bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Correlation in 2D Materials: Proximity Effects and Reactivity through the Lens of Quantum Monte Carlo
Authors: Rubenstein Brenda Marilyn , Sprague Leonard , Nanguneri Ravindra , Iyer Gopal
Published: May 2020

2D materials are an exciting new class of materials promising for a wide range of engineering applications because of their exceptionally tunable electronic properties; indeed, these materials’ band gaps, charge densities, and spin densities can be dramatically altered just by stretching, compressing, or stacking them. Despite their promise, however, our modern understanding of 2D materials is partially obscured by the fact that most have only been computationally modeled using Density Functional Theory (DFT), a theory that cannot readily describe electron correlation and is known to yield widely varying results for such integral quantities as band gaps and molecular binding energies depending upon the exchange-correlation functional employed. In this talk, I will describe our recent efforts to model an array of 2D materials using fully correlated quantum Monte Carlo (QMC) techniques and the unanticipated physics these efforts have revealed. First, we will discuss for which materials our simulations reveal the largest discrepancies between DFT and QMC. We will then illustrate the importance of using correlated methods in the modeling of proximity-induced magnetism and spin-orbit coupling in multilayer materials. Lastly, if time permits, we will detail how correlation influences carbon dioxide reduction on post-transition metal chalcogenides. Altogether, this work paints a more complete picture of the electronic structure of this increasingly important class of materials.
Calculation of Coverage-Dependent Catalytic Activity for Alloy Nanoparticles with Experimentally Relevant Sizes
Authors: Cao Liang , Mueller Tim
Published: May 2020

We present the use of ab-initio calculations to calculate the coverage-dependent catalytic activity of alloy nanoparticles with experimentally relevant sizes (5 nm ‒ 10 nm) by explicitly predicting atomic-scale structures and adsorbate binding energies. We demonstrate our approach using Pt–Ni nanoparticles as catalysts for the oxygen reduction reaction (ORR). We achieve our results by constructing a quaternary Pt‒Ni‒OH-Vacancy cluster expansion model to explicitly predict OH adsorption energies on nanoparticles of varying shape, size, and atomic structure. The OH coverage-dependent ORR activity is calculated through a kinetic Monte Carlo (KMC) simulation. This model enables us to accurately investigate the catalytic activity of various surface sites with different coordination numbers and local atomic environments. Using this model, we evaluate how different parameters affect the ORR activity of Pt–Ni nanoparticles, including size (2 nm ‒ 10 nm), Pt composition (50% ‒ 100%), and shape. Through the use of KMC-enabled kinetic simulations of structural evolution we evaluate how the activities of the particles change due to Ni dissolution. Our approach identifies OH coverage at the atomic scale and provides theoretical insights into how to tune the structures of alloy nanoparticles to optimize catalytic activity.
(Invited) Discovery and Design of Alloy Catalysts and Lithium-Ion Battery Materials through Machine Learning
Authors: Mueller Tim
Published: May 2020

Drawing on examples from alloy catalysis and lithium-ion batteries, I will demonstrate how machine learning can be used to significantly accelerate the design and discovery of new materials. In the first example, I will present a way to create complete maps of the surface structures and catalytic properties of an alloy catalyst at every point in its phase diagram. The key to this approach is the generation of surface cluster expansions that depend on the lattice parameter of the bulk material and are trained using a Bayesian method. I will discuss how these maps reveal insights into the catalytic properties of intermetallic phases and demonstrate how the maps can be used to rapidly identify the target synthesis conditions for stable and active catalysts. In the second example, I will demonstrate how training an interatomic potential model using on-the-fly machine learning can accelerate the calculation of activation energies for lithium diffusion by seven orders of magnitude, resulting in significantly improved agreement with experiment compared to pure density functional theory. Using the machine-learned interatomic potential models, we have identified new candidate coating materials designed to improve interfacial stability in solid state lithium-ion batteries.
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.
The Effect of Epoxy Group on Ethylene Carbonate Decomposition at Carbon Anode of Sodium Ion Batteries: Theoretical Study
Authors: Watthaisong Panuwat , Suthirakun Suwit , Hirunsit Pussana
Published: May 2020

Sodium-ion batteries (SIBs) have received much attention as promising alternatives to Li-ion batteries as large scale and low-cost energy storage systems owing to close electrochemical similarity between lithium and sodium, and the natural abundance of sodium resources. However, many challenges must be overcome to make SIBs well-positioned in commercialization such as low cyclability, and low stability of the solid-electrolyte interphase (SEI) formation, results from the decomposition of organic solvents in the electrolyte on the anode of SIBs. The SEI has a profound effect on cycle life and performance of the batteries. Therefore, understanding the SEI compositions and its formation mechanisms is crucial for SIBs development. Carbon-based anode materials are commonly used as the anode for SIBs because of their appropriate electrochemical properties, an abundance of carbon and safety. The oxygen-containing groups often present in the carbon-based anode and they usually actively involved in chemical reactions. In this work, we performed density functional theory (DFT) calculations to elucidate the effect of oxygen containing group of epoxy on decomposition mechanisms at the initial stages of sodiation of ethylene carbonate (EC) molecule which is one of common electrolytes applied in ion-battery. The calculation results indicated that EC decompositions on pristine graphene were initiated by CE-OE bond cleavage which is rate-limiting step followed by Cc-OE bond cleavage in the second step producing CO2 and acetaldehyde as products (Figure 1). The presence of an epoxy group on graphene does not directly change the mechanisms, however, it significantly increased the activation barriers on all decomposition pathways compared to those on pristine graphene. The strong electrostatic interaction between negatively charged epoxy group and positively charged Na ion weakens interaction between EC and carbon surface. Also, the presence of an epoxy group facilitates carbon surface to be more positively charged and electron transfer to EC is less favorable than that on pristine graphene. Furthermore, we investigated the solvation effect on the mechanisms by increase the number of EC molecules to model a solvation shell. The results showed that the inclusion of the electrolyte environment reveals other possible decomposition mechanisms including proton transfer from EC molecule to epoxy group producing hydroxyl group on carbon surface prior to the EC ring-opening reaction step. This work suggests that the presence of oxygenated functional group on anode carbon surface and solvent environment can have significant effects on EC decomposition mechanisms both thermodynamic and kinetic aspects. Including the electrolyte solvation shell is crucial for electrolyte decomposition investigation using molecular modeling.

Figure 1
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) Computational Design of Two-Dimensional Pentagonal Materials for Hydrogen Evolution Reaction
Authors: Zhuang Houlong , Liu Lei , Wang Duo
Published: May 2020

Two-dimensional (2D) materials such as MoS2 are promising for catalyzing the hydrogen evolution reaction (HER). Most of these 2D electrocatalysts exhibit hexagonal structures. We explore structure-property relationships to discover novel 2D electrocatalysts with the pentagonal structure that forms the so-called Cairo tessellation. We discover several 2D pentagonal materials that exhibit hydrogen binding energies that may lead to high HER catalytic ability. We also apply a continuum solvation model to study the solvation effects on the interactions between hydrogen atoms and a 2D pentagonal material. We expect this work to open up a new route of designing 2D catalysts for energy-related applications.
High Throughput Density Functional Investigations of the Stabilities, Electronic Structures of XYZ2 Compounds
Authors: Zhu Hong , Ke Liu , Xiaomeng Cai
Published: May 2020

The development of high-performance thermoelectric materials requires the reduction of the thermal conductivity as well as the enhancement of the power factor simultaneously, which may benefit from high-throughput materials simulations. Recently, we have revealed a new class of high-performance thermoelectric materials, namely XYZ2 (X,Y: rare earth or transition metals, Z: group VI element) based on high throughput simulations, among which TmAgTe2, YAgTe2, YCuTe2 have been successfully synthesized and proved to have extraordinary low thermal conductivity. But, similar to many other high-performance thermoelectric materials, e.g. PbTe, SnSe, XYZ2 thermoelectric materials could also have multiple phase transformations. Thus, it is important to systematically study the stability, electronic structure and transport property of different phases, and how these are related to the chemistry of the compound. The phase stabilities of XYZ2 compounds have been assessed by support vector machine methodology. We find that those compounds with larger X ionic radius have P3m1 space group with X ion in octahedral interstices, while smaller X ionic radius favors a tetrahedral site occupation with a space group of the compound of I-42d. Based on the gradient boosting algorithm, density of states effective mass mS* and fermi surface complexity factor NV*K* are identified as important descriptors to enhance zT values. Band structures and Crystal Orbital Hamilton Population analyses reveal that materials with larger mS* have a flat band to enhance Seebeck coefficient if the X-s (Y-d) orbitals have similar energy with Z-p orbital near the VBM. Cu and Ag based compounds with P3m1 space group are benefited from the Y-d orbital contribution to the high Fermi surface complexity factor. These intrinsic parameters including ionic size and molecular orbitals can alter stabilities and electronic properties, which provide us clues on how to design and improve the thermoelectric performance of XYZ2 compounds.
(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.
(Keynote) Design of Electrocatalysts at Atomic Scale
Authors: Stamenkovic Vojislav R. , Strmcnik Dusan , Lopes Pietro Papa , Markovic Nenad M , Lv Haifeng , Chung Dong Young , Wang Rongyue
Published: May 2020

In spite of large improvements in RDE, shaped nanoparticles do not exhibit substantial improvement in electrochemical devices, which requiresadditional steps in research aimed to development of more active nanoscale materials. The effect of nanoparticle size, surface mophology, composition and near-surface composition, shape, architecture, nature and porosity of the support will be thoroughly addressed. The main emphasis will be placed on the atomic precision approach that offers a new direction in the catalyst development. While hollow structures greatly diminish buried non-functional precious metal atoms, their uncommon geometry provides a pathway for tailoring physical and chemical properties. These structures can address some of the major design criteria for advanced nanoscale electrocatalysts, namely, high surface-to-volume ratio, 3D surface molecular accessibility, and optimal precious metal utilization, including durability and selectivity.
(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.
(Invited) High Catalytic Activity for Ethanol Bioelectrooxidation at Hybrid Electrocatalysts
Authors: De Andrade Adalgisa Rodrigues , Honorio Franco Jefferson , Minteer Shelley D.
Published: May 2020

The use of enzymes immobilized onto the surface of electrodes as the main catalyst in biological fuel cells has been extensively reported. A biofuel cell provides a means to obtain clean, renewable energy and have great potential to be used as alternative energy source for low power devices. There still a lot of important issues in the development of these device, one of them, is to obtain the maximum power density from the fuel for this is important to immobilize a group of enzymes to perform a cascade in order to maximize the fuel oxidation.

Recently, we have concentrated our goal to the develop hybrid nanomaterials with MWCNT in order to immobilize efficiently the enzymes and organic catalyst. We will report a number of approaches to combine enzymes with a recently developed TEMPO-modified linear poly(ethylenimine) (TEMPO-LPEI) coupled with carboxylate multi-walled carbon nanotubes (MWCNT-COOH) to transform ethanol, ethylene glycol into CO2. In the case of ethanol extraction of 12 electrons per molecule at a single hybrid anode has been obtained with success. This simple methodology can replace the use of enzymatic cascade (7-8 enzymes) and may improve the application in biofuel cells.

The electrochemical response of the enzyme system (MWCNT-COOH/LPEI/OxOx) at increasing concentrations of ethanol confirms the excellent activity of these hybrid bioanodes.

To confirm complete ethanol oxidation to CO2, electrolysis of ethanol was performed for using different electrode systems hybrid systems. Product analysis allowed us to correlate the increase in current with the formation of CO2 as main product. The modification of nanomaterials to obtain a large energy output form an enzymatic system will be highlighted.

Acknowledge: FAPESP (grants # 2017/20431-7 and 2014/50945-4 ), CNPq (grant (465571/2014-0) and CAPES 001. Army Research Office MURI (W911NF-14-1-0263).
Atomic Pt with Trapped Interstitial F in PtCo Nanosheets for Zinc-Air Batteries
Authors: Yang Yang
Published: May 2020

Platinum group metals (PGMs) based materials are currently dominantly used as oxygen reduction/evolution reaction (ORR/OER) catalysts in many emerging renewable energy devices such as Zn-air batteries (ZABs) because of their favorable surface electronic structures for electrocatalytic reactions. Most recently, atomic PGMs anchored on the conducting supports have been recognized as the most effective way to improve the utilization efficiency of PGMs and reduce the catalyst cost. However, traditional synthetic approaches to atomic catalysts, such as wet impregnation and atomic layer deposition, still have a long way to be optimized for industrial mass production. In this work, we designed a scalable and repeatable synthesis of atomic Pt in the alloyed platinum cobalt (PtCo) nanosheets by combining bottom-up electrodeposition and top-down fluorine-plasma (F-plasma) etching treatments. The interstitial F atoms trapped in the alloyed PtCo crystal structure induce lattice distortion which plays a crucial role in stabilizing the atomic Pt on the surface of catalyst (denotes as SA-PtCoF) by balancing surface free energy. Moreover, the proposed SA-PtCoF nanosheets are additive-free catalysts with abundant active sites and high surface areas, which show significant advantages over powder catalysts for ZAB due to the suppressed catalyst deactivations. Benefiting from the catalyst-support interactions and synergistic effects of SA-PtCoF, an unprecedented ZAB performance (power density of 125 mW cm-2, capacity of 808 mAh gZn
-1, cycle life over 240 h) is achieved, superior to commercial Pt/C@RuO2 and other state-of-the-art ORR/OER catalysts.
(Invited) Cobalt-Based Multicomponent Electrocatalyst Generated By Melamine Thermal Polycondensation
Authors: Alonso-Vante Nicolas , Zhong Haihong
Published: May 2020

The pivotal process and the bottleneck for electrochemical energy converting devices lies in the oxygen reduction reaction (ORR). The kinetics of this complex multi-electron charge transfer process is by two or more orders of the magnitude lower than the hydrogen reaction on Platinum. Intensive efforts have been devoted to develop earth-abundant metal elements-based materials, such as, Fe, Co, and Ni as possible alternates to Pt [1, 2]. Herein, our strategy was to develop a series of the cobalt-based electrocatalysts for ORR synthesized following various heat treatment of the chemical precursor supported on carbon Vulcan and melamine mixture. We observed that the cobalt-based active sites, nitrogen species and carbon carbonization/graphitization degree were different in the samples obtained from different annealing temperatures, which greatly influenced the electrocatalytic performances of these cobalt-based materials.

The ORR electro-catalytic performance (activity, stability and durability) were evaluated in alkaline medium. The sample annealed at 550 ˚C, showed a remarkable ORR activity, high stability, and long-term durability comparable with that of commercial 20wt% Pt/C catalyst, in alkaline medium.

Reference:

[1] H. H. Zhong, Y. Luo, S. He, P. Tang, D. Li, N. Alonso-Vante, Y. Feng, ACS Appl. Mater. Interfaces, 9, 2541 (2017).

[2] H. H. Zhong, R. Tian, X. Gong, D. Li, P. Tang, N. Alonso-Vante, Y. Feng, J. Power Sources, 361, 21 (2017).
(Keynote) Ellipsometric Study of a Molecularly Imprinted Polymer Modified Carbon Electrode for Detection of Hexahydrofarnesol
Authors: Stradiotto Nelson Ramos , Buffon Edervaldo , Huguenin Jose Augusto Oliveira , Da Silva Ladário , Carneiro Patrícia
Published: May 2020

Molecularly imprinted polymers (MIPs) are highly selective synthetic materials for the detection of target compounds. In this work, the spectroscopic ellipsometry was used to study the properties of a molecularly imprinted poly(ortho-phenylenediamine) film. This device was electrosynthesized by cyclic voltammetry on a glassy carbon electrode and applied for hexahydrofarnesol detection, which is the main contaminant of aviation biokerosene. The ellipsometric parameters were used to obtain the thickness of this polymeric film and the values found are in agreement with the atomic force microscopy data. Ellipsometric modeling was performed using Forouhi-Bloomer and Lorentz models, which are used to describe amorphous carbon films. Ellipsometric analyzes showed that the optical properties, including refractive index and extinction coefficient, as well as the dielectric constants of this molecularly imprinted polymer are sensitive to the presence or absence of the hexahydrofarnesol molecule. This confirmed the formation of the imprinted cavities after the extraction process of the template molecule. In addition, the dielectric constants showed that the formation of imprinted cavities leads to increased conductivity of the poly(ortho-phenylenediamine) film. The equilibrium parameters between the imprinted cavities and the hexahydrofarnesol molecules, such as the affinity constant and dissociation constant, were determined by the Langmuir adsorption isotherm to be 2.1×107 and 4.7×10-8 mol L-1, respectively. These values indicate that the imprinted cavities have a high affinity to recognize hexahydrofarnesol molecules. Under optimized conditions, the hexahydrofarnesol detection study showed that the MIP-modified electrode has two linear concentration ranges: 5.0×10-8 to 1.3×10-7 mol L-1 (y = 71C + 9.9×10-6; R2 = 0.973) and 3.0×10-7 to 1.5×10-6 mol L-1 (y = 2.6C + 1.9×10-5; R2 = 0.987). The presence of two linear ranges in electrochemically synthesized MIPs is due to the distribution of the imprinted cavities on the polymer structure. This behavior is in agreement with the ellipsometric studies, which pointed to a larger number of imprinted cavities on the non-homogeneous part of the polymer film. This study proved that spectroscopic ellipsometry is a powerful tool for the characterization of molecularly imprinted polymers.

Acknowledgments: The authors would like to thank Brazilian Agencies FAPESP (process 2017/23529-6), FINEP, CNPq, FAPERJ and CAPES for the financial support.
(Invited) Photo-Induced Signal Chains at Enzyme Electrodes
Authors: Riedel Marc , Lisdat Fred
Published: May 2020

During the last decade photoelectrochemical devices which couple biochemical reactions to light-sensitive electrodes have gained increasing research interest. These kind of light-triggered systems have the inherent advantage that an additional tool - the light - can be used to control the reactions at a sensing electrode. This allows a light-directed read-out, but can also be used to change the energetic situation on the surface resulting in advantageous potential behavior [1].

Enzymes as biocatalysts provide the advantage of a catalytic analyte conversion and specificity in this reaction. In order to couple them to light-sensitive electrodes different approaches have used.

Besides the use of co-substrates or products [2], we have been focusing on the use of mediators for this interaction [3] or the establishment of a direct electron transfer of the enzyme to the light- sensitive entity [4]. Here we report on the use of two different types of polymers for establishing the electrical contact.

In order to exploit the advantages of a high surface area we have constructed 3D electrodes which can be rather easily prepared by a template approach combined with spin coating as deposition method..Thus, the thickness of the electrode structure can be adjusted in a defined way [5,6].

In a first approach 3D TiO2 of inverse opal character has been sensitized by a conducting polymer – sulfonated polyaniline. The polymer has here two functions: It ensures the light sensitivity in the visible range and also provides an interface at which the enzyme can exchange electrons. Advantageously the current signal can be gained at rather low potential. Furthermore, the response can be tuned by the dimensions of the 3D electrode demonstrating the scalability of the approach.

As a further advancement we have used a redox polymer in order to couple FAD-dependent glucose dehydrogenase to the electrode. Here PbS QDs have been generated directly onto a 3D TiO2 electrode and characterized by TEM and photoelectrochemistry. The system allows the generation of a defined anodic photocurrent, which can be significantly enhanced by the biocatalytic conversion of glucose. Here the substrate dependent current signal starts at about -054V vs Ag/AgCl.

Such electrode systems can find application in light-triggered sensing, but also for bioenergetics since the photocatalytic process can be “feeded” by electrons from the biocatalytic conversion.

References

[1] F. Lisdat, D. Schäfer, A. Kapp, Anal. Bioanal. Chem. 405, 3739 (2013).

[2] J. Tanne, D. Schäfer, W. Khalid, W. J. Parak, F. Lisdat, Analytical Chemistry 83 (20) (2011) 7778–7785

[3] M. Riedel, N. Sabir, F. W. Scheller, W. J. Parak, F. Lisdat, Nanoscale 9, 2814 (2017).

[4] Ch. Stoll, S. Kudera, W.J. Parak, F. Lisdat,”,SMALL 2 (6) (2006) 741-743).

[5] M. Riedel, F. Lisdat, ACS Applied Materials & Interfaces, (2018), Vol. 10 (1), p. 267-277

[6] M. Riedel, W. Parak, A. Ruff, W. Schuhmann, F. Lisdat, ACS Catalysis, (2018), Vol. 8, 5212-5220
(Invited) New Ionic Liquids (ILs) for Secondary Batteries: Interplay between Structure, Electrical Response and Conductivity Mechanism
Authors: Vezzù Keti , Pagot Gioele , Negro Enrico , Di Noto Vito
Published: May 2020

The main bottleneck towards the development of high-performing “beyond Lithium ion” batteries in the portable electronic, electric automotive, and stationary applications [1] is the lack of electrolytes that are safe, electrochemically stable, and compatible with the electrode materials [2-3].

Recently published papers demonstrated that halo-aluminate ionic liquids (ILs) can provide an appealing alternative to conventional ethereal solvent-based electrolytes due to their low volatility, negligible flammability, and excellent electrochemical performance [4-7].

Following this, an overview on recent advancements on electrolytes for secondary batteries is presented, with a particular reference to imidazolium- and pyrrolidinium-based ILs. Insights on the interplay between thermal properties, structure and conductivity of BF4
-, Cl-/AlCl3, Cl-/TiCl4, and I-/AlI3-based systems are given, thus providing an in-depth understanding of the relation existing between ion speciation, long-range charge transfer mechanism, conductivity mechanisms and electrochemical performance of this very promising class of materials.

References

[1] B. Dunn, H. Kamath, J. M. Tarascon, Science 334 (2011) 928-935.

[2] V. Di Noto, T. A. Zawodzinski, A. M. Herring, G. A. Giffin, E. Negro, S. Lavina, Int. J. Hydrogen Energy 37 (2012) 6120-6131.

[3] B. Scrosati, J. Garche, J. Power Sources 195 (2010) 2419-2430.

[4] F. Bertasi, C. Hettige, F. Sepehr, X. Bogle, G. Pagot, K. Vezzù, E. Negro, S.J. Paddison, S.G. Greenbaum, M. Vittadello, V. Di Noto. ChemSusChem. 8 (2015) 3069-3076.

[5] F. Bertasi, F. Sepehr, G. Pagot, S.J. Paddison, V. Di Noto. Adv. Funct. Mater. 2016, 26, 4860-4865.

[6] F. Bertasi, K. Vezzù, G. Nawn, G. Pagot, V. Di Noto. Electrochim. Acta. 2016, 219, 152-162.

[7] G. Pagot, F. Bertasi, K. Vezzù, F. Sepehr, X. Luo, G. Nawn, E. Negro, S.J. Paddison, V. Di Noto. Electrochim. Acta. 2017, 246, 916-923.
(Invited) Polyoxometalate Electron-Coupled-Proton Buffers for Electrochemical and Photo-Electrochemical Water Splitting and Beyond
Authors: Symes Mark , Cronin Leroy , Chisholm Greig
Published: May 2020

The storage of renewably-generated energy as hydrogen via the electrolysis of water is a fundamental cornerstone of a sustainable hydrogen economy. Conventional electrolysers usually require stable power inputs in order to operate effectively and safely and so may be unsuited to harnessing renewable power, which is often intermittent and diffuse. Electrolysis mediated by Electron-Coupled-Proton Buffers (see, for example: Nature Chem.
2013, 5, 403-409; Science,
2014, 345, 1326-1330; J. Am. Chem. Soc.
2016, 138, 6707–6710; Joule, 2018, 2, 1390-1395) has the potential to overcome some of the challenges surrounding electrolysis using low and/or sporadic power inputs (especially those related to gas crossover) as the use of Electron-Coupled-Proton Buffers allows the oxygen and hydrogen evolution reactions to be completely decoupled from one another. In this talk, we shall investigate these claims for decoupled electrolysis (Electrochimica Acta, accepted for publication) and also explore the use of Electron-Coupled-Proton Buffers (ECPBs) as redox mediators in high energy-density redox flow batteries (Nature Chem.
2018, 10, 1042-1047) and for chemical hydrogenation reactions (Chem. Commun.
2018, 54, 1093-1096).

Figure 1
(Invited) Corrosion of PGM-Free Electrocatalysts for Oxygen Reduction in Fuel Cells: A Combined Experimental and Theoretical Study
Authors: Zhang Hanguang , Holby Edward F. , Martinez Ulises , Zelenay Piotr
Published: May 2020

Achieving practical stability and durability of PGM-free catalysts, e.g., M-N-C catalysts (where M, N, and C represent a transition metal, nitrogen, and carbon, respectively), remain a great challenge for the practical application of these catalysts in polymer electrolyte fuel cell (PEFC) cathodes. A variety of degradation paths have been proposed for M-N-C catalysts, including irreversible dissolution of the M from the active site and corrosion of the C matrix.1 Both mechanisms are active areas of research but it remains difficult to de-convolute contributions from each and how these mechanisms couple to environmental conditions (temperature, pH, fuel cell humidification, reactant flow rates, etc.). It is possible that metal dissolution occurs which destabilizes the local C which is then more easily corroded. It is also possible that C corrosion occurs which destabilizes the local M binding environment leading to dissolution of M. It is further possible that free radicals generated from 2-electron ORR pathways (either on M sites or defected-C sites) subsequently attack the C support, the M, or both. Also, the mechanisms may not be directly linked. Thus, without further understanding of each mechanism, it is difficult to prescribe methods of material stabilization or even accelerated stress tests for exacerbating a given activity loss mechanism.

In this talk, combined experimental and theoretical C corrosion studies of M-N-C catalysts will be presented. This work includes operando quantification of CO2 emission by nondispersive infrared detection and inductively coupled plasma measurement of metal dissolution as a function of fuel cell conditions. Specifically, the C corrosion of M-N-C catalysts will be evaluated at different relative humidity, cell temperature and reactant stoichiometry. M-N-C catalysts with various C structure will also be compared for exploring the possible mechanism of C corrosion in PGM-free catalysts. DFT calculations of C corrosion and oxidation as a function of atomic scale structure will also be discussed for comparison with metal dissolution stability studies. Overall, we aim to decouple de-metalation and C corrosion mechanisms for activity loss in PGM-free ORR electrocatalysts in order to better mitigate such losses, thus strengthening their case as PGM replacements in fuel cell applications.

References

1. Martinez, U., Komini Babu, S., Holby, E. F. & Zelenay, P. Durability challenges and perspective in the development of PGM-free electrocatalysts for the oxygen reduction reaction. Current Opinion in Electrochemistry
9, 224-232, 2018.
Graphene-Containing Metal-Organic Framework (MoFs) for Detecting Hydrogen Peroxide Produced By Cells
Authors: Guo Yemin , Sun Xia , Wang Guangxian
Published: May 2020

This study aimed to develop a nanoenzyme sensor that could detect hydrogen peroxide (H2O2) produced by cells. the graphdine materials were utilized due to its high specific surface area and good electrical conductivity additionly it could be loaded highly ordered porous materials of metal organic frameworks (MOFs). Due to the ability of the MoFs material to catalyze the oxidation of H2O2, the H2O2 produced by the cells was detected by amperometric method with the stimulation of the ascorbic acid. The electrochemical properties of the prepared graphdine-loaded MoFs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The high-sensitivity sensor was used to detect the content of H2O2 produced by living cells by amperometric method using a composite film of graphene@MoFs material to attach to the carbon fiber microelectrode .
Spherical MoS2/Carbon Composite with Improved Electrochemical Performance for Sodium-Ion Battery Anode
Authors: Lim Hyojun , Kim Hyeongwoo , Kim Sang-Ok , Choi Wonchang
Published: May 2020

Lithium-ion batteries (LIBs) with high energy density and long cycle life have been widely applied as the power sources in a variety of fields from portable electronic devices to large-scale energy storage systems (ESSs). Particularly in recent years, owing to the rapid growth of global electric vehicle and ESS markets, the cost of lithium source has risen sharply and many researchers predict a lithium shortage in the near future. In this regard, sodium-ion batteries (SIBs) have recently attracted growing attention because of low price and huge natural abundance of sodium, compared to lithium. However, the larger ionic radius of sodium ion (1.02 Å) than that of lithium (0.76 Å) results in poor electrochemical behaviors, which makes it difficult to find suitable anode materials for SIBs. [1] Among many proposed anode materials for SIBs, molybdenum disulfide (MoS2) is one of promising sodium-ion host materials because of its 2D-layered structure and high theoretical capacity of 670 mA h g-1. Despite these advantages, when used as an anode for SIBs, MoS2 exhibits several problems associated with low cycling stability and poor rate performance caused by large volume change during sodium insertion and extraction and low electrical conductivity. [2] In order to solve the aforementioned drawbacks of MoS2, herein, we present a spherical-shaped MoS2/carbon (MoS2/C) composite as a high-performance anode for SIBs. The spherical MoS2/C composites were synthesized by a facile and simple in situ wet chemical method using furfural as a surfactant as well as a carbon source. The as-prepared MoS2/C composite showed uniform distribution of MoS2 particles in the mesoporous carbonaceous matrix, which not only effectively alleviates large volume variation during repeated cycling, but also ensures high electrical conductivity. Owing to these benefits of good dispersion of active materials and the introduction of multifunctional matrix, the spherical MoS2/C composite electrodes demonstrated improved electrochemical performance such as enhanced cycle stability and superior rate capability. Furthermore, we believe that our facile and effective approach to synthesize MoS2/C composites can be extended to design and develop various transition metal-chalcogenides as promising and desirable anode candidates for SIBs.

REFERENCE

[1] Y. Xiao, S. H. Lee, Y. K. Sun, Adv. Energy Mater. 2017, 7, 1601329

[2] Q. Pan, Q. Zhang, F. Zheng, Y. Liu, Y. Li, X. Ou, X. Xiong, C. Yang, M. Liu, ACS Nano 2018, 12, 12578.

Figure 1