bluuebunny/crossref_metadata_2025 huggingface dataset:
Crack Behavior of Secondary Particles in Li-Ion Battery Electrodes during Lithiation/De-Lithiation Cycles
Authors: Zhang Yuwei , Guo Zhansheng
Published: February 2020

The loss of connectivity in particle-based LiMO2 (M = Ni, Co, Al, and/or Mn) electrodes due to mechanical failure and fracture at the interface between primary particles is one of the major causes of capacity fading in Li-ion batteries (LIBs) after certain electrochemical cycles. In this study, a model of a secondary particle composed of randomly distributed primary particles is established using a fractal algorithm. The finite element method with cohesive crack modeling is employed to simulate the intraparticle fracture within the secondary particle. The different fracture energies are analyzed during the lithiation process and the crack behavior during the lithiation/de-lithiation cycling is studied. The fracture energy has a significant influence on the crack density and crack branching. Model I cracks appear at the center of the secondary particle during the lithiation process along with the crack branching phenomenon. A model II crack appears on the surface of the secondary particle during the lithiation process. The damage during the electrochemical (lithiation/de-lithiation) cycling results in cracks within the secondary particle, which can penetrate the entire particle after certain lithiation/de-lithiation cycles.
Symmetric and Asymmetric Capacitive Deionization Cells Using Modified Porous Carbon Electrodes
Authors: Gao Xin , Omosebi Ayokunle , Landon James , Ma Zilong , Ghorbanian Mahyar , Kern Neil , Liu Kunlei
Published: February 2020

Capacitive deionization (CDI) is an emerging approach to water treatment that makes use of common porous carbon materials to electrostatically remove ions from a solution.(1-3) Desalination using CDI is achieved in a flow cell consisted of a minimum of a pair of porous carbon electrodes separated by a water channel as sketched in Fig. 1(a). Often, constant-voltage operation is adopted to investigate ion transport of a CDI cell with a charging voltage (V
ch) for ion adsorption and a discharge voltage (V
dis) for ion desorption.(2)Details are illustrated in Fig. 1(b) by using an ionic charge curve plotted in a potential distribution diagram, where the ionic charge curve is defined by the modified Donnan (mD) model with chemical surface charge for a single carbon electrode according to reference (4, 5).

Ion adsorption-desorption by a CDI cell depends upon the placement of the potential of zero charge (E
PZC) versusE
oin a potential distribution diagram,(6)where E
PZC commonly defines a potential when the electrode has a minimum in ion adsorption,(7)as depicted at the lowest point on the ionic charge curves in Fig. 1(b). In this work, by modifying carbon surface chemistry using carbon oxidation, scenarios of different E
PZCversus E
o are created to investigate the effect of carbon surface charge on ion adsorption-desorption of a CDI cell. A comprehensive study will be performed to demonstrate the importance of the E
PZCparameter in a potential distribution diagram on resulting adsorption-desorption characteristics, primarily including real-time measurements of the potential drops at the CDI electrodes during charging and discharging, and developments of a new approach to estimate the E
PZCaccording to the mD model with chemical surface charge.

References

J. Landon, X. Gao, B. Kulengowski, J. K. Neathery and K. Liu, J. Electrochem. Soc., 159, A1861 (2012).

X. Gao, J. Landon, J. K. Neathery and K. Liu, J. Electrochem.Soc., 160, E106 (2013).

A. Omosebi, X. Gao, J. Landon and K. Liu, ACS Appl. Mater. Interf., 6, 12640 (2014).

X. Gao, A. Omosebi, J. Landon and K. Liu, J. Phys. Chem. C, 122, 1158 (2018).

P. M. Biesheuvel, H. Hamelers and M. Suss, Colloids Interf. Sci. Commun., 9, 1 (2015).

E. Avraham, M. Noked, I. Cohen, A. Soffer and D. Aurbach, J. Electrochem. Soc., 158, P168 (2011).

A. J. Bard and L. R. Faulkner, Electrochemical Methods - Fundamentals and Applications, John Wiley & Sons, New York (2001).

Acknowledgement

This work is supported by the Crosscutting Research, National Energy Technology Laboratory, U.S. Department of Energy (DE-FE0031555).

Figure 1
Metal Nanowire Felt As a Flow-through Electrode for High-Throughput Electrosynthesis
Authors: Wiley Benjamin J. , Kim Myung Jun
Published: February 2020

The low productivity of organic electrosynthesis limits the adoption of this green methodology for production of organic chemicals. This work examines to what extent reducing the size of the fibers in a flow-through electrode to the nanoscale can increase the productivity of electrosynthesis. A Cu nanowire felt, made from nanowires 45 times smaller than the 10-mm-wide fibers in carbon paper, achieved a productivity 278 times higher than carbon paper for mass transport-limited reduction of Cu ions. For an intramolecular cyclization reaction that was limited by both mass and charge transfer kinetics, the Cu nanowire felt achieved a productivity 4.2 times higher than carbon paper. This work demonstrates large gains in productivity can be achieved with nanostructured flow-through electrodes, but that potential gains can be limited by charge transfer kinetics.

Figure 1
Conformal Coating on Inverse Opaline Scaffolds for Enhanced Mechanical Properties and Thermal Stability
Authors: Hung Pei-Sung , Chou Shih-Cheng , Wang Guang-Ren , Wang Chuan-Jyun , Chung Wei-An , Wu Pu-Wei
Published: February 2020

The ordered arrangement of meso/macropores in the inverse opaline structure could be beneficial to enhance the performance for several applications, such as sensing, electrocatalysis and filtration. One of the critical concerns for its practical use could be regarded to the mechanical properties of this structured material. We had successfully demonstrated the fabrication of larger-area Nickel inverse opaline films through a facile electrochemical route. In this work, a pulse voltage electrophoretic deposition or CV electro-polymerization was subsequently applied to a metallic inverse opaline film as working electrode. Several experimental parameters, including the recipes for deposition bath and the pulse programs, were explored and studied. With optimized experimental parameters, a conformal coating of oxide or polymeric materials on the skeleton of inverse opals could be successfully achieved. Their mechanical properties were evaluated by nanoindentation and microtensile test. Other structural and compositional characterization were conducted by SEM, EDS, XRD, and XPS analysis.
Luminescence and Magnetic Properties of Porous Silicon Investigated with Respect to Its Metal Filling
Authors: Granitzer Petra , Rumpf Klemens , Poelt Peter , Reissner Michael
Published: February 2020

The influence of magnetic metal filling on the optical and on the magnetic properties of luminescent porous silicon (PSi) is presented. The metal deposits affect, depending on their amount, the optical behavior but also give rise to specific magnetic properties. Due to the metal filling of the porous silicon the photoluminescence is blue-shifted and furthermore an increase of its intensity is observed. The modification of the optical properties, especially of the photoluminescence and its life time and the magnetic characterization of the nanocomposits is elucidated. First the optical properties of the luminescent PSi are investigated, second Ni is deposited electrochemically within the porous silicon samples and subsequently the nanocomposite specimens are characterized optically again and also magnetically. The samples are structurally characterized by SEM, EDX and TEM.

Photoluminescence spectra of bare PSi show a maximum around 620 nm whereas in the case of Ni filled samples the peak is blue-shifted to around 580 nm and the luminescence intensity is increased. The observed blue shift of the photoluminescence peak with increasing metal deposition time and the enhancement of the photoluminescence intensity as well as a decrease of the photoluminescence life time can be interpreted by a decrease in the radiative life time. The enhancement of the photoluminescence intensity is interpreted by the coupling of the silicon emitter to the Ni plasmons. Due to the direct vicinity of the emitter and the metal structure, only separated by a thin SiO2 native layer, coupling of the plasmonic modes with the emitter can occur [1].

Concerning the magnetic properties of the nanocomposite the embedded Ni structures can be superparamagnetic from the size of the pore diameters but due to the branched morphology the achieved deposits tend to be interconnected and thus do not offer necessarily a superparamagnetic behavior [2]. Also temperature dependent magnetization measurements give no hint for superparamagnetism. Field dependent magnetization measurements performed with the magnetic field applied perpendicular and parallel to the sample surface show a high magnetic anisotropy. It can be clearly seen that the samples offer a film-like behavior due to the interconnected Ni structures which is represented by the easy axis parallel to the surface. The magnetic properties of the Ni filled PSi also offer a dependence on the amount of deposited metal. An increase of the deposition time meaning an increase of the metal amount within the porous layer leads to more interconnected metal structures. This behavior is evidenced by the enhancement of the coercivity and the magnetic anisotropy.

The presented systems are promising candidates for applications in optoelectronics and also for magneto optical integrated devices.

[1] A. Huck, U.L. Anderson, Nanophotonics (2016), 5, 1.

[2] G. Bertotti, Hysteresis in Magnetism, 1st Edition, Academic Press, 1998.
(Invited) Superconformal Electrodeposition
Authors: Moffat Thomas P. , Liu Guokun , Zou Shouzhong , Ou Yang Liang-Yueh , Braun Trevor , Walker Marlon , Wheeler Daniel , Richter Lee , Josell Daniel
Published: February 2020

State of the art manufacturing of semiconductor devices involves electrodeposition of copper for device wiring and chip stacking. The success of the electroplating process depends on electrolyte additives that affect the local deposition rate to yield void-free superconformal, or bottom–up filling of trenches and vias that comprise 3D interconnects. Two distinct processes associated with the prerefential filling of recessed surface features, namely, curvature enhanced accelerator coverage and critical phenomena related to supressor induced negative differential resistance. Quantitative chemical process models based on the above processes have been shown to be effective in describing the filling of high aspect ratio features that range from nanometers (on-chip wiring1) to micrometers (through-silicon-vias2) to millimeters (printed circuit boards) in scale. Nevertheless, much remains to be known about the molecular nature of the additives and the competitive, co-adsorption dynamics involved in both suppression and acceleration of metal deposition. Accordingly, a variety of surface science tools, such as scanning tunneling microscopy (STM) and surface-enhanced infrared absorption spectroscopy (SEIRAS) are being used to investigate additive function. The lecture will detail experiments that reveal the important role of adsorbate water interactions, i.e. hydrophilicity, in the design and operation of additives used for superconformal film growth. The talk will conclude with a discussion of the lesson learned and their application to the deposition of other metals.
(Invited) Perspectives on Computational Studies of Electrocatalysis: New Approaches to Theoretical Catalyst Design
Authors: Greeley Jeffrey
Published: February 2020

Advances in the theoretical understanding of interfacial electrochemistry have, over the past decade, permitted the extension of periodic Density Functional Theory studies, which have traditionally been applied to probe chemistry at gas/solid interfaces, to electrochemical systems where potential-dependent structural and chemical phase transformations occur at liquid/solid interfaces. Indeed, such techniques have been employed to study a surprisingly wide class of electrochemical processes, ranging from electrocatalysis to corrosion, and are now being used to identify promising candidates for new electrocatalytic materials.

In this talk, I will begin with an overview of DFT-based predictions of electrocatalytic reaction mechanisms, with a particular focus on the Oxygen Reduction Reaction (ORR), which, given its mechanistic simplicity, has been a particularly fruitful target for computational research. I will summarize the several classes of materials that have been computationally investigated for this chemistry and will also seek to link recent results with experimental testing in practical membrane electrode assemblies. In the second part of the talk, I will describe some new methods that are being developed to increase both the fidelity and efficiency of computational electrocatalytic models, and I will provide examples of how these approaches are now yielding insights into electrocatalytic reactions with greater mechanistic and structural complexity.
(Invited) Molecular-Level Analysis of Electrodeposition Processes Using Theoretical Calculations and Surface Enhanced Raman Microscopy
Authors: Homma Takayuki , Kunimoto Masahiro , Onabuta Yusuke , Bertz Morten , Yanagisawa Masahiro
Published: February 2020

Electrodeposition process has been widely applied to various areas to form functional thin films and nanostructures. In order to understand the deposition process from molecular level to achieve further precise control, we employ theoretical calculation and surface enhanced Raman scattering (SERS). For the theoretical calculation to study the deposition reaction mechanism, molecular orbital and density functional theory calculations were applied to investigate the behaver of the species at the electrode surface, and various factors such as solvation effect and catalytic activity of the surface were also analysed. In addition, SERS equipped with confocal microscopy was used for in situ analysis of the reaction processes at the electrode surface. For this we applied plasmon sensors [1] to achieve very high sensitivity analysis. Furthermore multi-confocal type SERS microscopy was employed for mapping and imaging analysis. By using these techniques, various systems have been analysed and modelling of their reaction processes has been carried out.

This work was financially supported in part by “Development of Systems and Technology for Advanced Measurement and Analysis,” Japan Science and Technology Agency, and Grant-in-Aid for Scientific Research, MEXT, Japan.

[1] M. Yanagisawa, M. Saito, M. Kunimoto, T. Homma, Appl. Phys. Express, 9 , 122002 (2016).
(Invited) Multiscale Stress-Transport-Kinetics Continuum Models for Lithium-Metal Batteries-Relevance of Richard Alkire’s Electrodeposition Legacy for Next-Generation Batteries
Authors: Subramaniam Akshay , Jang Taejin , Dufek Eric J. , Subramanian Venkat R.
Published: February 2020

Multiscale is a term commonly used/abused in the literature. First, we will quantify the meaning of ‘multiscale’ models. Richard Alkire’s selected contributions in the field of electrodeposition – Multiscale models (continuum + KMC) and finite element methods for shape changes will be reviewed. The relevance of the same for the current hot-topic in the field of lithium-metal batteries – modeling, simulating and controlling the dendrite formation in lithium-metal batteries will be discussed.

There is significant interest in using pressure as an external control to achieve proper cyclability and desirable deposition characteristics in high energy-density lithium metal anodes. We aim to provide useful predictions of cell-level variables by using a multiscale approach in which local electrochemical effects of pressure and mechanical coupling in the anode are coupled with macro homogeneous models of porous cathodes to study the effect of pressure on voltage response. Progress made in multiscale models coupling stress, transport and kinetic models at different length scales and our perspectives will be presented. Our interest lies in efficient (ideally real-time) simulation of the coupled models.

Acknowledgements

The authors would like to thank for the financial support of this work by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the DOE through the Advanced Battery Material Research (BMR) Program (Battery500 consortium) and the Clean Energy Institute (CEI) at the University of Washington and the Washington Research Foundation (WRF) for their partial monetary support during this work.
(Invited) Exact and Approximate Methods for Analytical Modeling of Thermal and Electrochemical Transport in Li-Ion Batteries
Authors: Jain Ankur
Published: February 2020

This talk will summarize ongoing research on analytical modeling of thermal and electrochemical transport in Li-ion cells. These transport processes govern the performance and safety of Li-ion cells, and therefore are important to understand and optimize for a variety of electrochemical energy conversion and storage applications, such as grid energy storage, electric vehicles, aerospace, etc. Analytical models for steady-state and transient thermal behavior of a single cell will be presented. These models utilize well-known analytical techniques for solving the partial differential equations arising from the principle of conservation of energy. An iterative analytical model for thermal performance during cyclic operation will be presented. This model solves for the temperature distribution in a stepwise fashion, utilizing the temperature distribution at the end of each cyclic process as the initial condition for the next cyclic process. Approximate models for thermal runaway behavior will be introduced, highlighting the key role of thermal properties of the cell towards preventing thermal runaway. Important considerations related to the linearization of non-linear heat generation terms during thermal runaway will be discussed. Finally, modeling of phase change thermal management of Li-ion cells by integrating perturbation method based techniques with an iterative technique to solve coupled heat transfer problems will be discussed. These analytical methods help better understand the fundamental transport processes in a Li-ion cell, and are also often useful for correct experimental design and data analysis.
Linear Stability Analysis of Time-Dependent Electrodeposition in Charged Porous Media
Authors: Khoo Edwin , Zhao Hongbo , Bazant Martin Z.
Published: February 2020

We study the linear stability analysis of time-dependent electrodeposition in a charged random porous medium, whose pore surface charges can generally be of any sign, that is flanked by a pair of planar metal electrodes. Discretization of the linear stability problem results in a generalized eigenvalue problem for the dispersion relation that is solved numerically, which agrees well with the analytical approximation obtained from a boundary layer analysis valid at high wavenumbers. Under galvanostatic conditions in which an overlimiting current is applied, in the classical case of zero pore surface charges, the voltage and electric field at the cathode diverge when the bulk electrolyte concentration there vanishes at Sand's time. The same phenomenon happens for positive surface charges but at a time earlier than Sand's time. In contrast, negative surface charges allow the electrochemical system to sustain an overlimiting current via surface conduction past Sand's time, keeping the voltage and electric field bounded. Therefore, at Sand's time, negative surface charges greatly reduce the electrode surface instabilities while zero and positive surface charges magnify them. We compare theoretical predictions for overall electrode surface stabilization from the linear stability analysis with published experimental data for copper electrodeposition in cellulose nitrate membranes and demonstrate good agreement between theory and experiment. We also use the linear stability analysis as a tool to analyze how the crystal grain size changes with duty cycle during pulse electroplating.
Hollow Cathode Plasma (HCP) Enhanced Atomic Layer Deposition of Silicon Nitride (SiNx) Thin Films Using Pentachlorodisilane (PCDS)
Authors: Hwang Su Min , Kondusamy Aswin L. N. , Zhiyang Qin , Kim Harrison S. , Kim Jiyoung , Hwang Byung Keun , Zhou Xiaobing , Telgenhoff Michael , Young Jeanette
Published: February 2020

Silicon nitride (SiNx) films have drawn great attention due to the wide range of applications such as passivation layer, gate dielectric, spacer, charge trap layer, and diffusion barrier [1]. Conventionally used LPCVD and PECVD for SiNx deposition have limitations in terms of conformal deposition and thickness scalability. Since plasma enhanced atomic layer deposition (PEALD) is expected to overcome these shortcomings, several research groups have reported SiNx film deposition. A number of studies on PEALD SiNx process using various chlorine-containing silicon precursors have been reported due to their ease in synthesis as well as good thermal stability [2]. Recently, PEALD SiNx film using a novel chlorosilane precursor, pentachlorodisilane (PCDS, HSi2Cl5) with NH3/N2 plasma was reported [3]. Under the NH3/N2 plasma condition, PCDS enhanced the growth rate (approximately > 20 %) compared to the hexachlorodisilane (HCDS, Si2Cl6), but still showed relatively poor wet etch resistance. Inspired the film characteristics, we propose to explore the feasibility of improving the wet etch resistance of PEALD-SiNx films using the different gas mixture for plasma. It has been reported that the wet etch rate of SiNx films has a linear relationship with the hydrogen concentration in the films [1]. Compared to NH3/N2 plasma, N2-H2 (forming gas) plasma improves the wet etch rate possibly due to less N-H and H-N-H bonds in the SiNx films [2].

Herein, PEALD SiNx films using PCDS as Si precursor and N2-H2 (10 % forming gas) plasma as the reactant were evaluated. The combination with PCDS and N2-H2 plasma showed a relatively lower (approximately < 10 %) growth rate than NH3/N2 plasma under a range of process temperatures (270−300 °C) whereas the wet etch resistance to HF acid was improved (> 1.5 nm/min, 500:1 HF). Studying these results, we suggest the effect of hydrogen on film properties such as growth rate, film composition, and wet etch resistance.

[1] H.S. Kim, X. Meng, S.J. Kim, A.T. Lucero, L. Cheng, Y.C. Byun, J.S. Lee, S.M. Hwang, A.L.N. Kondusamy, R.M. Wallace, G. Goodman, A.S. Wan, M. Telgenhoff, B.K. Hwang, and J. Kim, ACS Appl. Mater. Interfaces 10, 44825 (2018).

[2] X. Meng, Y.C. Byun, H.S. Kim, J.S. Lee, A.T. Lucero, L. Cheng, and J. Kim, Materials 9, 1007 (2016).

[3] X. Meng, H.S. Kim, A.T. Lucero, S.M. Hwang, J.S. Lee, Y.C. Byun, J. Kim, B.K. Hwang, X. Zhou, J. Young, and M. Telgenhoff, ACS Appl. Mater. Interfaces 10, 14116 (2018).

Figure 1
(Invited) Electron Dynamics at the CuWO4/Electrocatalyst Interface for Photoelectrochemical Water Oxidation​
Authors: Hamann Thomas
Published: February 2020

Unraveling the electron dynamics at catalyst/electrode interfaces is critical for the development of design rules to produce efficient photoelectrochemical (PEC) water oxidation. Unlike the majority of photoanodes investigated for PEC water oxidation, the integration of catalysts with CuWO4 electrodes generally results in comparable or worse performance compared to the bare electrode. This is despite the fact that we have shown surface state recombination limits the water oxidation efficiency with CuWO4 electrodes and a catalytst ought to alleviate this reaction. Here we will present recent results which deepen the understanding of the energetics and electron-transfer processes at CuWO4/electrocatalyst interface which control the performance of such systems. Ni0.25Fe0.75Oy (denoted as Ni25) was chosen as a model catalyst, and through rigorous comparison of cyclic voltammetry, current transient and electrochemical impedance spectroscopy (EIS), intensity modulated photocurrent spectroscopy (IMPS), and dual-working electrode experiments measurements, we have been able to gain a significant insight into the role of the catalyst and the electron-transfer at the interface on the performance of CuWO4 for PEC water oxidation. General lessons and design rules for efficient PEC water splitting will be discussed.
Nanocomposites Based Self-Powered Electronic Systems: Investigating the Materials Properties for Energy Harvesters and Photodetectors
Authors: Aepuru Radhamanohar , Mangalaraja R.V.
Published: February 2020

Flexible electronic devices have drawn potential interest and provide significant new insights to develop energy conversion and storage devices such as photodetectors and nanogenerators. Recently, self-powered electronic systems have captivated huge attention for next generation MEMS/NEMS devices that can operate independently by generating built-in field without any need of external bias voltage and have wide variety of applications in telecommunication, imaging, environmental and defence sectors. The basic physical process involved in these devices are charge generation, separation, and charge flow across the electrodes. Many inorganic nanostructures have been exploring to fabricate various optoelectronic and electromechanical devices. However, the interaction of nanostructures and their excited charge carrier dynamics, photoinduced charge separation, and fast carrier mobility are yet to be studied. The proposed research is to address one such area and to realize the self-powered electronic devices.

In the present work, nanocomposites of inorganic nanostructures based on ZnO, metal halide perovskites; and Polyvinylidene fluoride (PVDF) based nanocomposites are realized for photodetectors and nanogenerators. The characterization of the inorganic nanostructures is carried out through steady state optical absorption and luminescence spectroscopies as well as X-ray diffraction and high-resolution transmission electron microscopy (TEM) studies. The detailed carrier dynamics is investigated using various spectroscopic techniques such as ultrafast spectroscopy and broadband dielectric studies. The developed composite nanostructures exhibit significant optical and electrical properties, which have wide potential applications in various MEMS/NEMS devices such as photodetectors and nanogenerators.
(Invited) Stretchable Conductive Nanocomposite for Soft Bioelectronics
Authors: Kim Dae-Hyeong
Published: February 2020

Intrinsically stretchable conductors form a vital component of advanced soft bioelectronics. And novel nanocomposites based on conductive nanomaterials have been used in diverse applications of implantable and wearable bioelectronics. Among many nanomaterials for the composites, silver nanowires (Ag NWs) have been popular. However, achieving highly conductive and soft composites simultaneously is challenging. Furthermore, because bioelectronics is necessarily exposed to biofluids, preventing Ag NW oxidation and Ag ion leaching is a significant challenge. Here we have achieved a highly conductive, biocompatible, and soft nanocomposite by using silver-gold (Ag-Au) core-sheath NWs and polystyrene-butadiene-styrene (SBS) elastomer. We synthesized ultralong Ag NWs encapsulated with a smooth and uniform Au sheath and then mixed them with the polymer. Phase separation of Ag-Au NWs and SBS occurs, which forms microstructures in the composite, reduces Young’s modulus, and increase softness and conductivity of the composite. We used the nanocomposite to fabricate a customized multi-channel soft cardiac mesh for the diseased swine heart. The mesh could be also fabricated as a wearable device which monitored electrophysiological signals and applied electrical and thermal stimulations on the human skin.
Interfacial Design of Metallic 1T-MoS2/Carbon Nanotubes for High-Electrocatalytic Hydrogen Evolution Performance
Authors: Geng Dongsheng , Jayabal Subramaniam
Published: February 2020

The development of effective non-noble metal based electrocatalysts for the electrocatalytic hydrogen evolution reaction (HER) at lower overpotentials has attracted tremendous attention due to its important role for various electrochemical energy storage devices.1,2

In this study, a simple hydrothermal approach is implied for the preparation of metallic 1T-MoS2/carbon nanotubes (1T-MoS2/CNTs), which acts as an efficient electrocatalyst for HER.3 Fig. 1a, b, and c show the TEM images of 1T-MoS2/CNT composite, in that the 1T-MoS2 consists of a few-layered nanometers in structure and the CNT are well distributed homogenously in the 1T-MoS2 nanosheets, which can reduce aggregation and restacking of the 1T-MoS2 nanosheets. In addition, it can be seen from the fig. 4d that the presence of more intrinsic defects in the 1T-MoS2 nanosheets (marked as circles) was observed, which might result in an expansion of the interlayer spacing. Moreover, the HRTEM image (Fig. 1d) confirmed the presence of the octahedral 1T phase (marked as square) in 1T-MoS2/CNT composite. Besides, 1T-MoS2/CNT composite has been characterized by EDX elemental mapping analysis (Fig. 1f), which shows the existence and homogeneous distribution of Mo, S, and C elements.

The tuning of catalytically more active sites and enhancement in the electron transport property can be achieved by designing of the defect-rich 1T-MoS2/CNTs composite material. The unique interfacial composition of the defect-rich 1T-MoS2/CNTs enables enhanced electrocatalytic HER performance with a low onset potential of 96 mV, a small Tafel slope of 54 mV dec-1 and low overpotential of 172 mV at a current density of 10 mA cm−2 (Fig. 1g). In addition, the 1T-MoS2/CNTs demonstrate superior long-term stability in acid conditions and the developed approach is easily applied to the large-scale production of efficient electrocatalysts. The electrocatalytic performance of 1T-MoS2/CNTs composite is also compared with the 1T-MoS2, CNTs, 2H-MoS2 modified electrodes and the commercial Pt/C catalyst.

This high-electrocatalytic HER performance is likely attributed to the synergistic effects between the MoS2 nanosheets and CNTS, and rich defects.4 Moreover, DFT calculations also have proved that 1T-MoS2/CNTs show higher free energy change for hydrogen adsorption (ΔGH) than the 1T-MoS2 and CNTs. This work provides a novel and simple strategy to design 1T-MoS2/CNTs for high-performance applications in energy storage fields.

References

1. S. Jayabal, G. Saranya, J. Wu, Y. Liu, D. Geng and X. Meng, J. Mater. Chem. A, 2017, 5, 24540-24563.

2. M. Chhowalla, H.S. Shin, G. Eda, L.-J. Li, K.P. Loh and H. Zhang, Nature Chem., 2013, 5, 263-275.

3. J. D. Benck, Z. Chen, L. Y. Kuritzky, A. J. Forman and T. F. Jaramillo, ACS Catal., 2012, 2, 1916-1923.

4. L.X. Chen, Z.W. Chen, Y. Wang, C.C. Yang and Q. Jiang, ACS Catal., 2018, 8, 8107-8114.

Figure 1
Nirh Nanosponges As Electrocatalysts for High-Performance Hydrogen Evolution Reaction
Authors: Nguyen Ngoc-Anh , Nguyen Van-Toan , Ali Yousuf , Choi Ho-Suk
Published: February 2020

In this study, we report a simple method to prepare NixRhy nanosponges while using NaBH4 as a reducing agent without using any surfactant for hydrogen evolution reaction in water electrolysis. The ratio of Ni and Rh has been changed to get various NixRhy electrocatalysts (Ni, Ni3Rh1, Ni1Rh1, Ni1Rh3 and Rh), respectively. Among the catalysts prepared, Ni1Rh3 electrocatalyst exhibited a high electrocatalytic activity with an overpotential of 48 mV at a current density of -10 mA.cm-2 and a superior stability even after 2000 cycles of CV in acidic electrolyte. In addition, the Ni1Rh3 electrocatalyst showed a good electrocatalytic activity in alkaline electrolyte compared to commercial Pt/C (20 wt% of Pt). In addition, the overall water splitting system of the Ni1Rh3 cathode and the commercial RuO2 anode was performed, not only exhibiting an excellent performance with a potential of 1.52 V (vs. RHE) at a current density of 10 mA.cm-2, but also proving very stable operation for over 100,000 seconds in 1.0 M KOH electrolyte.
(Invited) ZIF 67 Based Electrocatalysts As Highly Active Oxygen Electrodes for Water Electrolysis
Authors: Ghoshal Shraboni , Zaccarine Sarah , Anderson Grace C. , Martinez Madison B. , Hurst Katherine E. , Pylypenko Svitlana , Pivovar Bryan S. , Alia Shaun M
Published: February 2020

Huge overpotential losses emanating from oxygen evolution reaction (OER) is the primary concern toward establishing a sustainable hydrogen- based economy via water electrolysis. In alkaline environment, non- precious metals can be employed as OER electrocatalysts replacing expensive state of the art catalyst Iridium. In this work, ZIF 67 which is a zeolitic imidazolate framework (ZIF) containing Co as metal nodes has been reported with unprecedented electrocatalytic activity toward OER. Owing to intrinsic dynamic redox activity of Co (Co2+/Co3+) within the framework, accompanied by an efficient orbital overlap between Co and 2- methylimidazole, ZIF 67 exhibits unconventional charge conductivity compared to other commonly used ZIFs such as ZIF 8. This unusual characteristic eliminates the necessity to pyrolyze this material, as practiced frequently for ZIF based catalysts to achieve charge conductivity through carbonization. The major drawback of such heat treatment processes is the fact that a huge loss in catalyst weight and surface area occurs that compromise the performance and scalability of these catalysts. Herein, unpyrolyzed ZIF 67 based electrocatalysts have been reported which display very high activity toward OER in alkali; in three electrode cell as well as in single cell water electrolyzer. Controlled addition of dopants such as Fe, Ni and Zn has also been carried out to analyze the effect on the OER activity of ZIF 67. Further details on the structural aspect and thorough electrochemical characterization of the catalysts will be discussed in the presentation.

References

Zegers, P. J. J. o. p. s., Fuel cell commercialization: The key to a hydrogen economy. 2006,
154 (2), 497-502.

Burke, M. S.; Enman, L. J.; Batchellor, A. S.; Zou, S.; Boettcher, S. W. J. C. o. M., Oxygen evolution reaction electrocatalysis on transition metal oxides and (oxy) hydroxides: activity trends and design principles. 2015,
27 (22), 7549-7558.

Ma, T. Y.; Dai, S.; Jaroniec, M.; Qiao, S. Z. J. J. o. t. A. C. S., Metal–organic framework derived hybrid Co3O4-carbon porous nanowire arrays as reversible oxygen evolution electrodes. 2014,
136 (39), 13925-13931.
Influence of Α-Site Cations on Performance of Α2Ir2O7 Pyrochlore Oxygen Evolution Catalysts in Acidic Condition
Authors: Hubert McKenzie Austin , King Laurie Ann , Patel Anjli M , Bajdich Michael , Jaramillo Thomas F
Published: February 2020

The acidic nature of proton exchange membrane (PEM) electrolysis coupled with the highly oxidizing conditions of the oxygen evolution reaction (OER) greatly limits viable options for catalysts that are both active and stable. Precious metal catalysts, such as IrOx, are high performing OER materials, but scarcity and high cost may limit widespread implementation. Pyrochlore catalysts of the form A2B2O7 (where A is typically a rare-earth or alkaline-earth metal and B is a transition metal) have emerged as promising active candidates with reduced precious metal content and intriguing stability. For example, Y2Ir2O7 has demonstrated excellent activity and stability under acidic OER conditions despite some leaching of the Y cation, potentially leading to the in situ formation of a new active phase during catalysis1.

In this work, the influence of the A-site cation on the activity and stability of Ir-based pyrochlore materials (A2Ir2O7) was systematically explored. Using a series of rare-earth metals, activity and stability were experimentally correlated with changes in the physical, chemical, and electronic properties to better understand the origin of the enhanced performance. This experimental work was supported by density functional theory (DFT) calculations. The fundamental insight gained will help to design OER catalysts with improved activity and reduced precious metal content, all without compromising stability.

Cyclic voltammetry, chronoamperometry, chronopotentiometry, and double layer capacitance were used to determine the electrochemical performance of the catalysts. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify leaching of the A-site cations and Ir under acidic OER conditions and establish a relationship between the loss of material and the change in catalytic performance. This relationship was further investigated with DFT calculations. Additionally, the crystal structure, surface composition, and morphology of the catalysts before and after electrochemical testing were probed using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM).

References:

Lebedev, D. et al. Highly Active and Stable Iridium Pyrochlores for Oxygen Evolution Reaction. Chem. Mater. (2017). doi:10.1021/acs.chemmater.7b00766
Highly Conductive Catalyst with Advanced Manufacturing for Efficient Oxygen Evolution Reaction
Authors: Yang Gaoqiang , Yu Shule , Li Yifan , Kang Zhenye , Bender Guido , Pivovar Bryan S. , Green Johney , Cullen David A. , Zhang Feng-Yuan
Published: February 2020

The electrochemical water electrolysis is a convenient technique to store intermittent, sustainable energies, such as solar and wind, into high-purity hydrogen. The state-of-the-art electrocatalysts for oxygen evolution reaction (OER) are Ir/Ru-based materials. However, their scarcity and high costs hamper the industrialization of water electrolysis. In addition, the low electrical conductivity (~ 1000 Ω/□) of those catalysts and the sluggish multistep proton-coupled electron transfer of OERs significantly reduce the reaction sites and performances of water splitting.

To overcome those problems, this research will present a highly conductive multi-layer catalyst fabricated with advanced manufacturing methods. We employ spray printing, sputter coating, and inkjet printing to produce nafion layers, gold nanolayers (AuNL), and IrO2 catalyst layers, respectively. The mesoporous AuNLs provide the catalyst layer with not only excellent electrical conductivity (0.5 Ω/□) but also good proton permeability. Furthermore, the novel structure of the multi-layer catalyst in the electrolyser cell helps to directly investigate the influence of conductivity on OER kinetics by visualizing the generated oxygen bubbles, which enables the establishment of correlation between the conductivity and reaction sites. Most importantly, the faster OER kinetics can be achieved even with a much lower loading of IrO2 catalysts (as low as 0.1 mg/cm2) than the conventional IrO2 catalyst layer in pure water, acidic, and alkaline solutions. The novel multi-layer catalyst provides a new way to enhance the performance and reduce the usage of noble catalysts in energy conversion and storage devices.

Keywords: Inkjet printing, mesopores, high conductivity, ultra-low catalyst loading, water electrolysis.
Composite of Nickel Oxide Hexagonal Sheet Supported on Carbon Nitride for Photo-Electrochemical Water Splitting
Authors: Chaudhary Preeti , Ingole Pravin Popinand
Published: February 2020

Developing highly efficient and cost-effective electro-catalysts for the photo-electrochemical (PEC) water splitting is of great significance, since its two reactions, oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is coupled with the key clean energy systems. However, the prohibitive costs and scarcity of precious metals used as OER and HER catalysts (e.g. IrO2, RuO2, Pt) limits the large scale commercialization. Herein, we report a facile and cheap novel organic-inorganic hetero-structured electro-catalyst: 2D nickel oxide (NiO) hexagonal sheet supported on graphitic-carbon nitride (g-C3N4) which has been successfully synthesized using in-situ solid-state heat treatment. The Transmission electron microscopy (TEM) characterization confirms that NiO are homogeneously dispersed on the surface of g-C3N4. The presented catalyst display outstanding activity in catalyzing PEC water splitting with a potential of 130 mV for OER and 5 mV for HER for the reaction to start. Moreover, the maximum current density obtained at an overpotential of 200 mV are 20 mAcm-2 and 1000 mAcm-2 for OER and HER, respectively. Our findings reveal that the rational interaction between two-dimensional materials can remarkably promote the hydrogen and oxygen production reactions, thus boosting the entire clean energy system. Furthermore, our work also reveals the importance of local transition metal coordination in catalysts for the OER and HER which would lead to new class of low-cost, durable and efficient water splitting catalysts.

Figure 1
Hydrogen Evolution Reaction Catalyzed By Plasmoinic Photo-Electrodes Under Visible Light Illumination
Authors: Minamimoto Hiro , Sato Daiki , Murakoshi Kei
Published: February 2020

From the environmental point of view, the efficient control of the visible light driven hydrogen evolution reaction is one of the promising issue. For that, the semiconductor electrode can be regarded as the sufficient material but various semiconductor electrodes cannot be used for the visible light driven reactions due to their wide band gap energy. Recently, plasmoic photoelectric conversion system, which is the introduction of the plasmon active metal nano-structures onto the surface of the semiconductor substrate, has been received much attention due to its wide range photo response abilities. In this system, the electrons are excited and injected into the conduction band of the n-type semiconductor under visible light illuminations. Up to now, various plasmon-induced chemical reactions, even the water splitting, have been established. However, although well-established systems have been reported, the direct control of the reduction reaction at the metal-semiconductor interface using the excited electrons has not been well examined because the almost plasmonic photoconversion systems consist of the n-type semiconductor electrode and used the generated holes for the reactions. In this study, we have tried to establish the plasmon-induced hydrogen evolution system by using p-type semiconductor substrate and plasmon active nano-structures. By the fabrication of the plasmonic Ag dimer structures, we have observed the generation of the photo-current derived from the hydrogen evolution reactions under visible light illumination. Through the photocurrent measurements and the incident photon to current conversion efficiency obtained under different pH conditions, we have confirmed the pH dependence of the photo current value and the photo response characters. In addition to these, as the very interesting point for the current study, we have found the very unique catalytic property for the plasmonic hydrogen evolution especially under specific pH condition. Through the various photoelectrochemical measurements including isotropic selectively, we are sure that our plasmonic hydrogen evolution system could be one of the good candidate for future light energy conversion system.
Polysulfone-Based Membranes for Vanadium Redox-Flow Batteries
Authors: Karpushkin Evgeny A. , Komayko Alena I , Timoshenko Vadim A , Sergeyev Vladimir G.
Published: February 2020

Redox flow batteries have been recognized as promising electrochemical energy storage devices, due to independent power and energy scaling, long cycle life, fast response, and no self-discharge during storage. A crucial part of a redox flow cell is the membrane which separates the anolyte and catholyte containers. A membrane for vanadium redox flow battery (VRB) should be stable and exhibit high proton conductivity as well as low vanadium species permeability.

Perfluorinated ion-exchange membranes such as Nafion® are currently among the most widely used separators for VRBs. However, the best-performance membranes recognized so far are generally expensive, and the crossover of vanadium species across the membrane is noticeable. Therefore, if a cheaper alternative membrane material is found, the cost efficiency of the battery will be improved.

We have evaluated earlier the applicability of membranes based on polyacrylonitrile (PAN) in redox-flow batteries using VBR as a model system. It has been shown that the tuning of PAN material microstructure via phase separation and/or hydrolysis provides the desired balance of proton conductivity and vanadium species permeability. The overall energy efficiency of the VBR cell built using the PAN-based membranes has been found comparable to that determined with Nafion® membranes.

In this contribution, we extended this approach to the manufacture of membranes based on polysulfone (PS). The porosity and hydrophilicity of the PS membranes was tuned via phase separation, incorporation of polymeric (poly-N-vinylpyrrolidone) or inorganic (silica) additives, and the procedure of the membrane conditioning. Major physico-chemical properties of the membranes (ion conductivity and water permeability) were systematically measured, and the operation of the model VRB assembled using the PS-based membranes was evaluated in comparison with the PAN and Nafion® membranes.

This study was financially supported by Russian Science Foundation (project no. 17-73-30006).
Lung-Inspired PEM Fuel Cells Built from Layered Printed Circuit Boards
Authors: Bethapudi Viswanath Sasank , Cho Jason I.S , Hack Jennifer , Shearing Paul R. , Brett Dan J.L , Coppens Marc -Olivier
Published: February 2020

Homogenous, scalable, and uniform distribution of reactants at membrane-electrode assembly (MEA) level are critical to the performance of polymer electrolyte membrane (PEM) fuel cells. To achieve this, cathode flow fields were introduced that have fractal flow geometry, inspired by the air flow mechanism in lungs [1]. These were manufactured using direct metal laser sintering. Here, we discuss the design and characterisation of lung-inspired fuel cell flow plates using cheap and light printed circuit boards (PCBs) manufactured using computer numeric control (CNC) machining. X-Ray computed tomography (CT) scans of the developed fractal flow fields demonstrate a uniform and well aligned PCB plate assembly that results in a fractal hierarchy of flow channels, as shown in figure (1a) and (1b). Polarization performance at 70% reactant humidity and 45oC cell temperature for the fractal flow field was 12% higher than the performance of a single-serpentine, at 0.6V individual cell potential, as shown in figure (2).The cell temperature profile for the fractal flow field was more stable and uniform, compared to a rapid rise in profile of the single-serpentine one. The voltage decay measurements, at constant current density hold, indicate that voltages of fractal and single-serpentine flow fields vary within 2% and 6% of their initial voltage values, respectively, over a period of 6h continuous operation. Furthermore, Electrochemical Impedance Spectroscopic (EIS) measurements establish higher ohmic and mass transport resistances for the single-serpentine compared to the fractal flow field, at current densities ranging between 100mA/cm2 and 900mA/cm2.

Keywords: Fractal, X-Ray CT, EIS,CNC, PCB, lung-inspired, hierarchical

Reference:

[1] P. Trogadas, J.I.S. Cho, T.P. Neville, J. Marquis, B. Wu, D.J.L. Brett and M.-O. Coppens, 2018, A lung-inspired approach to scalable and robust fuel cell design. Energy & Env. Sci. 11, 136-143.

Figure 1