bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Extensive Study of the Electrical Conduction in HKUST-1 Single Crystals
Authors: Koh Sang-Gyu , Nakaune Yusuke , Hachida Momoka , Morita Takumi , Kinoshita Kentaro 
Published: May 2020

Metal-Organic Frameworks (MOFs), which is three-dimensional (3-D) nanoporous materials composed of metal ions and organic ligands coordinated together, has recently attracted enormous attention as functional materials for electronic devices owing to their structural and functional flexibility in the design, as well as relatively high thermal stability [1, 2]. Although there are some reports so far that guest molecule doping drastically improves the electrical conduction of MOFs, e.g. the electrical conductivity of HKUST-1 (Cu3(btc)2) increases by infiltration of TCNQ, most of those experiments has been done using pellet or polycrystalline film samples [3, 4]. To extract an intrinsic electrical current conduction, avoiding the influences of grain boundaries and the residual stress introduced into the film due to the substrate mismatching, the use of single crystalline sample is essential.
In this work, we investigated the dominant conduction mechanism of TCNQ-infiltrated bulk HKUST-1 single crystals which include much less grain boundaries and residual stress, by measuring the electrical conductivity as functions of a bias voltage, temperature, and pressure.
Sub-mm sized HKUST-1 single crystals were fabricated and infiltrated with TCNQ using a saturated TCNQ/CH2Cl2 solution. The temperature dependence of DC current between 30 °C to 110 °C in the ambient shows that a current at 10 V decreases with increasing temperature down to undetectable value of less than 1 x 10-12 A, although the current value at 30 °C of around 1 x 10-6 A is similar to that of polycrystalline films [3]. We also confirmed that the temperature dependence of DC current for un-infiltrated HKUST-1 single crystals almost agrees with those of the TCNQ-infiltrated ones. Therefore, TCNQ infiltration is not effective in improving an electrical conductivity and the relatively high electrical conductivity at 30 °C is attributed to the presence of water absorbed by samples from the ambient, which was confirmed by thermogravimetric analysis. These results indicate that the current we measured was attributed to the ionic conduction probably due to the electrolysis of water inside the nanoporous structure not to the electronic conduction. Therefore, it is implied that the drastic improvement of the conductivity in the TCNQ-infiltrated HKUST-1 reported in ref. [3] is due to the use of film instead of bulk single crystal. It is suggested that the residual stress introduced into the HKUST-1 film by substrate mismatching plays a key role in the improved electronic conduction of the TCNQ-infiltrated HKUST-1 system. We will also discuss the effect of applying high pressure to the single crystals.
References
[1] G. Wu et al., J. Am. Chem. Soc. 2017, 139, 1360−1363.
[2] Y. Liu et al., Angew.Chem.Int.Ed.2016,55,8884–8888.
[3] A. A. Talin et al., Science, 2014, 343, 66-69.
[4] M. R.-Torrente et al., Phys.Chem.Chem.Phys., 2019, 21, 25678.
Morphology, Composition and Sensor Performance of Nanoporous Au(Pt)
Authors: Wong Timothy , Ebrahimy Amirhossein Foroozan , Langelier Brian , El-Zoka Ayman Amr , Newman Roger C. 
Published: May 2020

Recent atom-probe tomography (APT) and ATEM studies of dealloyed layers in binary AgAu and ternary AgAuPt alloys showed the various ways in which more-noble elements enrich during dealloying, at the atomic scale (1). We have since extended this research in several directions – towards less expensive alloys, lean in more-noble elements, and towards the potential applications of such materials in gas sensing.
In this presentation, we will start with a review of published and unpublished data from the APT study, which was done using alloys with 23 at% (Au + Pt). New information will then be shown for alloys with less than 6 at.% (Au + Pt). The dealloyed layers are very Ag-rich, and very interesting conflicts arise between enrichment of the more-noble element(s) on the ligament surfaces and the ultimate supply of those elements.
For gas sensing applications, we take advantage of the effect of adsorption on ligament surfaces on electron scattering during conduction in the confined metal phase. Delicate impedance measurements at the milli-ohm level show that two kinds of environmental effect can be distinguished. Adsorption of water or other gases up to several molecular layers induce changes in the measured resistance of the metal phase, while thicker layers induce a double-layer charge separation leading to capacitive changes.
In Situ UV-Visible Optical Spectroscopy Study of Nanoporous Gold Formation By Electrolytic Dealloying
Authors: Chacko Joel , Corsi John S , Welborn Samuel S. , Detsi Eric 
Published: May 2020

Thin films of nanoporous gold (NP-Au) have been extensively studied for localized surface plasmon resonance [1,2], showing a strong structure-property relationship between the morphology of the porous network and resonant frequencies. In this talk, I will show how we take advantage of this structure-property relationship and use UV-Visible optical spectroscopy to study the morphology evolution in NP-Au thin films in situ during selective electrolytic leaching of the sacrificial Ag from Au-Ag parent alloy. The evolution of plasmon resonance frequencies obtained from in situ UV-Vis spectra are directly linked to the morphology evolution (development of pores and changes in structure size) and the chemical composition (change in Ag content) in NP-Au, as confirmed by ex situ electron microscopy data.
[1] A. Pröschel, J. Chacko, R. Whitaker, M. A. U Chen, and E. Detsi: Journal of The Electrochemical Society 166, H146-H150 (2019).
[2] E. Detsi, M. Salverda, P.R. Onck and J.T.M. De Hosson:
Journal of Applied Physics 115, 044308 (2014)
Modeling of Li-Ion Batteries with Highly-Ordered Hierarchical Electrode Design
Authors: Goel Vishwas , Chen Kuan-Hung , Namkoong Min Ji , Yang Chenglin , Kazemiabnavi Saeed , Mortuza S. M. , Mazumder Jyoti , Sakamoto Jeff , Dasgupta Neil P. , Thornton Katsuyo 
Published: May 2020

The advent of battery-powered electric vehicles has generated a need for batteries that are both energy and power dense. Traditionally, thick electrodes with heavy active material loading are used for enhancing the energy density of a battery. However, thick electrodes (with a loading of > 2.5 mAh/cm2) limits the ionic transport inside the electrode, thereby limiting the power density of the battery1. Decreasing the thickness of the electrodes, as well as increasing the porosity, can enhance the power density of a battery, but this increases the fraction of electrochemically inactive materials, such as current collectors, separator, and packing material, leading to reduced energy density. Therefore, the conventional electrode design is constrained by the tradeoff between the energy density and power density.
In this presentation, we examine the role of channels within a thick anode in reducing the ionic transport limitation2,3. We apply the porous electrode model4 to simulate the effect of the channels on the ionic concentration gradient and reaction rate, as well as the resultant rate capability of the cell. We will describe the parameterization of the model using three-electrode measurements. The model results show substantial improvement in the electrolyte salt concentration because of channels as compared to that in the conventional electrodes at high charge rates such as 4C and 6C.
References:

1. Gallagher, K. G. et al. Optimizing areal capacities through understanding the limitations of lithium-ion electrodes. J. Electrochem. Soc.
163, A138–A149 (2016).
2. Kim, Y., Drews, A., Chandrasekaran, R., Miller, T. & Sakamoto, J. Improving Li-ion battery charge rate acceptance through highly ordered hierarchical electrode design. Ionics.
24, 2935–2943 (2018).
3. Nemani, V. P., Harris, S. J. & Smith, K. C. Design of bi-tortuous, anisotropic graphite anodes for fast ion-transport in Li-ion batteries. J. Electrochem. Soc.
162, A1415–A1423 (2015).
4. Newman, J. & Tiedemann, W. Porous-Electrode Theory with Battery Applications. AIChe J.
21, 25–41 (1975).
Assessing pH and Voltage Effects on the Binding of CO to Model Copper Catalyst Surfaces Via a DFT-Continuum Theory
Authors: Weitzner Stephen Eric , Akhade Sneha A , Varley Joel Basile , Feaster Jeremy T. , Wood Brandon C. , Baker Sarah E , Duoss Eric B , Corral Daniel , Otani Minoru 
Published: May 2020

The electrochemical conversion of CO2 to commodity products such as hydrocarbons and oxygenates is an attractive approach for generating non-fossil derived chemical and fuel stocks and for the storage of energy in chemical bonds. To date, a number of studies have shown that the activity and selectivity of copper-based catalysts for the CO2 reduction reaction towards valuable higher order carbon products are highly sensitive to the local reaction environment. Furthermore, the local electrolyte concentration and local pH is intimately tied to the applied voltage and the mass transport of reactants and products within the interfacial region. In recognition of this, several recent efforts focused on engineering the design of electrochemical reactors to reduce mass transport limitations indicate a pronounced effect on the apparent selectivity of the copper catalyst. While these efforts have highlighted a new direction for improving the efficiency of the CO2 reduction reaction, the rational design of these reactors remains challenging due to the need to optimize features of the reactor across multiple time and length scales. In this talk, we will discuss recent efforts within our laboratory to address the influence of the local pH on the CO2 reduction reaction at the atomistic level. We focus the discussion on the binding of CO, a key reaction intermediate in the CO2 reduction pathway, whose preferential hydrogenation or dimerization leads to the production of C1 and C2 products, respectively. We additionally demonstrate how the use of hybrid approaches employing density functional theory (DFT) and continuum models can help bridge time and length scales within the context of atomistic CO2 electroreduction modeling.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Theoretical Analysis of Photo- and Electrochemical Properties of Anatase Nano-Particles
Authors: Juhasz Gergely 
Published: May 2020

Oxide nanoparticles, like TiO2 nanoparticles are often applied in electrodes and photocatalytic systems. We studied the electronic states around the bandgap in anatase-type TiO2 nanoparticles of different shapes with (101) and (001) facets using Density Functional based Tight Binding (DFTB) method. Previous calculation has already shown that most orbitals of the valence and conduction bands forms delocalized band-like orbitals, however there are a significant number localized states at the lower at edge of conduction band, too.
The energy and position of these unoccupied localized orbitals can be controlled by the shape of the nanoparticle and these orbitals can play important contribution to both electrochemical and photochemical properties. TD-DFTB calculations showed that the optical spectrum around the band gap is dominated by few transition with large oscillator strength (see Figure), while most of the transitions give only a weak contribution.

Figure 1
(Invited) Electrons in Two-Dimensional Materials: Mobility and Catalysis
Authors: Liu Yuanyue 
Published: May 2020

Two-dimensional (2D) materials possess attractive properties for many applications such as (opto)electronics and electrocatalysis. However, their developments are impeded by a number of significant challenges, many of which root in the 'problems of electrons'. On the physics side, the electrons/holes in current 2D semiconductors do not move fast enough under electric field (i.e. low mobility), impeding their use in high-performance electronics and optoelectronics. On the chemistry side, the current 2D electrocatalysts still suffer from relatively low activity/selectivity, hindering their use in efficient energy conversion. These challenges urge for an improved understanding of the electrons in 2D materials, and using these insights to design/discover 2D host materials with better performance.
Here I will discuss our recent progress in understanding the physics and chemistry of electrons in 2D materials, including: (1) why 2D semiconductors tend to have a low mobility, and the guidelines towards high-mobility semiconductor [1,2]; (2) the effects of surface charge [3] and water molecules on electrocatalysis, with which we can explain some puzzles in electrochemical CO2 reduction catalyzed by single metal atom in graphene [4] .
[1] L. Cheng, Y. Liu, JACS, 2018 DOI: 10.1021/jacs.8b07871
[2] L. Cheng, C. Zhang, Y. Liu, JACS 2019 DOI: 10.1021/jacs.9b05923
[3] D. Kim, J. Shi, Y. Liu, JACS, 2018, 140, 9127
[4] X. Zhao, Y. Liu, in preparation
First Principles Simulations of Surface Modified TiO2 for CO2 Activation
Authors: Nolan Michael 
Published: May 2020

Replacing liquid fossil fuels with renewable fuels produce from water and CO2 is a key challenge for the 21st century. This is linked with both the increase in world energy demand and the climate emergency. Two potential technologies than will alleviate these issues are replacing liquid fuels with hydrogen for transport and capturing & converting CO2 produced in industrial process to useful chemicals with the former integrated with CO2 capture to drive conversion to e.g. methanol or C2 compunds. If these process are further driven by solar energy or other renewable energy, then the processes will be fully renewable.
In this presentation we describe our work on density functional theory simulations of modifications to TiO2 rutile and anatase surfaces by nanoclusters of metal oxides and explore the possibility for these heterostructures to promote CO2 activation and reduction. We show that modifying TiO2 with metal oxides produces stable heterostructures with potential band gap reduction towards the visible region of the electromagnetic spectrum, while these structures also promote charge localisation and oxygen vacancy formation. #for CO2 conversion we identify oxide modifiers to TiO2, namely CuOx, Bi2O3, CeO2 and Cr2O3 that can activate or even directly dissociate CO2 to CO. Low loadings of Cu appear to be most favourable for CO2 activation by promoting reduction of the TiO2 substrate; the electrons released by reduction are transferred to CO2 to give a carboxyl species which is an important intermediate in hydrogenation of CO2. Bi2O3 species are able to adsorb and activate CO2, producing a range of adsorbed species, but upon reduction can promote electron transfer to form a carboxyl or break a C-O bond and produce CO. Key aspects appear to be the presence of active sites as a result of oxide reduction, the presence of reduced cations and the electronic structure of the modifiers. Comparison with experimental results will also be presented.
(Invited) Synthesis and Electrochemical Study of Gold Based Nanomaterials
Authors: Chen Aicheng , Liu Zhonggang , Hossain Md Nur , Manikandan Venkatesh , van der Zalm Joshua 
Published: May 2020

Gold-based nanomaterials have received increasing attention in a wide range of energy, environmental and medical applications due to their unique physicochemical properties, chemical robustness, and distinct catalytic activities [1-5]. In this presentation, we mainly focus on the synthesis and modification of nanoporous Au as well as its promising energy, environmental and biological applications. The primary strategies for the fabrication of nanoporous gold, including chemical dealloying, electrochemical alloying/dealloying, and dynamic hydrogen bubble template approach, will be presented. The development of nanoporous gold based electrochemical sensors for the detection of biomarkers, contaminants, and food additives will be highlighted. In addition, the high catalytic activity of nanoporous gold towards the electrochemical reduction of carbon dioxide will be discussed.

References

[1] Z. Liu, A. Nemec-Bakk, N. Khaper, A. Chen, Anal. Chem. 89 (2017) 8036-8043
[2] V.S. Manikandan, B.-R. Adhikari, A. Chen, Analyst 143 (2018) 4537-4554
[3] M.N. Hossain, Z. Liu, J. Wen, A. Chen, Appl. Catal. B: Environ. 236 (2018) 483-489
[4] Z. Liu, V.S. Manikandan, A. Chen, Current Opin. Electrochem. 16 (2019) 127-133
[5] Z. Liu, E. Puumala, A. Chen, Sens. Actuators B: Chem. 287 (2019) 517-525.
(Invited) Enhancement of Oxidation of Dimethyl Ether at Nanostructured-Metal-Oxide-Supported Noble Metal Catalytic Nanoparticles: Comparison to Behavior of Other Simple Organic Fuels
Authors: Rutkowska Iwona Agnieszka , Kulesza Pawel J. 
Published: May 2020

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.
Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.
We pursue a concept of utilization of zirconia nad mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of dimethyl ether relative to methanol, formic acid and ethanol. Among important issues is incorporation of additional metal (e.g. Rh or Pt) nanostructures capable of weakening, or even breaking, the C-C and C-O bonds in the ethanol and dimethyl ether molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol and dimethyl ether are partitioned (at Rh, Pt or Pd) to methanolic residues and further oxidized at PtRu cannot be excluded.
(Invited) Cathodic Corrosion of Polycrystalline Au Electrodes: Applications in Electrocatalysis and Surface Spectroscopy
Authors: Kibler Ludwig A. , Elnagar Mohamed M. , Hermann Johannes M. , Jacob Timo 
Published: May 2020

Faceting and nanostructuring of polycrystalline Au electrodes by cathodic corrosion in concentrated aqueous alkali metal hydroxide electrolytes have been studied systematically. Scanning electron micrographs show the formation of octahedral Au nanocrystals and triangular pits by using NaOH and KOH solutions, respectively. These Au surfaces with preferential (111)-texture and a unique nanostructure are of special interest for new developments and applications in electrocatalysis and surface-enhanced Raman spectroscopy (SERS).
Cathodic corrosion of Au leads to a single-crystal-like electrochemical behavior with characteristic features of Au(111) electrodes. The electrocatalytic behavior of this new type of nanostructures will be presented for the hydrogen evolution reaction (HER) and for the formic acid oxidation reaction (FAOR).
The Raman activity of adsorbed pyridine on the nanostructured Au electrodes was studied with SERS. While untreated polycrystalline Au is not SERS-active, the use of cathodic corrosion opens up a way for in-situ SERS-applications in electrochemistry.

Figure 1
Nanoporous Copper from Electrochemical Dealloying of Brass
Authors: Ebrahimy Amirhossein Foroozan , Newman Roger C. 
Published: May 2020

Copper based catalysts have been shown to reduce CO2 electrochemically into hydrocarbons and oxygenates with high Faradaic efficiencies [1]. The selectivity and the efficiency of CO2 electroreduction could benefit from morphological studies on Cu nanocatalysts. Among several methods of fabricating Cu nanocatalysts, dealloying, i.e., the selective electrolytic dissolution of a less-noble element from an alloy [2], is one of the most flexible, controllable, and economical methods available to date. The product of this dissolution is a metallic nanoporous material: an interconnected ligament-pore structure with nearly zero net curvature.
Building on the previous investigations on dezincification of brass [3], the evolution of nanoporous Cu from dealloying Muntz metal (Cu60Zn40) will be presented. The effect of various dealloying parameters, such as anodic potential, temperature, pH, and electrolyte will be resolved via various advanced characterization techniques.
[1] C. T. Dinh et al., “CO2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface,” Science, vol. 360, no. 6390, pp. 783–787, 2018.
[2] R. C. Newman, S. G. Corcoran, J. Erlebacher, M. J. Aziz, and K. Sieradzki, “Alloy corrosion,” MRS Bull., vol. 24, no. 7, pp. 24–28, 1999.
[3] R. C. Newman, T. Shahrabi, and K. Sieradzki, “Direct electrochemical measurement of dezincification including the effect of alloyed arsenic,” Corros. Sci., vol. 28, no. 9, pp. 873–886, 1988.