their product distribution change using traditional detection methods, which directly leads to the product information loss during the study of their degradation mechanisms. Therefore, it is urgent to develop a novel and sensitive detection method that can perform product analysis in a very short time scale (e.g. within minutes).

In this work, we present a systematical study of using RRDE as a fast and reliable detection method for quantifying CO2RR products generated from both heterogeneous (e.g. Pt, Au, Sn) and homogeneous (e.g. [NiII(cyclam)]2+) catalysts. Local pH change during Au and Sn catalyzed CO2RR are also carefully investigated. The fast detection towards single product systems (e.g. H2, CO) and mixture product systems (e.g. H2 and HCOO-, H2 and CO) are discussed in detail. Based on Hori’s classification, catalysis systems of Pt, Au and Sn encompass nearly 90% of the heterogeneous CO2RR reduction products. Our results show that, compared with traditional detection methods (e.g. GCMS, NMR), RRDE shows a superior detection sensitivity (e.g. LOD
ring ~10-18 moles of H2, defined in this work) as well as a significant short detection time (<1 min). Meanwhile, the product distribution as a function of applied electrolysis potential could be easily extracted from the detected ring voltammograms, which provides important information for the evaluation of catalysts’ performance.
Electrochemical Ammonia Synthesis in Molten Salts
Authors: McPherson Ian James , Sudmeier Tim , Fellowes Joshua , Tsang Shik Chi Edman
Published: February 2020

Ammonia is one of the most significant chemical products on the planet due to its central role in agriculture, as well as its use in a wide variety of chemical processes. More recently it has also attracted interest as a carbon-free energy vector, with an energy density similar to that of methanol and immediate compatibility with existing storage and distribution infrastructure. Current ammonia production relies on natural gas for both the hydrogen and the energy required by the high temperature, high pressure Haber-Bosch reaction. This technology consumes over 1% of all global energy and, in Europe, is responsible for 1% of all carbon emissions (1). New processes based on renewable power are therefore urgently required.

Electrochemical reduction of nitrogen to ammonia has been demonstrated in a number of systems, although very slow kinetics and competing reduction of protons to hydrogen has severely limited their efficiency, particularly in protic media (2). One promising approach operates in a molten LiCl-KCl eutectic, the unique electrolyte stabilising the unusual nitride anion and enabling direct reduction of nitrogen gas (3). It has been proposed that this ion can then react with hydrogen or even water at an anode to form ammonia in an electrochemically driven process. Despite promising initial rates and current efficiencies, there has been very little development of the proposed cell, particularly in terms of electrocatalyst composition and morphology.

Here we setup the proposed cell to investigate the feasibility of this approach. We use various methods to deposit metals (Ni, Co, Mo, Fe) onto carbon felt supports to produce a range of different gas electrodes. These electrodes are tested for ammonia synthesis from nitrogen and hydrogen and compared with the rates at a Ni foam electrode used in initial reports.

References

1. Proceedings of the International Fertiliser Society 2008, 639

2. V. Kyriakou, I. Garagounis, E. Vasileiou, A. Vourros, M. Stoukides, Catalysis Today 2017, 286, 2–13.

3. T. Murakami, T. Nishikiori, T. Nohira, Y. Ito, J. Am. Chem. Soc. 2003, 125 (2), 334–335.
Photochemical Nitrogen Fixation on Titania
Authors: Hatzell Marta C. , Liu Yu-Hsuan
Published: February 2020

Photocatalysis is the ideal solution to sustainable ammonia synthesis, as it will enable the distributed production of fertilizers and fuels from reactants that are readily available at ambient conditions: air, water and photons. Given the massive amount of energy currently expended to produce and transport fertilizer, such a process would have an enormous impact on energy consumption and carbon emissions [1,2,3]. Photocatalytic nitrogen reduction has been demonstrated over titania catalysts, although the production rates are too low to be practical. Despite the enormous promise of this reaction, there is little understanding of the fundamental chemical and physical processes that enable it. In this presentation, defects, like oxygen vacancies, and dopants like iron and carbon have been demonstrated to enhance photocatalytic activity for TiO2 for nitrogen fixation. The results indicate that the defects and dopants aid in promoting nitrogen adsorption which consequently may drive photocatalytic performance. Furthermore, insight acquired through ambient pressure XPS and DRIFTs provide new insight into the role this process may play in natural environments.

[1] Medford, Andrew J., and Marta C. Hatzell. "Photon-driven nitrogen fixation: current progress, thermodynamic considerations, and future outlook." ACS Catalysis 7.4 (2017): 2624-2643.

[2]Schrauzer, G. N., Strampach, N., Hui, L. N., Palmer, M. R., & Salehi, J. (1983). Nitrogen photoreduction on desert sands under sterile conditions. Proceedings of the National Academy of Sciences, 80(12), 3873-3876.

[3]Doane, T. A. (2017). The Abiotic Nitrogen Cycle. ACS Earth and Space Chemistry, 1(7), 411-421.
Rational Design of Periodically Ordered Nanoporous Thin-Film Catalysts for Plasmonic Photocatalysis
Authors: Yang Yang
Published: February 2020

Clean chemical fuels generation using heterogeneous photocatalysts is an emerging technology for sustainable energy research. However, the photo-to-hydrogen conversion efficiency of benchmark photocatalysts still appear to be far from practice due to their limited light absorption of solar irradiation spectrum and poor excited carrier lifetime. In this work, novel heterostructured thin-film catalysts with periodically patterned morphology, exhibiting an enhanced light absorption , was developed. Both experimental studies and theoretical modeling demonstrate that the defects in the materials are responsible for the localized surface plasmon resonance (LSPR, visible light absorption) and tunable solar light absorption. The present study will open a new paradigm for direct solar energy harvesting using the rationalized thin-film catalysts.
The Role of Metal Nanostructures in CO2 Photoreduction
Authors: Bienkowski Krzysztof , Kwiatkowska Marta , Solarska Renata Anna
Published: February 2020

Process of CO2 reduction requires substantial decrease of the energy barriers. Consequently, one of the promising way to approach this problem is using use of metal nanoparticles to accelerate electrons and make them more electronegative at the end of this process. Better understanding of the photo-induced phenomena enables to improve design & construction of semiconductor architectures governing the efficiency of CO2 reduction and its selectivity. The objective of this presentation will rely onto use of semiconductor photocathode with co-assembly of plasmonic and catalytic metal nanoparticles, such as silver or gold with other metal electrocatalysts which decrease the energy barriers of the CO2 reduction process through interaction of photo-excited surface plasmon states with adsorbed reaction intermediates. The significance to investigate reduction of CO2 with gold, silver and copper nanoparticles, enhanced by the extra activation of the process provided by the illuminated, incorporated plasmonic metallic nanostructures is supported by the occurrence of the photo-emission process associated with the decay of photo-excited surface plasmons. The occurrence, and contribution of this process to the overall efficiency of the CO2 reduction process as well as its impact on the distribution of the products will be investigated and discussed in detail. Moreover, the tradeoff between CO2 and water reduction will be continuously investigated and discussed in view of choice of the best metal-based catalyst designed for high efficiency and best selectivity CO2 reduction process.
Prompting Mass Transfer in Solid-State Solar Cells Using Submicron Spherical Mesoporous Titanium Oxide Aggregates
Authors: Yang Yuke , Zhang Xiao LI
Published: February 2020

Dye-sensitized solar cells (DSCs) combines benefits of low-cost, simple fabrication and competitive solar energy conversion efficiency. Recent success in the replacement of traditional iodide/tri-iodide redox mediators by noncorrosive, less light absorption cobalt (II/III) polypyridyl complexes has led to encouraging solar energy conversion efficiencies in excess of 13%, well beyond that of iodide/tri-iodide based electrolytes (ca.11%). Solvent evaporation in traditional liquid electrolyte challenges durable encapsulation of DSCs. This has driven increasing focus on alternative semi-solid-state electrolytes for practical DSC applications. Gel electrolytes have exhibited an impressive long-term stability, especially for outdoor applications where temperature of the DSC system can reach 80-85 oC under sunlight. In a solid-state gel electrolyte, the mass transport of cobalt (II/III) complexes is greatly retarded by the highly viscous gelatinous environment, which limits the dye regeneration and thus the overall efficiency of the SS-DSCs. To date, there are still very limited reports of this new type of SS-DSCs, leaving great scope for further development. Sophisticated architectural designs that leverage macro-porosity to promote ionic diffusion and meso-porosity to increase specific surface area for dye loading may also provide a viable solution to tackle the current limit in cobalt gel electrolyte based SS-DSCs, leading to a higher efficiency [1]. In this work, we establish that a simple replacement of photoanode building-blocks from standard commercial TiO2 nanoparticles (CCIC and P25) to titania nanorod aggregates (TNA) enabled remarkable improvement on ionic diffusion of cobalt (II/III) tris(2′2-bipyridine) complexes in a gel electrolyte. An overall solar energy conversion efficiency of over 7.1% and 8.0% was reached by freshly constructed and stabilized SS-DSCs using the TNA, respectively. Those correspond to efficiency enhancements up to 35% and 100% against that of the standard TiO2 nanoparticles – P25 (4.0%) and CCIC (5.9%), respectively.
Ligand Engineered MnO Catalytic Nanoparticles As an Efficient Charge Transfer Mediator for Photoelectrochemical Water Oxidation
Authors: Lee Mi Gyoung , Jang Ho Won
Published: February 2020

Photoelectrochemical (PEC) water splitting is regarded as one of the most promising approaches for the generation of hydrogen as a renewable and carbon-free fuel. Bismuth vanadate (BiVO4) has been recognized a highly promising photoanode material for solar water splitting. However the PEC performance of BiVO4 remains significantly poorer than the theoretical value due to the severe recombination of photogenerated charge carrier near the solid/electrolyte interface. A novel strategy is therefore essential for the progress of highly efficient PEC water splitting. The band edge positions of semiconductors determine their functionality in photoelectrochemical water splitting. While surface modification on the catalytic surface is known to enable to facilitate modification of the band structure, its crucial role in water splitting efficiency has not yet been fully understood.

Here, we firstly demonstrate the ligand engineering effect of manganese oxide Co-catalyst nanoparticles (MnO NPs) on bismuth vanadate (BiVO4)-based cascade anodes, and achieve a remarkably enhanced photocurrent density of 6.25 mA/cm2 at the 1.23 V versus reversible hydrogen electrode. It is the highest value among the previously reported BiVO4-based anodes. We verified that improved photoactivity is closely related to the substantial shifts in band edge energies that originate from both the induced dipole at the ligand/MnO interface and intrinsic dipole of the ligand. In particular, combined spectroscopic analysis and electrochemical study revealed the clear relationship between the surface structure driven by the ligand treatment and the band edge positions of MnO NPs for photoelectrochemical water oxidation. Our systematic study provides general strategy for enabling new active semiconductor photocatalyst and is applicable to solar water splitting system.
Electrochemistry of Particulate Electrodes Based on Magnetite Aggregates
Authors: Accogli Alessandra , Molazemhosseini Alireza , Magagnin Luca
Published: February 2020

In current research, micro and nanoparticulate electrode materials have taken their place because they offer a large internal surface area with respect to the macroscopic dimensions of such electrodes [1]. The nano-impact method is a powerful tool that enables the characterization of individual particulate nano-objects in solution and study of their reactivity [2]. A three electrodes setup system working as a standard electrochemical cell is typically used. Magnetite (Fe3O4) nanoparticles with the strongest saturation magnetization of all naturally occurring iron oxides, combined with properties such as low toxicity, good biocompatibility, high stability, and low production costs, have attracted a lot of interest [3]. There is also substantial interest in their use as magnetic fluids, in data storage, in catalysis, and as electrode materials.

In this work, magnetite micro and nanoparticles have been synthetized by chemical precipitation method in presence of surfactants or functional organic polymer. The use of surfactants to stabilize these synthesized nanoparticles is crucial, as Fe3O4 nanoparticles have high surface energies and tend to aggregate. They also have high chemical activity. Magnetite particles are used as particulate electrode in different fluid and characterized into a three electrodes cell in order to evaluate their electrochemical behavior. A deeper understanding of the particulate electrode has been performed in situ on supported particles through electrochemical AFM/STM measurements, highlighting the behavior of the single aggregate. Together with the charge transfer characterization as a function of particles size and concentration, functionalization and fluid composition, practical applications of the particulate electrodes will be presented. Specifically, the use of particulate electrodes in the production of electrochemical sensors for glucose detection will be discussed.

References

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V Sokolov et al., Phys.Chem.Chem.Phys., 19 (2017) 28

Murugappan, ChemElectroChem, 1 (2014) 1211 – 1218
Ferrocenyl-Based Signal Amplification across Self-Assembled Monolayers in Electrochemical Biosensors
Authors: Mayall Robert Matthew , Renaud-Young Margaret , Luong Samantha , Creager Stephen E , Birss Viola
Published: February 2020

A major challenge in effectively treating infections is to provide timely diagnosis of a bacterial or viral agent. Current cell culture methods require > 24 hours to identify the cause of infection. The Toll-Like Receptor (TLR) family of proteins from the human immune system can rapidly identify classes of pathogens and has been shown to work well in an impedance-based biosensor, where the protein is attached to a Au electrode via a self-assembled monolayer (SAM). While the sensitivity of these sensors has been good, they contain a high resistance (>1 kΩ) SAM, generating relatively small signals and requiring longer data collection times, which is ill-suited to implementation outside of a laboratory.

Here, we describe a refined approach to increasing the signal magnitude and decreasing the measurement time of a TLR-4 biosensor by inserting a redox-active ferrocenyl-terminated alkane thiol into a mixed SAM containing hydroxyl- and carboxyl-terminated alkane thiols. The introduction of ferrocene into the SAM provides an avenue for the electrochemical mediation of soluble redox couples. This dramatically increases the measured current across the SAM when compared to SAMs that do not contain such a redox-active moiety, with confirmation of the intended surface modification of the Au electrodes obtained using a variety of advanced surface techniques.

It is shown that these TLR-4 biosensors, utilizing the ferrocene-based SAMs, exhibit a ≤ 1 kΩ interfacial resistance that can be measured in less than one minute. These biosensors respond selectively to their intended target, Gram-negative bacteria, while remaining insensitive to Gram-positive bacteria or viral particles. These sensors were further interrogated with an inexpensive (< $100) open-source hand-held potentiostat that could be easily employed in a non-laboratory setting, including in remote or third-world applications.

Figure 1