bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Electrochemical Determining and Regenerating Catalytic Materials in Applications of Sensing and Energy
Authors: Huang Jing-Fang
Published: February 2020

Abstract

The growing demand for pure precious metallic catalysts, eq. Pt and Au, and its alloys in applications of sensing and energy makes it necessary to develop facile and efficient processes for regeneration of precious metal containing materials and for characterization of their catalytic and sensing performance. A facile electrochemical characterizing procedure of precious metallic nanoparticles (Ptnano and Aunano) was developed to in situ track the variation in the particle size and density.1-3 In this procedure, the combination of the electrochemically surface area (ECSA) evaluation and the amount of precious metal obtained by the anodic electrolysis (especially for the breakthrough in the electrochemical quantification of Pt content) was used to evaluate the average diameter and the particle density of Ptnano and Aunano on the electrode. This procedure assisted in optimizing analytical parameters of the detection of As3+ in aqueous solution by a Aunano modified glassy carbon electrode and identification of the pathway that mainly contributed to carbon supported Pt catalyst degradation in fuel cell operation.

References

Huang, J. F.; Chen, H. Y. Angew. Chem.-Int. Edit.
51, 1684 (2012).

Huang, J.-F.; Fan, M.-C. J. Mater. Chem.
20, 1431 (2010).

Huang, J. F.; Yang, H. W. Anal
.
Chem
.
64, 6403 (2016).
(Invited) Electrokinetic-Manipulation Integrated Plasmonic-Photonic Hybrid Raman Nanosensors with Dual Enhanced Sensitivity
Authors: Fan Donglei , Liu Chao , Wang Zheng , Li Erwen , Liang Zexi , Chakravarty Swapnajit , Xu Xiaochuan , Wang Alan X. , Chen Ray T.
Published: February 2020

To detect biochemicals with ultra-high sensitivity, efficiency, reproducibility and specificity has been the Holy Grail in the development of nanosensors. In this work, we report an innovative type of photonic-plasmonic hybrid Raman nanosensors integrated with electrokinetic manipulation by rational design, which offers dual mechanisms that enhance the sensitivity for molecule detection directly in solution. For the first time, we integrate large arrays of synthesized plasmonic nanocapsules with densely surface distributed silver (Ag) nanoparticles (NPs) on lithographically patterned photonic crystals via electric-field assembling. With the patterned microelectrodes, the applied electric fields not only assemble the hybrid plasmonic nanocapsules on photonic crystals but also generate electrokinetic flows that focus analyte molecules to the Ag hot spots on the nanocapsules for Surface-enhanced Raman scattering (SERS) detection. The synergistic effects of plasmonic-photonic resonance and the electrokinetic molecular focusing can promote the SERS enhancement factor (EF) robustly to 5×109- 5×1010. Various molecules including SERS probing molecules, nucleobases, and unsafe food additives can be detected directly from suspension. The innovative mechanism, design, and fabrication reported in this work can inspire a new paradigm for achieving high-performance Raman nanosensors, which is pivotal for lab-on-chip disease diagnosis and environmental protection.
(Invited) Non-Volatile Redox Transistors for Low Power Computing and Brain-Machine Interfaces
Authors: Talin Albert Alec
Published: February 2020

The widely anticipated end to Moore’s law and the growing demand for low power computing systems capable of learning, image recognition and real-time analysis of large streams of unstructured data has spurred intense interest in neural algorithms for brain-inspired computing. The brain is capable of massively parallel information processing while consuming only ~1- 100 fJ per synaptic event. Inspired by the efficiency of the brain, CMOS-based neural architectures and tunable resistance elements (memristors) are being developed for low-power pattern recognition and machine learning. However, the volatility, design complexity and high supply voltages for CMOS architectures on one hand, and the stochastic and energy-costly switching of memristors on the other significantly complicate the path to achieve the extreme interconnectivity, information density, and energy efficiency of the brain using either approach. To overcome these limitations, we have recently demonstrated a Li-ion synaptic transistor for analog computation (LISTA).1 LISTA is an all solid-state, non-volatile redox transistor (NVRT) with a resistance switching mechanism based upon the intercalation of Li-ion dopants into a channel of Li1-xCoO2. An NVRT differs from previously described electrochemical transistors in that dopants cannot diffuse out of the channel (after relaxation of applied bias) without an external source of charge to facilitate oxidation and liberate them as ions in a surrounding electrolyte. This is identical to the charge storage mechanism in batteries, which require external current sources to drive charge/discharge redox reactions. A major advantage of the LISTA device is that resistance switching can occur without inducing large structural transformations that are common for memristive devices, such as filament formation or amorphous-to-crystalline phase transformation. In my talk I will show that the structurally stable, diffusion-driven switching mechanism of Li intercalation allows LISTA to operate with a low ‘write’ noise, a near linear response to ‘write’ operations, and orders of magnitude lower switching voltages and currents. Furthermore, our simulations of the device physics demonstrate that scaled LISTA devices will have orders of magnitude lower energy consumption than any resistive memory device to date, and could operate as part of a neural architecture with an energy efficiency matching the brain. Finally, I will introduce an NVRT device based entirely on organic polymers fabricated on flexible substrates. Such devices could in principle form direct interfaces with the brain opening up the opportunity to build advanced neural prostheses with integrated brain-machine interfaces.

1.Fuller, E. J.; Gabaly, F. E.; Léonard, F.; Agarwal, S.; Plimpton, S. J.; Jacobs-Gedrim, R. B.; James, C. D.; Marinella, M. J.; Talin, A. A., Li-Ion Synaptic Transistor for Low Power Analog Computing. Advanced Materials
2016, DOI: 10.1002/adma.201604310
Soft Probe Scanning Electrochemical Microscopy with Spider Array for Visualizing Biomarkers and Redox Active Proteins in Animal Tissues
Authors: Lin Tzu-En , Lu Yu-Jen , Sun Chia-Liang , Chen Jyh-Ping , Lesch Andreas , Girault Hubert H
Published: February 2020

Biopsy is a diagnostic technique for tissue sampling in which a small piece of tissue is taken out from the patient and then sectioned into thin layers. The visualization of specific biomarkers, such as proteins and enzymes, inside the tissue section enables the identification of diseases, especially cancer, and is usually revealed by histochemistry combined with optical detection methods. However, optical methods can often be interfered by the presence of color pigments or auto-fluorescence in the sample.

Locally resolved electrochemical methods, such as scanning electrochemical microscopy (SECM), can detect in an electrolyte solution redox active species whose presence and concentration depend on a direct or enzymatically catalysed reaction at certain biomarkers. Specificity can be achieved by applying immunoassays or other labels, such as functionalized carbonaceous materials.

Standard SECM probes, usually made of metal or carbon micro-disks embedded in hard insulation materials, are of micrometer size and typically used in constant height mode to map the local biomarker concentration as well as distribution. However, tissues are mechanically very sensitive and of impacting topology. Especially topography is difficult to discriminate from the reactivity signal. We developed soft SECM spider probe arrays that brush in a gentle contact mode over tissues and thus enable constant distance mode imaging without inducing damages to the sample. The spider probe contains eight completely individual, parallel microelectrodes to scan square centimeter sized areas on reasonable time scales avoiding sample aging and electrode fouling. We present the successful SECM imaging of certain biomarkers, such as S100 protein and tyrosinase, in thin tumor tissues as well as thick tumor blocks. In addition, we demonstrate the use of the spider array for imaging redox active markers of a complete mouse heart section. This strategy could provide a better understanding of the interaction between redox mediators and redox active centers in animal organs.

References

[1] T.-E. Lin, A. Bondarenko, A. Lesch, H. Pick, F. Cortés‐Salazar, H. H. Girault, Angew. Chem. Int. Ed. 2016, 55, 3813–3816.

[2] A. Lesch, B. Vaske, F. Meiners, D. Momotenko, F. Cortés-Salazar, H. H. Girault, G. Wittstock, Angew. Chem. Int. Ed. 2012, 51, 10413–10416.

[3] T.-E. Lin, A. Lesch, C.-L. Li, H. H. Girault, Mapping the antioxidant activity of apple peels with soft probe scanning electrochemical microscopy, submitted

[4] T.-E. Lin, A. Lesch, H. H. Girault, Spider electrode array for visualizing biomarkers and redox active proteins in animal tissues by using soft probe scanning electrochemical microscopy, in preparation

Figure 1
Using a Semiconductor Detector with Tungsten Collimator for Removal of Tc/Pb Down-Scatter Interference in the Tl/Tc Dual-Isotope Spectrum
Authors: Passmore Gregory
Published: February 2020

SPECT camera imaging of myocardium perfusion is dependent upon maintaining usable geometry between the sodium-iodide (NaI) detector and the view of the patient through the use of an attached lead (Pb) collimator. Both Tl-201 and Tc-99m radiopharmaceuticals can indicate the perfusion characteristics of the myocardium. Of the two, Tl-201 has the capability to differentiate between viable or scarred myocardium. Currently SPECT myocardial imaging protocols require two scans, a resting scan and a post-stress scan. Simultaneous imaging of Tl-201 rest and Tc-99m stress would have the benefits of eliminating potential errors caused by position misalignment between rest/stress scans, significantly reducing study time. In addition, simultaneous Tl-201/Tc-99m would provide optimal perfusion imaging and tissue viability signaling. This would further enhance the diagnostic ability of the modality, especially for those patients contraindicated for other functional imaging such as PET.

However, the standard Pb collimator interacts with the Tc-99m 140 keV photon to create Compton down-scatter components and k-shell x-rays which interfere with imaging the ~70-80 keV Tl-201 photons. This down-scatter reduces image resolution with the resolution poor NaI detector, and obscures Tl-201 defects, falsely indicating viable myocardium. Replacing the Pb collimator with one of differing density and lower energy K-shell x-ray cross-section would potentially reduce the Tc-99m down-scatter photons in the Tl-201 photopeak range by shifting the k-shell x-ray out of the Tl-201 photopeak. Using a semiconductor detector with superior resolution characteristics should allow isolation of both Tl-201 and Tc-99m photopeaks once the scatter components have been eliminated. The aim of the project was to test the ability of a semiconductor detection system with a tungsten (W) collimator in reducing the detrimental effects of Pb generated down-scatter during simultaneous dual-isotope 201Tl/99mTc imaging. Outcomes indicate a significant reduction in down-scatter and increased resolution using semiconductor detection system with W attenuators compared to NaI detection systems with Pb attenuators.
Scalable and Self-Aligned Growth of Two-Dimensional Transition Metal Dichalcogenides Lateral Heterojunctions for Optoelectronic Applications
Authors: Li Ming-Yang , Pu Jiang , Huang Jing-Kai , Miyauchi Yuhei , Matsuda Kazunari , Takenobu Taishi , Li Lain-Jong
Published: February 2020

Recent development in atomically thin layered materials has provided a new possibility for studying two-dimensional (2D) physics. Among them, the monolayer transition metal dichalcogenides (TMDs) with direct bandgaps in the near-infrared to the visible region and with unique electrical and mechanical properties have attracted great research interests and have shown the application potential in optoelectronics. Furthermore, the TMDs heterojunction not only can form the p-n junction as the basic building block for logic circuits, also can provide a new route for band engineering which is of scientific and technology important for exploring next generation electronics. However, the difficulty on precise spatial and geometry control during synthesis or preparation is still an obstacle for 2D materials to integrate into real circuit applications.

Herein, we demonstrate a simple spatially controlled process for synthesizing self-aligned monolayer lateral TMDs heterojunctions array in centimeter scale. The selective growth from metal pad can help on in-situ location and geometry control for forming the heterojunction devices without patterning process. Meanwhile, this etching-free growth method provides a clean and high quality lateral junction. Our WSe2-MoS2 p-n junction exhibits clear current rectification effect and electroluminescence (EL) from the interface under forward bias > 3 V. Detailed EL mechanism shall be discussed. Our self-aligned growth can be easy applied in large scale device fabrication or integrate into circuit design for achieving optoelectronic applications, and also provide a better platform for fundamental studies.
(Invited) Low-Temperature Growth of Transition Metal Dichalcogenides (TMDs) Layered Materials Toward Phase-Engineered Hybrid Films: From Controllable Growth to Material Characterizations and Device Applications
Authors: Chueh Yu-Lun
Published: February 2020

Novel condensed matter systems can be understood as new compositions of elements or old materials in new forms. According to the definition, various new condensed matter systems have been developed or are under development in the recent years. 2D layered materials, including graphene, transition metal dichalcogenides (TMDs) allow the scaling down to atomically thin thicknesses and possess unique physical properties under dimensionality confinement. Chemical vapor deposition (CVD) process is the most popular approach for all kind of 2D materials due to its high yield and quality. Nevertheless, the need for high temperature and the relatively long process time within each cycle hinders for commercial development in terms of production cost. However, the transfer procedure has become one of the major limitations of the overall performance. In the first part of my talk, I will present several approaches, including ultra-fast microwave heating, plasma selective reaction, controlled segregation process by laser irradiation and metal vapers-assisted growth processes developed in my lab these years to directly grow graphene with controllable thicknesses on arbitrary substrates without any extra transfer process. In the 2nd part of my talk, I will also introduce the development of various methods, including laser irradiation assisted-selenization (LIAS) process, fast microwave annealing and plasms enhance selenization processes on different two-dimensional transition metal dichalcogenides materials in my lab. The detailed formation mechanisms, microstructures and physical performances as well as its applications in gas sensors, photodetector and water splitting behaviors based on these two 2D materials were reported and investigated.
In Situ Raman Spectroscopic Studies of Dioxygen Reduction in Ionic Liquid Based Electrolytes for Non-Aqueous Alkali Metal-O2 Batteries
Authors: Radjenovic Petar Martin , Hardwick Laurence J
Published: February 2020

Superoxide (O2
-) is the key discharge intermediary driving many non-aqueous metal-oxygen battery cathode chemistries1–4. Fundamental investigations of the interphase at a roughened Au electrode in a variety of ionic liquid and solvent blended electrolytes have been performed to study electrolyte effects on the chemical nature of O2
- using in situ surface enhanced Raman spectroscopy (SERS). The observed (1095-1165cm-1) and (460-490cm-1) bond vibrations for O2
- at the electrode surface can vary greatly depending on the immediate coordinating environment5–7. Electrolytes that interact weakly with O2
- produce more radical oxide species that may be more likely to undergo parasitic side reactions and degrade alternatively, if stable, O2
- can diffuse away from the surface into the bulk electrolyte enabling a solution reaction pathway that has been linked with higher discharge capacities. Analysis of Raman peak positions, intensities and shifts in oxide spectral bands in different electrolytes and potentials allows for key information on O2
- radical character and its coordination environment to be elucidated. Overall four main parameters were shown to affect the radical character of O2
- at the interface in ionic liquid based electrolytes; (1) surface potential, (2) electrolyte cation, (3) electrolyte anion and (4) solvent electron acceptor/ donor numbers.

Ionic liquids have gained significant attention due to a number of innate physical and electrochemical properties. The significantly large combinations of ions provide the opportunity for electrolytes to be tailored towards specific application, however a clear electrolyte tailoring methodology is remains under developed. Our study provides important information in the oxygen reduction reaction mechanism that can aid in the ionic liquid selection and tailoring process.

References

1. Lu, J. et al.
Nature
529,1–7 (2016).

2. Johnson, L. et al.,
Nat. Chem.
6,1091–1099 (2014).

3. Hartmann, P. et al.,
Nat. Mater.
12,228–32 (2013).

4. Ren, X. & Wu, Y., J. Am. Chem. Soc.
135,2923–2926 (2013).

5. Galloway, T. A. & Hardwick, L. J., J. Phys. Chem. Lett.
7,2119–2124 (2016).

6. Aldous, I. M. & Hardwick, L. J., J. Phys. Chem. Lett.
5,3924–3930 (2014).

7. Aldous, I. M. & Hardwick, L. J., Angew. Chemie Int. Ed.
55, 8254–8257 (2016).

Figure 1
Influence of Electrolyte Additives and Formation Step Protocol on the Cycling Performance of Half and Full Li-Ion Cells
Authors: Sharova Varvara , Moretti Arianna , Diemant Thomas , Varzi Alberto , De Meatza Iratxe , Haon Cédric , Behm Rolf Jürgen , Passerini Stefano
Published: February 2020

One of the key factors, which enables stable performance, cycle life and safety of lithium-ion batteries is the formation of the solid electrolyte interphase (SEI)1. SEI is formed on the surface of the graphite during the first and few initial cycles due to the reduction of the electrolyte components. The formation of this passive layer consumes Li ions, thus leading to the irreversible capacity loss. The control of the SEI formation and growth is complicated as it depends on a number of factors, such as type of graphite, electrolyte composition, cycling conditions and temperature2.

Organic electrolyte composition greatly influences the formation of the passive layer. State-of-the-art electrolytes are usually composed of a combination of cyclic (EC) and linear (DMC, EMC or DEC) carbonates and lithium salt (LiPF6). To provide an SEI with well-balanced physical-chemical characteristics additives are included in the electrolyte formulation. These additives usually decompose prior to the electrolyte main components during the first charge leading to the formation of more compact, stable and ionically conductive passive layer3.

The cell formation protocol also influences the properties of the SEI layer. It has been shown that high current density leads to the formation of porous SEI with high ionic and electronic conductivities, whereas low current density contributes to the formation of denser SEI with decreased electronic and increased ionic conductivities4.

Herein we investigate the influence of the imide-based salts (e.g. LiTFSI, LiFSI and LiFTFSI) as additives on the cyclability of Li-ion cells, comprising graphite and LiFePO4 electrodes with practical loading of ~2.5 mAh cm-2. The electrolytes are investigated focusing on their ionic conductivity and thermal stability. Furthermore, using half- and full-cells, the impact of different formation protocols on the capacity retention and cycling efficiency is evaluated. The SEI formed in different conditions is characterized by electrochemical impedance spectroscopy (EIS) and ex-situ x-ray photoelectron spectroscopy (XPS).

Acknowledgement

The authors kindly acknowledge the financial support from the EU under the H2020 project grant agreement no. 653373 (SPICY – Silicon and polyanionic chemistries and architectures of Li-ion cell for high energy battery).

 

References

1. Peled, E., J. Electrochem. Soc.  126 (12) 1979

2. Verma, P., et al., Electrochim. Acta  55 (22) 2010

3. Kalhoff, J., et al., ChemSusChem  8 (13) 2015

4. An, S. J., et al., Carbon  105 2016
Formation of a Simplified Solid Electrolyte Interphase (SEI) Composed of Lithium Fluoride
Authors: van den Berg Matthijs P , Chidsey Christopher E.D.
Published: February 2020

Direct reduction of lithium hexafluorophosphate (LiPF6) in dimethoxyethane on metallic electrodes yields a pure lithium fluoride (LiF) layer that is passivating to progressive electrolyte reduction, mimicking the beneficial function of an SEI. This layer is shown to be at least as lithium-ion conductive as a similar SEI formed from a commercial electrolyte containing organic carbonates. Electrochemical quartz crystal microbalance results support the stoichiometry of reduction of LiPF6 to soluble elemental phosphorus and insoluble LiF near the expected thermodynamic potential, well above that of common organic electrolyte components. These results suggest that the LiF component of commercial SEI layers may provide the essential functions of passivation and lithium-ion conduction.
Stability of Flow Battery Organic and Organometallic Reactant Molecules
Authors: Goulet Marc-Antoni , Beh Eugene S. , Valle Alvaro W. , Aziz Michael J.
Published: February 2020

Flow batteries for grid scale energy storage have been proposed as a technological solution to the intermittency of renewable energy sources. Aqueous-soluble organic reactant molecules composed of earth abundant elements, such as quinones, show promise for reducing system cost. In addition to low cost, sufficient capacity retention is also a prerequisite for the practical success of any flow battery chemistry. For inorganic systems, capacity retention is often determined by crossover of reactant species, whereas organic reactant crossover is typically lower due to a larger molecular size. Instead of crossover, reactant molecule stability can become the limiting factor for organic flow battery lifetime. In an operating battery, the lifetime of the reactant molecules depends on their chemical stability within the electrolyte as well as on their electrochemical stability during reduction and oxidation. We report here some of the results pertaining to the chemical and electrochemical stability of several organic and organometallic redox reactants in aqueous electrolytes. Chemical stability of molecules is monitored by detection of potential decomposition products by NMR spectroscopy during long duration storage at room temperature and at 60 °C. Electrochemical stability is determined by monitoring oxidation and reduction peak currents during standard three-electrode cyclic voltammetry in addition to capacity measurements in a custom designed two-electrode cell.
Compliant Yet Brittle Mechanical Behavior of Li2s-P2S5 Li-Ion Conducting Solid Electrolyte
Authors: McGrogan Frank P , Swamy Tushar , Bishop Sean R. , Eggleton Erica , Porz Lukas , Chen Xinwei , Chiang Yet-Ming , Van Vliet Krystyn J.
Published: February 2020

Li-ion batteries that include all solid-state components show promise as an emerging energy storage technology, as the solid electrolyte can improve safety and enable longer cycle life than current batteries based on flammable and reactive liquid electrolytes. Mechanical compatibility and durability of the solid components during large intercalation-induced volume changes are key concerns. For example, deformation and fracture of the solid electrolyte during cycling is expected to slow Li-ion conduction and create pathways for dendritic growth of metallic Li that can short-circuit the device. Identification and evaluation of key mechanical parameters of solid electrolytes is critical to predicting designs mitigating mechanical degradation.

With Li conductivity in excess of 10-4 S/cm, 70/30 mol% Li2S-P2S5 (LPS) is among the most promising solid electrolytes to date. Here we fabricated LPS and verified its amorphous structure and high ionic conductivity by X-ray diffraction and electrochemical impedance spectroscopy, respectively. We evaluated mechanical properties including Young’s elastic modulus, hardness, and fracture toughness via instrumented indentation as 18.5 +/- 0.9 GPa, 1.9 +/- 0.2 GPa, and 0.23 +/- 0.04 MPa m1/2, respectively. These measurements were enabled by immersion of the sample in nonreactive fluids that stabilized composition of this moisture-sensitive compound.

We found Young’s modulus to be in agreement with prior published values derived with alternative measurement techniques, and report the first measurements of hardness and fracture toughness. While the stiffness and hardness of this solid electrolyte material were much lower than that of active materials within battery electrodes, the fracture toughness was also surprisingly low relative to typical glass and ceramic materials. Thus, the mechanical behavior of this candidate solid electrolyte is compliant (low resistance to reversible deformation) and brittle (low resistance to fracture). We will discuss the relationship between these observed mechanical properties and integration of these materials as solid electrolytes in all-solid-state batteries.
(Invited) Electrocatalyst Development for Hydrogen and Oxygen Evolution: From Fundamentals to Application in Electrolysis Devices
Authors: Jaramillo Thomas F
Published: February 2020

Catalyst development for hydrogen and oxygen evolution remain significant challenges for the broad commercialization of water electrolysis technologies. This talk will focus on several matters relevant to this technical area. First, a broad overview of electrocatalyst development for both reactions will be presented to establish the fundamental challenges and current opportunities in the field. Next, efforts will be described to obtain high efficiency solar-to-hydrogen (STH) production by coupling high-performance water electrolyzers based on precious metal catalysts with high efficiency photovoltaics (PVs). The remainder of the talk will center on electrocatalyst development for both H2 and O2 production, targeting catalyst with low or zero precious metal content, with investigations ranging from fundamental studies to application in electrolysis devices.
Oxygen and Hydrogen Evolution Activities of IrO2 Nanocrystals Synthesized By Molten-Salt Method
Authors: Mao Yuanbing , Mohan Swati , Ahmed Jahangeer
Published: February 2020

The storage of renewable energy using hydrogen “fuel” has been viewed as a viable mechanism by electrolysis of water into oxygen and hydrogen fuels, but is hampered by the slow kinetics of the oxygen evolution reaction (OER). Hence there is a broad effort to improve performance of currently used materials and develop new materials. Iridium oxide (IrO2) is an effective stable electro-catalyst which can lower the over-potential and keep a remarkable current to improve the efficiency of fuel generation technologies. To further improve its activity with novel nanostructures synthesized by facile and reliable methods, here ultrafine iridium oxide nanocrystals (IrO2 NCs) were successfully synthesized using a facile one-step molten salt synthesis process at 650 oC in air. To tune the size and morphology of these IrO2 NCs, three molar ratios of IrCl4, NaCl, and KCl were employed, specifically 1:10:10, 1:30:30, and 1:60:60. The structural and morphological characterizations of these IrO2 NRs were carried out by powder X-ray diffraction, Raman spectroscopy, Infrared spectroscopy, X-ray photoelectron spectroscopy, and electron microscopic techniques. The electrocatalytic performance of these IrO2 NCs for OER in acidic media was compared with that of commercial IrO2 nanoparticles (NPs) and the annealed derivative in terms of specific capacitance, total charge, most accessible charge, electrochemically active surface area, and roughness factor. The as-synthesized IrO2 NCs show enhanced electrocatalytic OER activity in 0.5 M H2SO4 media compared to the commercial IrO2 NPs before and after annealing. Among all five IrO2 samples, IrO2 NCs synthesized with the ratios of IrCl4:NaCl:KCl = 1:60:60 and 1:30:30 demonstrated better OER activity than commercial IrO2 NPs while the annealed commercial IrO2 NPs showed the worst performance. Moreover, compared to commercial IrO2 NPs and previous reports, the IrO2 nanorods show enhanced electrocatalytic activity to oxygen and hydrogen evolution reactions by passing either N2 or O2 gas in a 0.5 M KOH electrolyte before electrochemical measurements, including cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Our results are comparable with, and in most cases, higher than reported data in the literature. Therefore, the current study reports a novel, reliable and scalable synthetic process from iridium tetrachloride salt for IrO2 nanostructures, but also a type of highly electrocatalytic efficient IrO2 nanostructures. It is expected that these IrO2 NCs can serve as a benchmark in the development of active OER and HER (photo)electrocatalysts for various applications.
Facile Synthesis of Nano-Alloy Particles for the Oxygen Evolution Reaction
Authors: Leonard Daniel Philip , Ji Xiulei , Surta Todd Wesley , Villegas Juan , Mosley Wyatt
Published: February 2020

We report a facile method for the infiltration of late 3d transition metals into nanoporous carbon. This method allows for the deposition of Ni, Fe, and Co, as well as their binary alloys, NiFe, NiCo, and FeCo. Utilizing NH3-saturated water nanodroplets adsorbed within nanoporous carbon, metal precursors are precipitated as metal hydroxides with high dispersion. Following deposition, the MOx-carbon composites are reduced in 5% H2 atmosphere and then alloyed at 1100 °C in Ar. The resulting metal and alloy loaded carbon composites demonstrate excellent activity and stability for the alkaline oxygen evolution reaction (OER). The NiFe, and NiCo alloy composites both require an overpotential less than 400 mV after 2 hours under alkaline OER conditions in saturated O2.
(Invited) Nano-Scaled Perovskites for Oxygen Evolution in Alkaline Environment
Authors: Schmidt Thomas J.
Published: February 2020

Oxygen electrodes are playing a key role in electrochemical energy conversion devices such as fuel cells and water electrolyzers. In both acidic and alkaline environment, both the oxygen reduction and oxygen evolution reaction (ORR and OER), respectively, are limiting the overall energy/voltage efficiency due to its sluggish kinetics. [1, 2]

Whereas in acidic environment, mainly precious metal oxides are used to catalyze the OER (e.g., IrO2), the variety of possible catalysts in alkaline electrolyte is significantly increased and many metal oxide based systems can be employed. Generally the oxygen evolution mechanism is only partly understood independent of the electrolyte environment and material used. In order to help to understand the underlying mechanism for the OER and to support the experimental results, very often computational methods are used, mainly using density functional theory (DFT) calculations. Similar approaches are also used for gaining insights into catalyst stabilities under operational conditions.

In this talk, some of your recent findings on non-noble metal catalysts, mainly from the perovskite family will be presented. By employing operando X-ray absorption spectroscopy (both XANES and EXAFS), important insights could be gained with respect to the perovskite electronic structure and the local catalyst structure helping to better understand the underlying mechanism for the OER.

Acknowledgement:

This work is supported by the Swiss National Science Foundation, the Swiss Competence Center for Energy Research (SCCER) Heat & Electricity Storage, the Swiss Federal Office of Energy and the Competence Center Energy & Mobility Switzerland.

 References

[1] A. Rabis, P. Rodriguez, T.J. Schmidt, ACS Catal., 2012, 2 (5), 864–890

[2] E. Fabbri, A. Habereder, K. Waltar, R. Kötz, T.J. Schmidt, Cat. Sci. Tech., 2014, 4, 3800-3821
(Invited) Integrated Metal Oxide Hybrid Perovskite Photoelectrode for Efficient Photoelectrochemical Water Splitting
Authors: Roy Subhasis , Botte Gerardine G
Published: February 2020

In these present days where developing unconventional sources of energy is a major concern, sunlight-driven water splitting has attracted much attention due to sustainable hydrogen fuel production as a substitute of conventional energy. Although sunlight-driven water splitting is an eco-friendly and interminable energy source, extensive implementation is hindered by the expense of the essential photo anode.1-2

In this contribution, we demonstrate an efficient and low-cost water-splitting cell by combining a charge carrier metal oxide semiconductor - processed multidimensional perovskite thin films photoanodes. Effort has been made to prepare nanostructured morphologies of metal oxide as well as perovskite photoanodes that possesses optimized surface catalytic reactions; as well as high photocurrent by controlling the morphology of the structure.3-4This nanostructure material capable to overcome the shortcoming of the short hole diffusion length and enhancing photocurrent. The spectral absorbance of the materials have been also fine-tuned by controlling dimensionality of the structures as well as through doping. We optimized the necessary parameters for high performance photo electrochemical water splitting, by balancing photon absorption and charge carrier transport. A significant improvement in the state-of-the-art perovskite photo anodes through an enhancement in electron transport in films attained and these porous photoanodes films could be easily modified by metal doping for further enhanced photo electrochemical activity for solar water splitting.

This hybrid “modify perovskite nanostructures” composites is different from existing composites in that they (i) are produced using benign solvents and processing techniques, and (ii) possible to modify to introduce virtually any desired functionality tailored to the desired application. Our materials are much simpler to prepare and can easily be modified with virtually any desired functionality to optimize performance in different applications. Specific properties can also be dialled in by choosing the appropriate linking molecule (rigidity/flexibility, stimulus responsiveness, etc.). The flexibility of this approach leads to practically unlimited possibilities, while the technology is based on the most abundantly available in nature.

 References

Y. Kuang, Q. Jia, H. Nishiyama,T. Yamada, A. Kudo, K. Domen, Advanced Energy Materials, 2016, 6, 1501645-51. 

A. Kudo, K. Omori, H. Kato, Journal of the American Chemical Society
, 1999, 121 11459-67. 

K. Sayama , A. Nomura , Z. Zou , R. Abe , Y. Abe , H. Arakawa , H. Arakawa , Chemical Communications,
2003 , 39 , 2908-2909. 

K. Kim, P. Thiyagarajan, H.-J. Ahn, S.-I. Kim and J.-H. Jang, Nanoscale, 2013, 5, 6254–6260
A PEC Hydrogen Evolution Reaction with Quantum Yield Exceeding 100% via MEG
Authors: Yan Yong , Beard Matthew C
Published: February 2020

Multiple exciton generation (MEG) has been shown for quantum dots (QDs) in solution and in quantum dot solar cells. Direct conversion of solar energy to chemical fuels can also benefit from the enhanced conversion efficiency afforded by MEG. We present here a lead sulfide (PbS) QD photoelectrochemical cell that is able to drive a hydrogen evolution reaction with a peak external quantum efficiency (EQE) of over 100%, with the highest EQE at 114±1.3%. QD photoelectrodes with bandgap energies (Eg) of 0.85, 0.92 and 1.08 eV all demonstrated clear MEG where absorption of a photon with at least 2.7xEg begins to produce more than one electron-hole pair per absorbed photon. Our results show that the extra carriers produced via MEG can be used to drive a chemical reaction with above unity quantum efficiency thus demonstrating a new direction in exploring high efficiency approaches for solar fuels.
Hierarchical NiCo2O4 Micro-/Nanostructures with Tunable Morphologies As Anode Materials for Li-Ion and Na-Ion Batteries
Authors: Chan Wai Leong Mickey , Fu Fang , Li Jiadong , Yao Yuze , Shao Minhua
Published: February 2020

Binary metal oxide NiCo2O4 is a promising anode material for future Li-ion batteries (LIBs) and Na-ion batteries (SIBs) owing to its inherited characteristics of high theoretical capacity and low cost.1,2 In particular, NiCo2O4 possesses high electrical conductivity, reversible capacity and mechanical stability than single-component metal oxides NiO and Co3O4.
3,4 However, the large volume change and sluggish kinetics during the charge/discharge process result in a short cycling life and poor rate performance, which limits its practical application.5

The electrochemical performance of an active material highly depends on its structure (both primary and secondary structures).6 Therefore, tailored architecture design and surface engineering of NiCo2O4 are highly desirable to secure both the high transport kinetics and sustain the structure integrity for high rate and long life.

In this study, one-dimensional (1D) porous NiCo2O4 microrods and microspheres are successfully synthesized by a simple solvothermal method using different solvents followed by calcination. The solvothermal process and solvents employed in the synthesis play crucial role in determining the final morphologies of NiCo2O4. Compared with NiCo2O4 microspheres, the porous microrods exhibit much better Li- and Na-ion storage properties owing to the 1D geometry to facilitate fast ion transport and the porous structure to accommodate volume expansion of NiCo2O4 during ion insertion. The porous NiCo2O4 microrods display high initial charge capacity (1046.1 mAh g-1 at 100 mA g-1), long cycling stability (719 mAh g-1 after 600 cycles at 500 mA g-1), and rate capability for lithium-ion batteries. They also show better performance in sodium-ion batteries. This work may provide a facile way for fabricating novel structured metal oxide anode materials for batteries.

Figure 1. (Left) SEM images of the 1D porous NiCo2O4 microrods and microspheres for LIBs and SIBs respectively. (Right) Rate performances at various current densities of LIBs and SIBs.

References

Zheng, F. C.; Zhu, D. Q.; Chen, Q. W. ACS Applied Materials & Interfaces
2014, 6, (12), 9256-9264.

Lee, Y.; Kim, M. G.; Cho, J. Nano letters
2008, 8, (3), 957-961.

Li, B.; Feng, J.; Qian, Y.; Xiong, S. Journal of Materials Chemistry A
2015, 3, (19), 10336-10344.

Jadhav, H. S.; Kalubarme, R. S.; Park, C. N.; Kim, J.; Park, C. J. Nanoscale
2014, 6, (17), 10071-10076.

Chen, J.; Ru, Q.; Mo, Y.; Hu, S. RSC Advances
2015, 5, (90), 73783-73792.

Ye, J.; Liu, W.; Cai, J.; Chen, S.; Zhao, X.; Zhou, H.; Qi, L. Journal of the American Chemical Society
2010, 133, (4), 933-940.

Figure 1
Correlation of Photocatalytic Activity with Band Structure of Perovskite Lanthanum Titanium Oxide
Authors: Wu Nianqiang (Nick)
Published: February 2020

This talk deals with the relationship between the photocatalytic activity and the band structure of perovskite lanthanum titanium oxide (La2Ti2O7). Nitrogen doping results in shift of the valence band, leading to band gap narrowing. This renders the visible-light responsive photocatalytic activity of lanthanum titanium oxide. Transient absorption spectroscopy has been used to investigate the charge dynamics in both the pristine and the N-doped perovskite lanthanum titanium oxide.
Tuning Electrocatalytic Activity of Ultrathin Pd Shells: CO2 to Fuels
Authors: Fermin David , Humphrey Jo , Celorrio Veronica
Published: February 2020

It is well established that thin metal layers on a foreign support can exhibit very distinctive electrocatalytic activity with respect to bulk electrodes. In the case of d­-metals, changes in reactivity can be rationalised in terms of the so-called ligand or strain (also known as geometric) effects. Although is commoly argued that ligand effects are rather short range (sub-monolayer to few atomic layers), it is notoriusly difficult to experimentally differentiate the contributions from these two phenomena. In this contribution, we shall explore ligand and strain effects on the electrocatalytic properties of Au-Pd core-shell nanoparticles towards CO2 reduction to fuels. The electrochemical properties and product generation are probed by off-line 1H NMR, differential electrochemical mass spectrometry (DEMS), on-line Mass spectrometry (OLEMS) and in-situ FTIR.

Thin Pd shells were grown onto 20 nm Au nanoparticles employing a colloidal synthesis method at low temperatures, generating continuous shells with tuneable mean thickness between 1.3±0.1 (CS1) and 9.9±1.1 nm (CS10). Selected area electron diffraction patterns revealed that the effective Pd strain decreases from 3.5 to less than 1% in this thickness range, which is consistent with strain relaxtion mechanisms at Au {111} surfaces. DEMS was used to calculate the faradaic efficiency associated with the CO2 reduction vs hydrogen evolution at the core-shell nanostructures supported on a porous carbon layer. The data show that over 90% of the faradaic charge in the range between 0.0 to -0.5 V vs RHE is consumed in CO2 conversion at CS1 nanoparticles, as opposed to approximately 40% in the case of CS10. The analysis of the electrolyte solution employing 1H NMR revealed the formation of HCOO- only in the case of CS10 over a narrow potential range centred at -0.4 V, with faradaic efficiencies close to 30%. Furthermore, CH4 and C2H6 were also detected using OLEMS at potentials as negative as -0.7 V at the CS10 nanoparticles. No products in solution were detected In the case of CS1, indicating that CO is the main product generated over the entire potential range.

The contrast in reaction pathway and electrocatalytic performance are rationalised in terms of the CO affinity to the Pd nanoshells. To probe this, in-situ FTIR studies were performed revealing that the potential dependence of the adsorbed C-O stretching band (stark slope) is significantly weaker on CS1 in comparison to CS10. Furthermore, the effective CO coverage increases with increasing Pd thickness, reaching values reported for polycrystalline bulk Pd electrodes in the case of CS10. These results show that CO has a significantly weaker binding to strain Pd shells (CS1). Finally DFT calculations are used to estimate the contributions of the so-called ligand and strain effects on the local density of states of the Pd d-band. The calculations strongly suggest that the key parameters contributing to the change in mechanism is the effective lattice strain.
Electrochemical Properties and Reactions of Organoboron Compounds
Authors: Suzuki Junji , Tanigawa Masahiro , Kuriyama Yu , Ohtsuka Kazuhiro , Shida Naoki , Inagi Shinsuke , Fuchigami Toshio
Published: February 2020

Organoboron compounds are highly useful in various fields such as synthetic organic chemistry, pharmaceutical chemistry, and materials chemistry as well as analytical chemistry. However, there have been limited reports dealing with their electrochemical properties and reactions to date.1-3) Quite recently, we found marked negative shifts of the oxidation potentials of alkyl and aryboronic acids and their esters in the presence of fluoride ions compared with those in the absence of fluoride ions. 4-8) It was also clarified that negative shift was derived from the formation of negatively charged boron-ate complex with fluoride ions. In this talk, we focus on our new finding of the β-effect of organoboronic acid esters having a heteroatom or unsaturated bond at their α-position, which is more pronounced compared with that of the corresponding organosilicon compounds. 5,6,8) Anodic radical coupling of organotrifluoroborates7) and substitutions of organoboronic acid esters with oxygen nucleophiles have been achieved. 4-8) Thus, we have shown that boryl groups work as electroauxiliaries like silyl groups.

References:

1) J. Yoshida, T. Nokami, and S. Suga, in Organic Electrochemistry, 5th Ed., O. Hammerich and B. Speiser (Eds.), CRC Press, FL, (2015), Ch. 35

2) H. Scha¨fer and D. Koch, Angew. Chem. Int. Ed.
11, 48 (1972).

3) L. A. Shundrin, V. V. Bardin, H.-J. Frohn, Z. Anorg. Allg. Chem. 630, 1253 (2004).

4) J. Suzuki, N. Shida, S. Inagi, and T. Fuchigami, Electroanalysis, 28, 2797 (2016).

5) M. Tanigawa, Y. Kuriyama, S. Inagi, and T. Fuchigami, Elecrochim. Acta, 199, 314 (2016).

6) K. Ohtsuka, S. Inagi, and T. Fuchigami, ChemElectroChem, in press, DOI:10.1002/celc.201600519.

7) J. Suzuki, M. Tanigawa, S. Inagi, and T. Fuchigami, ChemElectroChem, in press, DOI: 10.1002/celc.201600451.

8) K. Ohtsuka, S. Inagi, and T. Fuchigami, J. Electrochem. Soc. in press, DOI: 10.1149/2.0561702jes.
Magnetite Nanospheres As Modifier of Carbon Paste Electrode for Determination of Inhibition Kinetics of Syzygiumpolyanthum extract Toward Xanthine Oxidase
Authors: Saprudin Deden , Ernis Gustria , Darusman Latifah K
Published: February 2020

Magnetite nanospheres was prepared and used to fabricate a modified carbon paste electrode as xanthine biosensor and applied to determine inhibition kinetics of Syzygium polyanthum extract toward xanthine oxidase (XO). The magnetite nanospheres was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical behavior of xanthine was investigated by immobilizing the XO on the surface of carbon paste electrode (CPE), modified magnetite nanospheres-CPE (MCPE), and modified 2,3-dimethoxy-5-metil-1,4-benzoquinone (Q0)-CPE (QCPE) employing cyclic voltammetry (CV) technique. The result showed that the MCPE was the best electrode to determine the analytical performance under optimum condition, based on lower limit of detection (0.005 mM), wider linearity range (0.01-1 mM with R2= 99.24%), and higher sensitivity (5.16 µM-1) than the two oter electrodes (CPE and QCPE). The MCPE successfully improve the analytical performance on xanthine biosensor and to be applied for determining inhibition kinetics of S. polyanthum extract. Inhibition kinetics of the extract has caused increase of KM and VMAX (IMAX) constant. Based on the result, the type of inhibition kinetics was a competitive inhibition.
Direct EPR Evidence of Cathodic ECL Coreactant Intermediates of Benzoyl Peroxide and Ammonium Persulfate
Authors: Bastola Pradip , Miao Wujian
Published: February 2020

Electrogenerated chemiluminescence (ECL) coreactants are crucial towards their roles in forming radical intermediates for chemical oxidation or reduction of the ECL emitters, such as rubrene (RUB) or 9,10-diphenylanthracene (DPA), to form excited state species that emit light. During the cathodic potential scanning, ECL coreactants such as benzoyl peroxide (BPO) and ammonium persulfate were believed to generate benzyloxy free radical (C6H5CO2
• or BPO•) and sulfate anion radical (SO4
-•), respectively, resulting in the chemical oxidation of the ECL emitter and eventually the ECL production. The direct electron paramagnetic resonance (EPR) evidence of the above radical intermediates, generated via chemical reduction of the ECL coreactant benzoyl peroxide in MeCN and ammonium persulfate in water using hydrazine as the reducing agent and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin trapping agent, was obtained. Additionally, EPR spectra of C6H5CO2
• (without DMPO trapping) generated from solid state using UV irradiation were consistent with the spectra obtained from solution phase. The EPR spectra of SO4
-•(with DMPO trapping) were also obtained. Simulations of the experimentally acquired EPR spectra were conducted with EPR simulating software, such as PEST winsim.

Financial support from the NSF CAREER Award (CHE-0955878) is gratefully acknowledged.