bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxygen Reduction Reaction Activity and Durability of Pt-Ni Catalysts Synthesized By a Continuous Flow Reactor
Authors: Fujine Keisuke , Wang Liang , Nagai Tomoyuki , Zhang Ying , Jia Hongfei
Published: May 2020

In recent years, polymer electrolyte membrane fuel cell (PEMFC) technology has attracted much attention and enabled the successful commercialization of fuel cell electric vehicles (FCEVs). However, the continuation of FCEV deployment still faces various hurdles, of which one major challenge is related to the high cost of platinum-based catalysts.[1] Substantial efforts have been dedicated for improving catalyst structure and composition to enhance their performance and thus lower the loadings for cost reduction. For example, shape-controlled catalysts such as octahedral PtNi and PtCo alloy nanoparticles showed much higher activity for oxygen reduction reaction (ORR) than the conventional Pt/C catalyst. [2-5] However, those advanced catalysts were typically prepared by batch synthesis with quantities often as little as a few milligrams, making it difficult for validation and further development of membrane electrode assembly (MEA) for commercial application. Attempt in increasing the catalyst amount by multiple batches can be time-consuming and sometimes challenging to maintain the consistency.

We recently designed a flow reactor (FR) to explore the continuous synthesis of Pt alloy nanoparticles (Fig. 1.) under elevated temperature and pressure (up to 350 °C and 1000 psi). It has several advantages including fast heat-exchange, fast mixing, uniform concentration and uniform temperature as compared to batch synthesis. These features made it possible to accurately control the reaction parameters to produce monodisperse Pt alloy catalysts up to 10 grams per day with high reproducibility. In this study, systematic investigation was conducted on the FR synthetic conditions for highly active catalyst. We were able to control the size and composition of resulting PtNi nanoparticles to achieve much higher ORR activity than commercial catalysts by optimizing synthesis conditions. As shown in Fig. 2 and Fig. 3, octahedral PtNi alloy catalysts synthesized by the FR showed much higher mass activity and specific activity compared to commercial benchmark. Attempts were also made to use machine learning tools to assist experimental design and data analysis for process optimization. It is expected that the combination of the latest development of data science and the inherent features of such flow reactors can substantially accelerate future FC catalyst R&D.

Figure 1
Doped-Graphene Based Electrocatalyst for Oxygen Reduction Reaction
Authors: Isopi Jacopo , Tuci Giulia , Giambastiani Giuliano , Marcaccio Massimo
Published: May 2020

The Oxygen Reduction Reaction (ORR) is a fundamental process for sustaining life as well as it is utilized in the field of energy conversion and biosensing analysis. The process, exploited in fuel cells and metal-air based batteries, proceeds at a very slow kinetic rate requiring a catalyst to reduce the activation barrier. Platinum is an ideal catalyst but it is neither cheap nor environmentally friendly. The prospect of an alternative to Platinum is intriguing and has yielded considerable research in the past decade. Amongst the most promising materials as catalysts, carbon-based systems, such as carbon nanotubes (CNT) and graphene derivatives, are particularly intriguing. Synthetic strategies allow to produce tunable graphene-based materials, starting from graphene oxide (GO) and reducing the oxidized groups of GO, in presence of compounds capable of adding functional groups or heteroatoms to the carbon lattice.

We were particularly interested in the material obtained by doping GO with nitrogen and boron through its reduction in presence of idrazine and borazine. Such doped reduced graphene oxides (rGO) show almost the same electronic properties as graphene, with some X-C (X= N or B) regions within the graphene lattice that have a useful dipole moment which helps the interaction between the oxygen molecule and the catalytic substrate; thus, such sites represent those active for the ORR catalysis. We report here the investigation of the electrochemical behavior of a selection of such material and their electrocatalytic activity for the ORR.
Electrochemical Evaluation of Rhus Vernicifera Biocathodes for Oxygen Reduction Reaction in Neutral Media with Application in Air-Breathing Hybrid Microfluidic Fuel Cells
Authors: Zamora-Suárez Andres , López-González Berenice , Cuevas-Muñiz Francisco Mherande
Published: May 2020

In this work, a Rhus vernicifera laccase electrodes (RvL-Vulcan/Toray and RvL-ABTS-Vulcan/Toray) were prepared by adsorption method and evaluated toward oxygen reduction reaction by cyclic voltammetry. The characterization was complemented by FTIR with ATR, these results indicates the presence of bands corresponding to the presence of enzymatic material for both electrodes and ABTS in the RvL-ABTS-Vulcan/Toray. The biocathodes were evaluated in an air-breathing microfluidic fuel cell reported previously by our group. For these experiments, a hybrid air-breathing microfluidic fuel cell configuration was constructed by an Au-Vulcan/Toray anode and 5 mM Glucose/0.3 M KOH as anolyte and the RvL-Vulcan/Toray and RvL-ABTS-Vulcan/Toray as biocathodes and PBS 7 as catholyte solution. The results showed that the RvL-ABTS-Vulcan/Toray 16 mWcm-2 performance was better than RvL 3.4 mWcm-2. This result it is attributed to the presence of ABTS in the material inmobilized.
Design of Optimized PEDOT-Based Electrodes for Enhancing Performance of Living Photovoltaics Based on Phototropic Bacteria
Authors: Reggente Melania , Politi Sara , Antonucci Alessandra , Tamburri Emanuela , Boghossian Ardemis Anoush
Published: May 2020

Living photovoltaics represent a growing class of microbial devices that are based on whole cell-electrode interactions [1-3]. The limited charge transfer at the cell-electrode interface represents a significant bottleneck in realizing an efficient technology [4]. This study focuses on the development of poly(3,4-ethylenedioxythiophene) (PEDOT)-based electrodes with enhanced charge transfer properties at the interface [5,6]. This is accomplished by the electrosynthesis of PEDOT layers from aqueous sodium dodecyl sulfate (SDS) solutions. Potentiodynamic and potentiostatic electrochemical techniques, as well as scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, and theoretical modelling of the electropolymerization transient, were employed to assembly and characterize PEDOT electrodes under various conditions. The produced electrodes are able to capture photosynthetically derived current under multiple light-dark cycles when interfaced with Synechocystis sp. PCC 6803. In the presence of the Synechocystis, the PEDOT electrodes show a six-fold and two-fold enhancement over conventional graphite electrodes for both mediatorless and K3Fe(CN)6 mediated conditions, respectively. The ability of these electrodes to enhance extracted photocurrent for both direct and indirect electron transfer mechanisms provides a versatile platform for improving various microbial devices.

[1] Zou, Y., Pisciotta, J., Billmyre, R. B., & Baskakov, I. V. (2009). Photosynthetic microbial fuel cells with positive light response. Biotechnology and Bioengineering, 104(5), 939-946.

[2] Pisciotta, J. M., Zou, Y., & Baskakov, I. V. (2010). Light-dependent electrogenic activity of cyanobacteria. PloS one, 5(5), e10821.

[3] Schuergers, N., Werlang, C., Ajo-Franklin, C. M., & Boghossian, A. A. (2017). A synthetic biology approach to engineering living photovoltaics. Energy & environmental science, 10(5), 1102-1115.

[4] Mouhib, M., Antonucci, A., Reggente, M., Amirjani, A., Gillen, A. J., & Boghossian, A. A. (2019). Enhancing bioelectricity generation in microbial fuel cells and biophotovoltaics using nanomaterials. Nano Research, 1-16.

[5] Tamburri, E., Orlanducci, S., Toschi, F., Terranova, M. L., & Passeri, D. (2009). Growth mechanisms, morphology, and electroactivity of PEDOT layers produced by electrochemical routes in aqueous medium. Synthetic metals, 159(5-6), 406-414.

[6] Zajdel, T. J., Baruch, M., Méhes, G., Stavrinidou, E., Berggren, M., Maharbiz, M. M., ... & Ajo-Franklin, C. M. (2018). PEDOT: PSS-based multilayer bacterial-composite films for bioelectronics. Scientific reports, 8(1), 15293.
Connecting Working Mechanisms of Micro Photosynthetic Power Cell with Photosynthesis and Respiration Processes
Authors: Tanneru Hemanth Kumar , Packirisamy Muthukumaran , Pillay Pragasen , Rengaswamy Raghunathan
Published: May 2020

Micro photosynthetic power cell (µPSC) is an electrochemical device that generates electricity by harnessing electrons and protons from the electron transport chains of photosynthesis (in the presence of light), and respiration (in the absence of light). µPSC is a potential power source for low and ultra-low power applications. The electron transport mechanisms to harness electrons are classified as direct and mediated. The mechanisms for working of µPSCs based on mediated electron transport are presented in literature. However, the impact of electrons being harnessed on the metabolic activities of the microorganisms has not been discussed in any significant detail. This work provides a theoretical analysis to address this lacunae by connecting the working mechanisms of µPSC to the processes of photosynthesis and respiration. Considering the production of one mole of glucose as a basis, the equations involved in the important steps of photosynthesis and respiration are developed. The developed equations are linked to the working mechanisms of µPSC. We propose that a µPSC can generate power, without inhibiting the micro-organism’s regular metabolic activities if excess water and carbon dioxide are available during photosynthesis and respiration in its anode chamber.
Metal Ions Influence on Shewanella Oneidensis MR-1 Adhesion to ITO Electrode and Enhancement Current Output
Authors: Alshahrani Aisha , Fitch Alanah , Al-Bazi John
Published: May 2020

The goal in this study is to enhance the eﬃciency of bacterial extracellular electron transfer (EET) in Shewanella.
oneidensis MR-1 by enhancing adhesion to the electrode. Our results clearly show a major difference in attachment and behavior of S. oneidensis MR-1 for Ca2+, Pb2+, Cd2+, and Mg2+
compared to the control. The final microbial coverage, as measured by confocal microscopy and cathodic peak charge in cyclic voltammetry (Qpc), increases with increasing metal ion concentrations. We found the cells attached to the electrode increased more with the addition of metal ion concentrations in the following order of metals: Ca2+ > Pb2+ > Cd2+ > Mg2+ compared to the control.

Riboflavin production and glucose consumption mirrored the same order as the electrochemical results.
Bioelectrochemical Microfluidic Platform for Cultivation and Integrated Characterization of Exoelectrogenic Biofilms
Authors: Rehnlund David , Klein Edina , Edel Miriam , Weiler Janek , Lim Guiyeoul , Sturm-Richter Katrin , Gescher Johannes
Published: May 2020

Microbial cultivation with the aid of microfluidic flow chambers has a great potential to form biofilms on an easy to handle laboratory scale. Our microfluidic cultivation platform with a modular design offers versatility and precision in terms of simulating different environments to study multiple growth conditions1. Thus, a long-term cultivation of biofilms can easily be obtained with the possibility of integrated on-line optical analysis. In this paper we will present our recent development of a bioelectrochemical microfluidic platform that allows cultivation and characterization of exoelectrogenic biofilms under anoxic conditions.

Electroactive biofilms will be cultivated and characterized in the microfluidic bioelectrochemical system focusing on electroactive microorganisms such as Shewanella oneidensis. The conductive intracellular protein chain of these microbes enables extracellular electron transfer (EET) from the cytoplasm through the cell membranes to an insoluble electron acceptor, such as an anode 2. Different deletion strains were cultivated and could be examined and compared with each other by chronoamperometry, electrochemical impedance spectroscopy, cyclic voltammetry and confocal laser scanning microscopy (CLSM). Genetically engineered strains focus on probing key genes that affect the biofilm forming properties of Shewanella oneidensis
3. In-situ fluorescence microscopy studies of biofilm formation and interaction will also be presented based on our modular microfluidic bioelectrochemical platform. We will also present our ongoing research on artificial electroactive biofilms that integrate electrodeposited nanostructures with a biocompatible hydrogel to form an artificial biofilm matrix.

In summary, electroactive biofilm growth under anoxic conditions using an anode as electron sink can be studied using our microfluidic flow technology. Examples of the versatility of the system as well as future outlooks on further biofilm growth conditions will be presented.

References

1. Hansen, S. H. et al. Machine-assisted cultivation and analysis of biofilms. Sci. Rep.
9, 8933 (2019).

2. Richter, K., Schicklberger, M. & Gescher, J. Dissimilatory Reduction of Extracellular Electron Acceptors in Anaerobic Respiration. Appl. Environ. Microbiol. 913–921 (2012). doi:10.1128/AEM.06803-11

3. Arinda, T. et al. Addition of Riboflavin-Coupled Magnetic Beads Increases Current Production in Bioelectrochemical Systems via the Increased Formation of Anode-Biofilms. Front. Microbiol.
10, 1–8 (2019).
Biological Fuel Cells
Authors: Safari Tahereh
Published: May 2020

A biofuel cell is a device that converts chemical energy into electrical energy through electro-biochemical reactions. In this type of cell, biocatalysts, which can be both enzymes and microorganisms or cells, are used to generate electrical energy. Biocatalysts are used in biofuel cells in two ways: 1) Biocatalysts can produce the fuel substrates required for fuel cells by biocatalytic reactions or metabolic processes.2) Biocatalysts can participate in the electron transport chain between the fuel substrate and the electrode surface. Accordingly, biofuel cells can be divided into two groups: microbial basic cells and enzymatic basic cells.

This article reviews the enzymatic fuel cell. These topics are reviewed:

1. Function of enzymatic biofuel cells

2. Investigation of methanol / oxygen enzymatic biofuel cell

3. Investigation of surface replacement of apoglucose oxidase on a gold electrode layered with PQQFAD

4. Investigation of bioelectrocatalytic cathodes made of cyt / cox

5. Examination of samples made of biodiesel based on enzymes layered by enzymes

6. Investigation of biofuel cell implants in animals
Development and Evaluation of Gel Fuel and Liquid Fuel Hybrid Structure of Fructose Fuel Cell
Authors: Yamakawa Atsuya , Todaka Keisuke , Imai Satomitu
Published: May 2020

An enzyme-type biofuel cell (EBFC) is a device that converts chemical energy into electrical energy by a redox reaction, using an enzyme as a catalyst to generate electricity. EBFCs have the features that it can operate at normal temperature, normal pressure, and neutrality. In addition, fuel can be selected depending on the type of enzyme, and the structure is simple and the easy to miniaturize. Therefore, EBFCs are expected to be a power source for medical and mobile devices. EBFCs have problems of low output and low lifetime. Hoshi et al. proposed using GCFC (large specific surface area) for the electrode, to improve the output [1]. EBFCs generally use oxygen in the cathode reaction. Therefore, oxygen supply is important in EBFCs. Kuroishi et al. reported on the improvement of output in air exposure type EBFCs using gel fuel [2]. However, the gel did not function well after a few minutes owing to drying i.e., they have a short lifetime. In this study, a new structure to solve these problems was proposed.

In this study, fructose was used as the fuel. Figure 1 shows the operating principle of EBFCs using enzymes of fructose dehydrogenase (FDH) and bilirubin oxidase (BOD). Figure 2 shows the hybrid structure of liquid fuel and gel fuel, which was proposed in this work. The electrode uses GCFC. The distance between the two electrodes and the thickness of the gel fuel is 3 mm. The specifications of the used enzyme, liquid fuel, and gel fuel are shown in Table 1. Figure 3 shows the cyclic voltammetry (CV) of the anode to determine the optimum concentration of the fuel (200 mM). Next, we compared the power density of a conventional gel fuel cell (original gel fuel cell) and a fuel cell with liquid fuel dropped on the cathode side of gel fuel cell (cathode wetting gel fuel cell). Figure 4 shows the power density of the original gel fuel cell and the cathode wetting gel fuel cell. The power density of the cathode wetting gel fuel cell is extremely reduced. This indicates that the gel fuel cell requires the cathode to be dry to provide sufficient oxygen. Therefore, the hybrid structure was adopted to make the gel dry on the side of cathode and to prevent the drying of the gel by contacting with the liquid fuel on the side of the anode. Figure 5 shows the power density of the three types of EBFC. The power density of the hybrid was 74.0 μW / cm2, which is almost equivalent to that of just using gel. Figure 6 shows the time history of the maximum power density. The gel fuel type halved power density after 45 minutes. However, the hybrid type achieved a power density of 61 μW/cm2, even after 120 minutes. This was the most important feature of this study. Figure 7 confirms that the high level of the maximum power density, even after 24 hours, was maintained to at least 62.3% (46.1 μW/cm2) of the initial value.

[1] K. Hoshi et al. Jpn. J. Appl. Phys, 55 02BE05,2016

[2] K. Kuroishi et al. IEICE Transactions on Electronics, pp151-154,2019

Figure 1
In-Situ TEM Observation of E-Beam Irradiation Induced Porous Molybdenum-Oxide Nanowires
Authors: Ting Yi-Hsin , Wu Min-Ci , Chen Jui-Yuan , Wu Wen-Wei
Published: May 2020

The Mo5O14-type structure is an important and representative to the MoO-based catalyst in the selective oxidation process. In the petrochemical industries, the MoO-based catalyst has been widely doped with other elements like V, Nb and Te to have distinct properties with high activity, selectivity and conversion efficiency. The specific facet and bonding relationship would affect the catalyst properties and functionality. The catalyst is usually synthesized as nanoparticles, which have random configuration and uniformity. Therefore, we successfully synthesized the single-crystalline Mo5O14 nanowires, which have uniform structure and controllability about diameter and length by CVD process. Besides, nanowire catalyst with nanoporous structure could possess both advantages of nanoparticles and nanowires. Therefore, we aimed at systematically analyzing Mo5O14 nanowires and then fabricating nanoporous structure in nanowires by e-beam irradiation. Utilizing advanced TEM techniques could reveal the overall atomic structure, which have intrinsic tunnel structure and unique periodicity. In addition, the e-beam irradiation on the intrinsic tunnel structure is observed by in-situ TEM. During the e-beam irradiation process, the oxygen atoms would be removed and result in the structure transformation. Using this technology, the irradiation region could be definable and controllable by electron beam size to define the distribution of nanoporous in nanowires. These results would benefit to realizing the catalytic selective oxidation related with Mo5O14-type structure but also fabricating nanoporous nanowires with rapid and convenient methods.

Figure 1
Understanding the Overcoated Catalyst Using in Situ Synchrotron X-Ray Techniques
Authors: Li Tao
Published: May 2020

Carbonaceous feeds, such as oil, gas, and coal, can be catalytically converted to useful products. Many of these reactions are conducted under harsh conditions, where the metal catalysts will rapidly sinter and lose activity. Overcoating is a methodology which preserves catalyst integrity under reaction conditions by depositing protective layers around the catalysts. Recently, we show that overcoating the metal nanoparticles with alumina using atomic layer deposition (ALD) will reduce the sintering and coking while the lifetime and reactivity of catalyst increase dramatically compared to the catalyst without ALD overcoating. It is believed that nano-sized pore (less than 2 nm) was formed during the calcination of ALD overlayer at high temperature. However, the mechanism of pore formation is still poorly understood due to the limited characterization technique.

Understanding the mechanism of the pore formation and further controlling the pore size are crucial for the development of the ALD overcoated catalyst. Recently, we demonstrated that small angle X-ray scattering (SAXS) can be used to characterize these ALD overcoated catalysts. From SAXS analysis, the thermal treatment resulted in the formation of ~ 3.5 nm pores. Moreover, the evolution of pore size was monitored by in situ SAXS technique. The pore size increases with increasing annealing temperature. In this proposal, we aim to investigate the mechanism of pore formation during the calcination using in situ SAXS as well as wide angle X-ray scattering, to understand how the ramping rate, gas used, nature of supports and overcoated materials affect the formation of the pore.
(Invited) Towards Theoretical Benchmarks on the Performance Capabilities of Pseudocapacitance
Authors: Bevan Kirk H , Foong Yee Wei
Published: May 2020

The efficient storage of energy in hybrid capacitors is based upon the co-optimization of both double-layer capacitance and pseudocapacitive (Faradic) charge storage. This inevitably involves a delicate balance of nano-structural and nano-porosity engineering, coupled with carefully designed electron transfer properties giving rise to pseudocapacitance. In this talk we explore how one might systematically tune the redox properties of nanoparticles to facilitate a near ideal pseudocapacitive response. Subsequently, we examine fundamental constraints on such nanoparticle derived pseudocapacitance and its implications for hybrid capacitors derived from nanostructured electrodes. The “battery like” Faradaic features of pseudocapacitance will also be discussed. In general this work is intended to provide benchmarks on the optimal performance capabilities of hybrid capacitors and their construction via nanoporous/nanostructured electrodes.
Selective Cation Transport through Graphene in Nafion | Graphene | Nafion Membranes
Authors: Bukola Saheed , Silva Liyanage Mayura , Creager Stephen E
Published: May 2020

Graphene and related two-dimensional (2D) materials are being intensively studied for use in membrane separators. The ultrathin nature of 2D materials combined with the opportunities they afford for intentional creation of nanometer-sized pores having controllable size and chemical character could allow for membrane separations with high flux and also high selectivity. Proton transport through graphene is especially interesting because it may occur through the intact pristine graphene rather than through defects / pores. Other cations, for example lithium or sodium, may pass through graphene but that transport is through to occur through defects / pores. This presentation will focus on selective cation transport through graphene layers that are embedded between Nafion membranes. Ion transmission through graphene is measured using a four-electrode cell in which two Luggin capillaries sense the potential difference that develops across the membrane in response to an ion current that is driven by a pair of platinum wire drive electrodes. Proton transmission in this cell configuration occurs more than 100 times faster than transport of any other ion. This difference is thought to reflect the different mechanisms by which protons and other cations pass though graphene. The lecture will discuss defect characterization in CVD graphene films, and will consider the role of defects, which are in fact nanopores, in allowing for selective transport of ions through graphene.
(Invited) Using Computational High-Throughput Screening and Machine Learning for the Data Design of High Performance Nanoporous Materials
Authors: Woo Tom Kwong , Boyd Peter George
Published: May 2020

Metal organic frameworks (MOFs) are a diverse class of materials built from organic and inorganic building units that can self assemble to form nanoporous frameworks. The hallmark feature of MOFs is the potential to tune the materials for any given application, which arises from the seemingly endless number of combinations of building units one can construct the materials from. To overcome this combinatorial design challenge we have developed a number of in silico screening tools and applied it to the development of new materials for gas separation processes such as post-combustion CO2 capture. First we have constructed a database of millions hypothetical materials using a novel structure spawning algorithm in which MOF structures can be generated from any topological periodic net (~1800 are experimentally known). Using molecular simulation techniques, we have screened the hypothetical materials for their gas adsorption properties, which provides the locations of the guest-host binding sites in each material. From the best performing materials, a similarity analysis was performed on over 100,000 binding sites to determine if the best performing materials share any common features in their binding sites. For the application of post-combustion CO2 capture, we found that two aromatic rings separated by 7.2 Ang provide an ideal, hydrophobic binding pocket that selectively adsorbs CO2. Our experimental collaborators were then able to synthesize 2 new MOFs with the targeted binding pockets and experimentally confirm that CO2 binds in them as predicted. To date these MOFs are amongst the best materials for selective CO2 capture under realistic humid combustion gas streams. Time permitting, we will also present how we have used deep learning models of nanoporous materials to rapidly predict the low-pressure adsorption properties of MOFs. Under these conditions, the chemistry of the pores is important and the geometric features such as the pore size, are not good predictors of the performance of the materials. Using a distance-between-features descriptor that accounts for the local chemistry of the materials, we have been able to develop accurate models that can predict the adsorption properties of nanoporous materials. Models were trained and tested on large, diverse databases of over 330,000 MOFs giving correlation R2 values on the test sets of >0.95, while geometric features provide R2 values of 0.71.
Fabrication of Nanoporous Metals through Thermal Decomposition of Transition Metal Dichalcogenides
Authors: Chatterjee Swarnendu , Li Yawei , Intikhab Saad , Snyder Joshua David
Published: May 2020

Nanoporous metals (np-M) owing to their high surface area-to-volume ratio and electrical/thermal conductivity, have emerged as promising materials for catalysis. There exists a group of processing methodologies by which np-M are formed through a top-down nanostructure evolution driven by the selective removal of a sacrificial component, all of which are a variation of dealloying. The driving force for the traditional electrochemical/chemical dealloying is difference of redox potentials and dissolution tendencies amongst the constituent metals. This limits the process to few noble metals e.g. Pt, Pd, Au etc. More recently liquid metal dealloying and vapor phase dealloying have shown success in mimicking the process of traditional dealloying based on difference of affinities of thermal dissolution in a liquid metal, and vapor pressures of the constituent metals, respectively. Nanoporosity evolution through current dealloying methodologies, however, is governed by strict requirements including sufficient separation in “reactivity” of the participating components and a homogeneous solid solution precursor alloy. This limits the viable alloy systems that may be used and the range of np-M's that may be formed with reasonable porosity length scales. Here, we report thermal decomposition of crystalline transition metal dichalcogenides (TMDs) as a new processing methodology for np-M formation, adding to the spectrum of dealloying protocols. We demonstrate application of this process to the formation of a broader class of np-M including W, Re, Mo, and Ta with feature sizes below 100 nm. The presented facile thermal treatment of TMDs offers a new methodology for the evolution of nanoporosity in a broad range of metals.
Nanoporous Aluminum for Solid-State Hydrogen Storage
Authors: Lee Timothy , Fu Jintao , Corsi John S , Detsi Eric
Published: May 2020

Effective hydrogen storage is still a challenge because the common approach to store hydrogen gas mechanically compressed in cylinders can be unsafe due to the high pressure and flammability risks involved. A promising alternative is solid-state hydrogen storage in lightweight materials. In this work, we explore ways to store hydrogen in ultrafine nanoporous aluminum during real-time fabrication of this nanoporous aluminum. Here I will present our novel scalable air-free synthesis method for ultrafine and oxide-free nanoporous aluminum with structure size in the range of 10-20 nm via selective electrolytic dealloying [1,2] and show how we extend this method to incorporate hydrogen in this nanoporous aluminum. Hydrogen can then be released by heating the material at moderate temperatures (~130°C). This method of hydrogen storage can find great use in on-board hydrogen storage for vehicular applications. [1] J.S. Corsi, J. Fu, Z. Wang, T. Lee, A. K. Ng, and E. Detsi: ACS Sustainable Chem. Eng. 7 (2019). [2] T. Lee, J. Fu, V. Basile, J. Corsi, Z. Wang, and E. Detsi: Under Review.
Template-Dewetted Au Nanoparticles on TiO2 Nanocavities for Photocatalytic Reduction and Scavenging of Hg(II)
Authors: Altomare Marco , Spanu Davide , Schmuki Patrik , Recchia Sandro
Published: May 2020

Anodically-grown arrays of TiO2 nanocavities[1] are used as substrate for solid state dewetting of Au thin films (≤ 20 nm-thick).[2,3] The resulting Au nanoparticle-decorated structures are explored as a photocatalytic platform for the reduction and scavenging of Hg(II) ions in aqueous solutions under solar illumination.[4]

The presence of the dewetted Au nanoparticles leads to a strong improvement of the photocatalytic Hg(II) reduction performance. Different reaction pathways are recognized for the Hg(II) abatement, which depend on parameters such as the Hg ion concentration, the Au nanoparticle size/loading, and the presence/absence of chloride ions and their concentration.

ICP-MS analysis of photocatalytically treated water streams confirms that under any experimental condition explored the removed Hg(II) is always accumulated on the photocatalyst surface.

Interestingly, in the presence of chlorides (to simulate contaminated sea water), and with relatively high Hg concentrations (10 ppm) and Au nanoparticle loadings (Au film initial thickness ~ 20 nm), a massive growth of calomel (Hg2Cl2) nanowires is observed. The nature of the photo-produced nanowires was confirmed by EDS and XPS analysis. The Hg2Cl2 nanowires nucleate at the surface of the Au nanoparticles, and their morphology (width, length, aspect-ratio) can be tuned by adjusting the Au nanoparticle size and illumination time.

On the other hand, in the absence of chlorides and/or at lower Hg(II) concentrations, Hg removal occurs via accumulation on the photocatalyst surface through the formation of AuHg alloy (amalgam) nanostructures.

Both mechanisms lead to an effective abatement of Hg: under solar light illumination, the scavenging process can lead to a Hg removal efficiency as high as 90% after 24 h. Regeneration of the Hg-loaded exhaust photocatalyst can be performed by photo-electrochemical anodic stripping, which converts the deposited Hg(0)/Hg(I) into soluble Hg(II), allowing for the accumulation of the scavenged Hg into small volumes of concentrated wastes. After four photocatalyst use/regeneration cycles, only a 10% decrease of activity was observed.

Besides the relevance of the photocatalytic results for water remediation technologies, our findings can also provide reliable nanostructuring tools for the templated synthesis of amalgam nanoparticles of tunable composition and size, or for the controlled growth of calomel nanowires for electro-analytical or sensing applications.

[1] J. E. Yoo, K. Lee, M. Altomare, E. Selli, P. Schmuki, Angew. Chemie Int. Ed.
2013, 52, 7514–7517.

[2] C. V. Thompson, Annu. Rev. Mater.
Res.
2012, 42, 399–434.

[3] M. Altomare, N. T. Nguyen, P. Schmuki, Chem. Sci.
2016, 7, 6865–6886.

[4] D. Spanu, A. Bestetti, H. Hildebrand, P. Schmuki, M. Altomare, S. Recchia, Photochem. Photobiol. Sci.
2019, 18, 1046–1055.
Improving the Stability of Lithium Metal By Porous Metal Oxide Coating
Authors: Kim Hohyeong , Lee Min Su , Yim Tai Hong , Jae-Young Park
Published: May 2020

Medium and large battery technology for energy storage devices or electric vehicles requires long life times and low cost as well as excellent safety. As a next generation high energy density type secondary battery, a lithium ion battery has been developed. However, when lithium metal cathodes is used, a redox reaction occurs at the interface between the electrode surface and the electrolyte, and lithium ions are eluted and lithium electrodeposits are concentrated. This phenomenon causes a problem that dendrite grows and causes an internal short circuit of the battery.

In this study, metal oxide nanoparticles were coated to form a porous layer on the surface of lithium metal for suppressing dendrite growth and interfacial transport of lithium ions during charging/discharging. The porous metal oxide coated Li metal unit cell showed an improvement of life times with maintaining the initial potential difference during charging/discharging.
Towards Structural Batteries Enabled By Fiber Reinforced Composites
Authors: Muralidharan Nitin , Westover Andrew S , Meng Chuanzhe , Pint Cary L.
Published: May 2020

The advent of electric automobiles has garnered great interest in multifunctional electrochemical energy storage architectures which have the potential to store and release energy on demand while simultaneously being subjected to static or dynamic load conditions. At the forefront of these technologies are energy storage integrated fiber reinforced composites which promise substantial benefits to both mechanical as well as electrochemical performance. In this context, the design of interfaces that dually store energy and maintain composite mechanical integrity under load is of critical importance. Here, I will illustrate our systematic efforts on the development of multifunctional structural energy storage composites starting with CNTs grown on lightweight stainless steel meshes and incorporation of these materials into energy storing composite laminates where we simultaneously test mechanical and electrochemical performance. To further augment the energy storing capability of the carbon nanotubes, we electro-deposit ultrafast redox active pseudocapacitive nickel oxide and iron oxide onto the CNTs to fabricate fiber reinforced nickel-iron asymmetric redox pseudocapacitiors or nickel-iron ‘ultra-battery’ composites. Overall, composites showcase high power densities of 10 kWh/kgActive and comparable energy densities of 20 Wh/kgActive. Furthermore, these multifunctional composites demonstrate good mechanical (tensile, flexural and load impact) behavior while simultaneously exhibiting stable charge/discharge performance during in-situ mechano-electrochemical measurements. These results thus forge a path toward practical multifunctional composites by combining (1) in-situ mechano-electrochemical testing to assess structural energy storage performance, (2) effective reinforcements and prevent failure at structural interfaces, and (3) redox-active materials processed to augment energy density. Overall, these results provide new insights and creates a framework for developing such multifunctional energy storage architectures for a multitude of load-bearing applications.

References:

[1] N. Muralidharan, A. Westover, et al., Carbon Nanotube Reinforced Structural Composite Supercapacitor, Sci. Rep. 8, 2018, 17662

[2] N. Muralidharan, et al., Multifunctional Structural Ultrabattery Composite, Nano Lett. 2018, 18, 7761-7768
(Invited) Quantum Mechanical Screening of Metal-N4-Functionalized Graphenes for Electrochemical Anodic Oxidation of Light Alkanes to Oxygenates
Authors: Cheng Mu-Jeng
Published: May 2020

Developing processes that allow partial oxidation of light alkanes (C1-C4) to more valuable oxygenates is important from both industrial and academic perspectives. In this study, quantum mechanics combined with a constant potential model were employed to evaluate the ability of metal-N4-functionalized graphene (gMN4) to catalyze anodic partial oxidation of light alkanes to oxygenates via electrochemical means while considering both the reactivity and selectivity. During the reaction, reactive oxo (*O) is generated through water electrochemical oxidation. This reactive oxo is used to oxidize light alkanes (represented by methane and propane). Based on investigating the systems with different Ms (Cr, Mn, Fe, Co, Ru, Rh, Os, and Ir) in a wide range of electrode potentials (U, 0.0 to 2.0 VSHE) and pH values (0.0 to 14.0), only gIrN4 and gFeN4 were capable of catalyzing this oxidation with acceptable reaction rates. The other catalysts were unable to form *O or inert to C-H bonds. Both alkanes can be oxidized but the rate for methane is slower. gIrN4 oxidizes methane to formaldehyde under proper Us. For propane, this catalyst generates iso-propanol at low Us and acetone at high Us. gFeN4 only oxidizes propane to acetone. Our theoretical investigation along with known experimental results suggest a high probability for experimental realization of this anodic partial oxidation, which would allow for utilization of natural gas discovered in remote oil fields.
(Invited) Multiscale Modeling of Formation and Properties of Solid-Electrolyte Interphases in Li-Ion Batteries
Authors: Bedrov Dmitry , Dong Dengpan , Ebrahiminia Mahsa
Published: May 2020

In this talk we will discuss recent efforts on multiscale modeling of solid-electrolyte interphase (SEI) and cathode-electrolyte interphases(CEI). The complexity and multiscale phenomena operating at electrode/electrolyte interfaces do not allow to access all necessary length and time scales using a single modeling approach. Combining information from high-level ab initio and DFT calculations, polarizable atomistic molecular dynamics simulations, coarse-grained implicit solvent simulations and continuum level modeling, we focus on understanding the mechanisms of formation of SEI/CEI layers, mechanisms of Li-ion transport, and mechanical and failure properties of SEI during charging/discharging processes.
(Invited) Structure Inference from X-Ray Absorption Spectroscopy Guided By Theory and Machine Learning
Authors: Lu Deyu
Published: May 2020

X-ray absorption spectroscopy (XAS) is a premier element-specific experimental technique for materials characterization in electrochemistry research. Specifically, X-ray absorption near edge structure (XANES) carries rich local structural and chemical information around X-ray absorbing species, which makes it a powerful tool to probe the dynamic evolution of the structural and electronic properties of materials during electrochemical processes. However, the correlation between XANES spectral features and the underlying local structural motifs and electronic properties is obscure, which often requires prior knowledge of fingerprints of known crystals to uncover. Here we show how first principles XAS simulations can be combined with data science to decipher the structure-spectrum relationship from XANES. We demonstrate how this approach can gain insights into the structural complexity of materials.
(Invited) Probing Electronic Transport Properties in Two-Dimensional Materials Using First Principles Calculations
Authors: Kuroda Marcelo A.
Published: May 2020

Heterostructures formed with two-dimensional (2D) materials preserve atomically sharp crystalline interfaces, offering novel platforms for a wide range of applications. Due to their one- to few-atom thickness, quantum mechanical effects and atomistic details play key roles in their properties. Here I will present the use of first principles calculations (density functional theory) to characterize and control electronic and spin transport in systems formed with these layered materials. First, I will describe the underlying mechanisms governing the contact resistance in lateral heterojunctions based on transition metal dichalcogenides (MX
2 with M = Mo or W and X = Se or Te). By joining semiconducting (2H) and metallic (1T') phases, these lateral structures have been proposed to improve charge carrier injection in these materials with respect to that obtained via direct deposition of metals [1,2]. We find that contact resistance values of < 10 W·cm may be achieved by enhancing the coupling between electrodes in lead and channel via phase engineering. Next, I will describe the features of the mechanical modulation of tunneling current (piezoresistivity) in vertical transition metal dichalcogenide heterostructures [3]. The piezoresistive effect measured in these systems is rationalized in terms of the electronic properties of the electrode (e.g. work function, d-bands, etc.), as well as the junction's thickness and composition. Finally, I will characterize the tunneling magnetoresistances in graphene/chromium trihalides heterostructures that were recently demonstrated experimentally [4]. Our description based on the ballistic transport evince the importance of quantum confinement and interlayer magnetic coupling emerging at these length scales [5]. In addition, our results show remarkable agreement with experimental measurements. The virtues and limitations of these approaches will also be discussed.

Acknowledgements: The author gratefully acknowledges the financial support from NSF DMR-1848344 grant.

References:

[1] R. Kappera et al., Nat. Mater. 13, 1128 (2014).

[2] S. Cho et al., Science 349, 625 (2015).

[3] D. Fu et al., Appl. Phys. Lett. 103, (2013).

[4] T. Song et al., Science 360, 1214 (2018).

[5] J. J. Heath et al., arXiv:1910.01102 (2019).
(Invited) First Principles Electron Transport Calculations: From Molecular Contacts to Large 2D Devices
Authors: Brandbyge Mads
Published: May 2020

The combination of Density Functional Theory (DFT) with non-equilibrium Greens functions (NEGF) allows for first principles calculations of electronic devices under working conditions, i.e. under the non-equilibrium conditions in the presence of finite electronic current[1]. I will show examples of how the DFT-NEGF method is used to gain insights into the non-equilibrium conduction and current-induced atomic forces in molecular contacts[2]. I will describe how we apply DFT-NEGF including electrostatic gating to study devices based on 2D materials[3,4]. Finally, I will present a recently developed multi-scale approach, combining spatial regions described by DFT with larger regions described by DFT-derived tight-binding. We have employed the multi-scale approach to study transport in molecular-based 2D graphene nanomesh structures going towards the (100 nm)-by-(100 nm) scale[5].

References:

[1] N. R. Papior, N. Lorente, T. Frederiksen, A. Garcia, M. Brandbyge, Comp. Phys. Comm., 212, 8, (2017). M. Brandbyge, J-L. Mozos, P. Ordejon, J. Taylor, K. Stokbro, Phys. Rev. B 65, 165401 (2002).

[2] J. Brand, S. Leitherer, N. R. Papior, N. Néel, Y. Lei, M. Brandbyge, J. Kröger, Nano Lett. 19, 7845 (2019); S. Leitherer, N. Papior, M. Brandbyge, Phys. Rev. B 100, 035414 (2019).

[3] N. R. Papior, T. Gunst, D. Stradi, M. Brandbyge, Phys. Chem. Chem. Phys., 18, 1025 (2016); Stradi, N. R. Papior, O. Hansen, M. Brandbyge, Nano Lett. 17, 2660 (2017); M. Palsgaard, T. Gunst, T. Markussen, K. S. Thygesen, M. Brandbyge, Nano Lett.,
18, 7275 (2018)

[4] N. Papior, G. Calogero, S. Leitherer, M. Brandbyge, Phys. Rev. B 100, 195417 (2019).

[5] G. Calogero, I. Alcón, N. Papior, A.-P. Jauho, M. Brandbyge, J. Am. Chem. Soc. 141, 33, 13081 (2019); G. Calogero, N. Papior, M. Koleini, M. H. L. Larsen, M. Brandbyge, Nanoscale 11, 6153 (2019); G. Calogero, N. R. Papior, B. Kretz, T. Frederiksen, A. Garcia-Lekue, M. Brandbyge, Nano Lett. 19, 576 (2019).
(Invited) Gold Nanoparticles for Key Reactions in Electrochemical Energy Conversion
Authors: Mayet Nolwenn , Rodal-Cedeira Sergio , Servat Karine , Kokoh Kouakou Boniface , Pastoriza-Santos Isabel , Pérez-Juste Jorge , Napporn Teko W.
Published: May 2020

Glucose oxidation (GOR) and oxygen reduction (ORR) are two intensively studied reactions for their concern in the development of sustainable energy sources. The oxidation of carbon monoxide (CO), considered as a poisoning reactant in organics conversion, is also a key reaction to be understood in electrocatalysis. Efficient catalysts should be designed for this purpose. Moreover, due to the surface reactions involved, the control of the catalysts' shape, size and structure is required to understand their activity and improve their stability. The outstanding properties exhibited by gold at nanoscale lead to various applications, including electrocatalysis which depends on the nanoparticles (NPs) surface structure and morphology [1]. Gold nanospheres (AuNSs) and pentatwinned gold nanorods (AuPTW NRs) were prepared by a revisited Turkevich synthesis and seed mediated methods respectively. Their surfaces were probed by the lead underpotential deposition (updPb) and the reduction of 4-mercaptobenzoic acid to reveal, respectively, the low and high index facets. The (100) facets of AuNSs are considered to be the active sites for glucose and CO oxidation in alkaline medium, while a AuPTW NRs@Pd core-shell material markedly promotes the ORR activity.

Figure 1
(Invited) Anodic TiO2 Nanotube Layers: Efficient Photocatalyst
Authors: Macak Jan M.
Published: May 2020

The self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 13 years motivated by their possible range of applications including photocatalysis, solar cells, hydrogen generation and biomedical uses [1,2]. The synthesis of these 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheet.

Among other TiO2 nanomaterials, these nanotube layers stand out due to their directionality, tunability of dimensions, ability to absorb significant amount of incident light and the possibility to utilize nanotube interiors and exteriors for decoration-coating of secondary materials.

One of the most significant applications of TiO2 nanomaterials is photocatalysis, which is very effective to decompose various pollutants (e.g. dyes) and kill bacteria [3,4].

The presentation will focus on the utilization of the nanotube layer for photocatalytic removal of various species in the liquid phase [5, 6] as well as gas phase [7]. We will also show that various secondary materials have a positive influence on photo-electrochemical properties of nanotube layers [8, 9]. Experimental details and some recent photocatalytic results will be presented and discussed.

References:

[1] J. M. Macak et al., Curr.
Opin. Solid State Mater.
Sci.,
2007, 1-2, 3.

[2] K. Lee et al., Chem. Rev., 2014, 114, 9385.

[3] K. Rajeshwar et al., J. Photochem. Photobiol. C: Photochem. Rev.
2008, 9, 171.

[4] Ch. Wei et al., Environ.Sci. Technol.
1994, 28, 934.

[5] J.M. Macak et al., Small, 2007, 3, 300.

[6] H. Sopha et al., Appl. Mater. Today,
2017, 9, 104.

[7] H. Sopha et al., Electrochem. Commun.,
2018, 97, 91.

[8] S. Ng et al., Adv. Mater. Interfaces
2017, 1701146.

[9] F. Dvorak et al., Appl. Mater. Today,
2019, 14, 1.