bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Nanosensors for Electrical Interrogation of Tissue and Cells
Authors: Cohen-Karni Tzahi , Rastogi Sahil , Kalmykov Anna , Garg Raghav , Lamprinakos Nicholas , Balakrishnan Gaurav
Published: February 2020

The interface between nanoscale electronic devices and biological systems enables interactions at length-scales natural to biology, maximizing communication between these two diverse yet complementary systems. Nanostructures and nanostructured substrates show enhanced coupling to artificial membranes, cells, and tissue. Such nano-bio interfaces offer better sensitivity and spatial resolution as compared to conventional planar structures. I will present the electrical properties of silicon nanowires (SiNWs) interfaced with embryonic chicken hearts and cultured cardiomyocytes. Utilizing the bottom-up approach enabled subcellular electrical recordings using the smallest reported device ever and thus exceeded the spatial and temporal resolution limits of other electrical recording techniques. I will discuss the synthetic breakthrough and novel fabrication required to realize the first new electronic measurement tool for intracellular measurements since patch-clamp of the 1970s – a truly three-dimensional nanoscale transistor. Finally, I will discuss my group’s current efforts to overcome the limits of cell-nanodevices interfaces. We are tackling these challenges through unique materials synthesis and device platform geometries. The exceptional synthetic control and flexible assembly of nanomaterials provides powerful tools for fundamental studies and applications in life science, and opens up the potential of merging active transistors with cells such that the distinction between nonliving and living systems is blurred.
(Invited) Solution Exfoilated Black Phosphorus and Its Applications
Authors: Lin Shenghuang , Lau Shu Ping
Published: February 2020

Black phosphorus (BP), has recently attracted much attention all over the world and shown great potential in novel nanoelectronics owing to its direct and narrow bandgap. Regarding to the scale production of BP and its related electronic devices, solution exfoliation reveals superior advances when compared with mechanical exfoliation. Remarkably, liquid-phase exfoliated BP flakes and quantum dots (QDs) exhibit exciting properties in solar cells, electronic, and optical devices. The exfoliation of BP in diverse solvents have been demonstrated. The solution exfoilated BP flakes can be an effective electron transport layer in organic photovotaics (OPVs). The BP QDs can be incorporated in the active layer of OPV to enhance its power conversion efficiencies. In addition, the BP flakes exhibit nonlinear opical properties which can be an excellent saturable absorber for high energy pulse generation in fiber laser.
(Invited) Recent Progress on 2D Materials for Electrochemistry
Authors: Chhowalla Manish
Published: February 2020

Over the past few years we have shown that chemically exfoliated 2D transition metal dichalcogenides (TMDs) are excellent for electrochemical applications such as energy storage and catalysis. For example, electrodes from restacked TMDs exhibit excellent volumetric capacitance along with high energy and power densities in energy storage devices. In this presentation, we will show that the high capacitance can be used for realizing ultra-strong electrochemical actuators. In addition to energy storage and actuation, we will describe new results on addressing key challenges involved in optimizing catalytic performance in TMDs. In particular, we will describe new strategies for optimizing the Tafel slope and current densities of various catalytic reactions using TMDs as catalysts. I will summarize the recent developments in 2D materials for electrochemistry, including our recent work on using reduced graphene oxide for oxygen reduction reaction, and discuss some challenges.
Molecular Motions, Structure, and Composition of Carbonates in the Solvation Shell of the Lithium Ion, Via Infrared Spectroscopies
Authors: Fulfer Kristen D'Ann , Kuroda Daniel G
Published: February 2020

A sustainable growth of the world population entails advanced energy storage technologies. In the last decades, many different energy storage technologies have been discovered and industrialized. While all commercial technologies rely on electrochemical reduction and oxidation of metals, the use of lithium has become the number one choice in batteries due to its high energy density. Even though lithium-ion technology has more than 10 years of commercialization, the charge density of current lithium-ion batteries is far from the theoretical limit. Currently, most technological and scientific efforts have been focused on the electrodes and little attention has been paid to the electrolyte. In particular, structure property relations of the electrolyte have not been derived because simple fundamental questions about the lithium ion solvation shell structure and composition have yet to be answered. Here, we present a study of lithium hexafluorophosphate salt (LiPF6) in pure carbonate solvents at commercial battery concentrations (i.e., 1 M). For this purpose, we used a combination of linear infrared (FTIR) and two-dimensional infrared (2DIR) spectroscopies supported with density functional theory (DFT) calculations. Our infrared experiments show the presence of two infrared bands in the carbonyl stretching region which are assigned to the lithium-coordinated and free carbonyl stretches. The 2DIR spectra of LiPF6 in either linear or cyclic carbonate solvents show the presence of a cross peak between the “free” and “coordinated” carbonyl stretches indicating a tetrahedral arrangement of linear carbonate molecules in the lithium solvation shell. Notably, 2DIR spectra also demonstrate that the lithium ion solvation shell is not a perfect tetrahedron. Ab-initio calculations confirm our assignments of the infrared bands. The 2DIR experiments also reveal that linear and cyclic carbonates have very different dynamics where the cyclic carbonates presents a much more ordered structure than its linear counterpart even as a pure solvent. Finally, our experiments demonstrate that simple structural modifications in the carbonates impact significantly the microscopic interactions of the system as seen from the formation of distinct ion pairs in the two carbonates. In summary, the contrasting differences observed in the structure, motions, and composition of the lithium ion solvation shell for the cyclic and the linear carbonates show new molecular information about carbonate-based lithium ion electrolytes.
Exploration of Novel Magnesium Battery Electrolytes based on Inorganic Salts
Authors: Hou Tianhong , Monroe Charles W
Published: February 2020

The theoretical volumetric capacity of Mg-ion batteries is far higher than state-of-the-art Li-ion batteries (3833mAh/cm3 for Mg vs. 850 mAh/cm3for Li). The development of suitable Mg-conductive electrolytic solutions has been a major barrier to Mg-ion technology: at present there is a need for liquids with wide anodic stability windows, whose interfaces allow plating and stripping of Mg with high coulombic efficiency and low deposition overpotential.

We have produced a number of Mg-conductive electrolytes by direct reaction of inorganic chloride salts with suspensions of Mg powder in nonaqueous solvents. The Mg-carrying cation in these electrolytes is presumably similar to the one that provides conductivity in the recently discovered magnesium aluminum chloride complex (MACC) electrolyte [1,2], but there is apparently no metal-complex anion, and no need for an auxiliary Lewis acid during synthesis.

The chemically synthesized Mg-conductive electrolyte formed by reacting ZnCl2 with Mg in tetrahydrofuran is stable up to 3.0 V vs. Mg/Mg2+, and produces an ionic conductivity of 0.24 mS/cm at room temperature. Cyclic voltammetry shows reversible Mg plating and stripping on platinum. The deposition overpotential of freshly synthesized electrolyte is below 200mV, and the coulombic efficiency of plating and stripping approaches 100%. Over a period of a week, the coulombic efficiency of plating/stripping only decays by 5%; the deposition overpotential increases more substantially with aging, however. Electrochemical Impedance Spectroscopy (EIS) was used to analyze the transport properties of the solutions. Other properties, such as composition and structure of electrolytic solutions, the morphology of Mg deposits, and thermal stability will be also discussed to explore the precise mechanism by which this and Mg electrolytes formed by other chloride salts form, as well as their feasibility for future magnesium battery applications.

Barile, Christopher J. et al. J. Phys. Chem. C 118.48 (2014): 27623-27630

Vardar, Gulin, et al.
 Chem. Mater. 28.21 (2016): 7629-7637

Figure 1
A Non-Linear Multi-Phase Field Model for Li Plating and Dendrite Growth at Li Metal Anode Incorporating Solid Electrolyte Interphase (SEI) Layer
Authors: Liu Zhe , Chen Lei , Qi Yue , Lu Peng , Chen Long-Qing
Published: February 2020

Despite the highest specific capacity and lowest voltage of all secondary Li battery anode candidates, the application of Li metal anode has been a challenge due to dendritic Li electrodeposition in liquid electrolytes, leading to battery degradation and even safety issues. We previously generated a dendritic pattern map using a non-linear phase field model for a Li metal/liquid electrolyte binary system. However, the solid electrolyte interphase (SEI), the key to understand the mechanism of Li dendrite formation, is not explicitly included in the model. In this study, we hereby further advance our phase field model by incorporating the effect of SEI layer (or any artificial electrode protective coating layers (PCLs)) as an additional phase. A new set of phase-fields are re-defined to distinguish the spatial distribution of each individual phase in the electrode/SEI/electrolyte microstructure. Butler-Volmer type non-linear electrochemical kinetics and the SEI phase rigid body translation are tested to validate the new model. The impacts of different SEI properties (e.g. conductivity, Li diffusion coefficient, electron tunneling range, etc.) on Li plating and dendrite formation will be investigated. The possibility of incorporating the SEI mechanical effects on Li plating will also be discussed.
Rate Limiting Effect of Charge Transfer during Lithiation from Ionic Liquids
Authors: F. Rodrigues Marco-Tulio , Lin Xinrong , Gullapalli Hemtej , Grinstaff Mark W , Ajayan Pulickel M
Published: February 2020

Room temperature ionic liquids have long been investigated as potential solvents to improve the safety of electrolytes used in Li-ion batteries. Despite the benefits conferred by their non-flammability and negligible volatility, these compounds often present limited electrochemical performance at high cycling rates, reducing the power output of the cell. Although the rate capability can benefit from an increase in ionic conductivity, the overall reaction kinetics also depend on the charge transfer at the electrode/electrolyte interface and on the solid-state diffusion of lithium ions in the host lattice. The contribution of each of these three processes to the lithiation kinetics of lithium titanate spinel are described, using an ionic liquid containing an alkoxy-modified phosphonium cation and the TFSI anion in the electrolyte. Based on the analysis of activation energies, the charge transfer was found to be the rate-limiting step for cell operation. This finding was further corroborated by the observation that a 50x decrease in charge-transfer resistance at high temperatures led to a dramatic performance improvement. Moreover, analysis of typical activation energy values reported in the literature for each of these processes indicates that charge transfer will very frequently determine the cycling rate when ionic liquids are used as electrolyte. We propose that charge-transfer resistance and electrolyte wetting on the electrode surface need to be explicitly considered when designing new ionic liquids electrolytes in order to equal or exceed the power density obtained with the use of current carbonate-based electrolytes.
In Situ Analysis of Solid Electrolyte Interface over Si Based Anodes Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy
Authors: Yohannes Yonas Beyene , Wu Nae-Lih , Lin Shawn D.
Published: February 2020

In lithium ion battery (LIB), silicon is hopeful electrode having a high theoretical capacity of 3579 mAh/g, which is ten times higher than the currently used graphite anode (1). On the other hand, Si-based electrodes suffer from the poor capacity retention due to the large volume changes during the lithium lithiation and delithiation process. The consequence of the volume change will lead to continuous decomposition of the electrolyte, which results in the formation of solid electrolyte interphase (SEI). Herein, the SEI formed based on fluoroethylene carbonate (FEC) electrolyte additive on a Si-based anode was investigated using in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), which have been also used to analyze SEI species on different electrodes (2, 3). The SEI generated on Si-based anode using 1 M LiPF6 in ethylene carbonate (EC) / ethyl methyl carbonate (EMC), 1/2 (v/v)/ vinylene carbonate (VC), (2 wt%) was started to observe at the onset of 1.1 V in the potential region of 1.0 – 1.3 V due to the decomposition of VC, which preferentially reduce prior to EC and EMC (4). Formation of poly (VC), polycarbonates, and Li2CO3 were identified during first cycle discharging. The incorporation of 10 wt% FEC results with the formation of poly (FEC)/(VC), polycarbonates, Li2CO3, alkoxy species and alkyl phosphorous fluorides. Using FEC as an additive with the onset potetial of 1.4 V the SEI formation started at a higher potential region of 1.3 – 2.5 V. In the course of second discharging, incorporation of FEC also impedes the decomposition of both solvent and salt anion reduction. Notable enough, in-situ DRIFTS spectrum due to the impact of FEC additive after five cycles also show the formation of SEI-film species is in fact increase in the lithiation process. DRIFT spectrum of the SEI-film formed over Si-based anode with and without FEC electrolyte at the onset potential is shown in Fig. 1.

Fig. 1 (a) The first cycle CV results of silicon-based electrodes with EC:EMC:VC/LiPF6 (black) and EC:EMC:VC + FEC/LiPF6 (blue). (b) DRIFT difference spectra obtained at the onset potential of silicon-based electrodes using (I) EC:EMC:VC/LiPF6 and (II) EC:EMC:VC + FEC/LiPF6based electrolytes.

References

1. C. C. Nguyen and B. L. Lucht, J. Electrochem. Soc., 161(2014).

2. A. M. Haregewoin, D. T. Shie, S. D. Lin, J. B. Hwang and M. F. Wang, Ecs Transactions, 53, 23 (2013).

3. M. Teshager, S. D. Lin, B. J. Hwang, F. M. Wang, S. Hy and A. Haregewoin, Chemelectrochem, 3, 337 (2016).

4. K. Tasaki, K. Kanda, T. Kobayashi, S. Nakamura and M. Ue, J. Electrochem. Soc., 153 (2006).

Figure 1
Evaluation of Electrolytes for Si-Based Negative Electrodes
Authors: Yang Li , Cai Mei , Lu Peng , Dai Fang , Xiao Qiangfeng , Verbrugge Mark W , Jiang Meng , Dadheech Gayatri , Ruthkosky Marty
Published: February 2020

In this work, different promising electrolyte salts, solvents and additives have been evaluated for nanosilicon (nano-Si) negative-electrode materials. For a wide range of solvents and salts used to formulate electrolytes, we found that fluoroethylene carbonate (FEC) is important for good Si electrode performance. The combination of FEC with dimethyl carbonate (DMC) gives the best electrochemical performance. We provide arguments to support our perspective that the superior solubility of the salts and FEC decomposition products in DMC leads to a more protective solidelectrolyte interphase (SEI). Consistent with this view, some SEI-forming precursors such as VC, LiBOB, LiODFB, if added in relatively large quantities (>2wt%), have deleterious effects on Si electrode performance due to competitive reactions with FEC decomposition, which, in the absence of such precursors, can form a more robust SEI on Si.

Figure 1
(Invited) Carbide/Nitride and Bimetallic Catalysts for Water Electrolysis
Authors: Chen Jingguang G
Published: February 2020

The high cost and impurity tolerance of Pt-group metal electrocatalysts used for HER and OER are significant challenges to overcome in order to achieve wide-spread electrolyzer use. Discovery of active, inexpensive, and impurity tolerant electrocatalysts should be guided by activity trends derived from density functional theory (DFT) calculations and experimental studies on well-characterized thin films. These trends then need to be extended to industrially relevant high surface area catalysts in order to bridge the materials gap.

In this talk we will use three examples to illustrate our efforts in reducing or replacing Pt-group metals for HER and OER. The first example is the utilization of monolayer (ML) Pt-group metals over transition metal carbide (TMC) substrates for HER in acid electrolyte. Metal-modified TMCs are promising inexpensive replacements for Pt-group metals because they have shown the ability to tune hydrogen binding energy, which is a descriptor for predicting the HER activity in acid. We will also use ML Pt-NbC thin films to compare the HER activity in acid and alkaline electrolytes, and to illustrate the impurity tolerance of Pt-NbC in the presence of tap water ions. The second example utilizes non-precious bimetallic catalysts for HER in alkaline electrolyte. The value of hydrogen binding energy appears to be a useful descriptor for predicting monometallic and bimetallic catalysts for HER in alkaline electrolyte. The last example shows the feasibility of coating monolayer coverages of IrO2 on transition metal nitrides for OER in acid electrolyte. All three examples demonstrate the importance of correlating theoretical calculations with experimental measurements for identifying alternative electrocatalysts for water electrolysis.
Highly Porous Molybdenum and Tungsten Carbides for Hydrogen Evolution Reaction Synthesized from a Sacrificial Leaching
Authors: Kim MinJoong , Song DongHoon , Oh SeKwon , Cho EunAe
Published: February 2020

Hydrogen has been considered as one of the most promising energy source for future due to its high-energy density and no air pollutant emission. Water electrolysis into hydrogen and oxygen is an environmentally friendly method to produce hydrogen. Water electrolysis reaction is divided into two half reactions; hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). High overpotential of both HER and OER is the most significant problems to hamper reaction rate and overall efficiency of water electrolysis, which leads to increase in hydrogen production cost. Therefore, exploring active catalysts for HER and OER is one of the major issues in water electrolysis. Platinum (Pt) has been conventionally used as an efficient catalyst for HER. But, its high cost and scarceness is not suitable for a large-scale application of water electrolysis. As for the HER, the electrocatalytic activities of carbide materials, such as molybdenum carbide (Mo2C), and tungsten carbide (WC), have been remarkable among non-precious metal based catalysts. But, it is very difficult to synthesize nanostructured carbides, which is regarded as a main obstacle for increase in HER activity of such carbide based catalyts.

Herein, we report highly porous Mo2C and WC catalysts synthesized from a sacrificial leaching for hydrogen evolution reaction. We firstly synthesized Mo2C and WC composites with cobalt nanoparticles (Co-Mo2C and Co-WC) using graphitic carbon nitride (g-C3N4) as a carbon source, and then leached Co nanoparticles in 0.5 M sulfuric acid (H2SO4) solution. Through this sacrificial leaching method, we could successfully synthesize highly porous Mo2C and WC nanoparticles. Highly porous Mo2C and WC catalysts exhibited much enhanced HER activities in hydrogen saturated 0.5 M H2SO4 solution in comparison to Mo2C and WC nanoparticles synthesized from conventional carburizing method.

Fig. HER activities of highly porous and conventional Mo2C nanoparticles.

Figure 1
An Efficient and Robust Surface-Modified Iron Electrode for Oxygen Evolution in Alkaline Media
Authors: Mitra Debanjan , Narayanan S. R.
Published: February 2020

The efficiency and cost of water electrolysis systems and rechargeable metal-air batteries can be improved by reducing the overpotential losses at the oxygen evolution electrode in alkaline medium. [1] Therefore, we seek inexpensive, efficient and durable electrocatalysts for the oxygen evolution reaction in alkaline medium. Transition metal oxides supported on nickel substrates have been the work-horse catalysts of industrial alkaline water electrolysis. But the cost added by nickel-based substrates can also be quite significant, and its replacement by less expensive materials is much desired. In our earlier study we had showed for the first-time that porous iron-sintered substrates modified by surface treatment using nickel can act as remarkably stable electrode when anodically polarized and also present a highly active electrocatalytic surface for the oxygen evolution reaction. [2] On these nickel modified sintered iron electrodes (NSI) we found an overpotential of 230 mV at 10 mA/cm2 (Figure 1 a).

In our quest for further improvements we have studied the effect of additive materials that can enhance the activity of NSI electrodes. Herein, we report a remarkably efficient and highly durable nickel modified iron electrode that has an iron sulfide additive (NSI-FeS) for oxygen evolution reaction. Such an electrode was prepared through a four-step process: (1) sintering of iron substrate along with 1 wt% of iron sulfide, (2) electrochemical oxidation of as-sintered electrode from open circuit potential to -0.6 V vs mercury-mercuric oxide electrode in 30 w/v % potassium hydroxide aqueous solution, (3) application of nickel coating and (4) calcination of nickel coating at 200o C. As-prepared NSI-FeS electrode exhibits an overpotential of ~200 mV to achieve 10 mA/cm2 current density with a Tafel slope of 46 mV/decade (Figure 1 a). The high activity for oxygen evolution may result from increased surface area obtained through electrochemical oxidation of iron substrate in presence of iron sulfide. The same electrode exhibits a highly stable overpotential for 1500 hours of testing at 10 mA/cm2 with an average change as small as 1 mV/1000 hour (Figure 1 b). Physical characterization methods such as XRD and XPS have been used to probe surface composition of the electrodes, and measurements for electrochemically active surface area were conducted through electrochemical impedance spectroscopy.

References:

[1] S. R. Narayan, A. K. Manohar and S. Mukerjee, Electrochem. Soc. Interface, 24.2 (2015): 65-69.

[2] D. Mitra, C. Yang, A. K. Manohar, P. Trinh, S .R. Narayanan, ECS Meeting Abstracts October 2016, No. 1, pp. 53-53.

Figure 1
An Alkaline Water Electrolyzer with Sustainion™ Membranes: 1 A/cm² at 1.9V with Base Metal Catalysts
Authors: Liu Zengcai , Sajjad Syed D. , Gao Yan , Kaczur Jerry , Masel Rich
Published: February 2020

This paper will consider the effects of catalyst composition on alkaline membrane electrolyzers with Sustainion™ membranes. In previous work1, 2we have demonstrated that Sustainion™ membranes are stable at 60 °C for at least 1500 hours in 1 M KOH. Here we compare a number of base metal catalysts on the performance of an alkaline water electrolyzer.

Figure 1 shows the voltage needed to maintain 1 A/cm2 in an alkaline water electrolyzer running at 60 °C in 1 M KOH. The blue circles in Figure 1 were taken with nickel nanoparticles on carbon paper on both anode and cathode. Initially we observed good performance, with a cell voltage of 2.1 V but the voltage increased by about 110 µV/hr over the 2000 hour run. The voltage needed to maintain 1 A/cm2 decreased to 2.05 V when NiFeCo was substituted for Ni on the cathode, but we still observed a voltage rise of 44 µV/hr. We stopped the runs after 2000 hours and found that the membrane was still fine, but the carbon paper on the anode was degrading. So we replaced the carbon paper with metal cloth. We also substituted NiFeOx for Ni on the anode. The voltage needed to maintain 1 A/cm2 dropped to 1.9 V, and was stable for 500 hours. The run is continuing.

It is useful to compare our results to those from the recent literature. The best previous alkaline water electrolyzers with base metal catalysts ran at currents below 0.25 A/cm² at 2 V3, 4 and even precious metal catalysts have had trouble maintaining 1 A/cm2 at under 2 V5, 6. These results show that alkaline water electrolyzers with Sustainion™ membranes and base metal catalysts show near precious metal performance.

[1]. Kutz, R., Q. Chen, H. Yang, S.D. Sajjad, Z. Liu, and R.I. Masel, Sustainion™ Imidazolium Functionalized Polymers for CO2 Electrolysis.Energy Technology, 2017to appear.

[2]. Masel, R.I., Z. Liu, and S. Sajjad, Anion Exchange Membrane Electrolyzers Showing 1 A/cm2 at Less Than 2 V. ECS Transactions, 2016. 75: p. 1143-1146.

[3]. Zeng, K. and D. Zhang, Recent progress in alkaline water electrolysis for hydrogen production and applications. Progress in Energy and Combustion Science, 2010. 36: p. 307-326.

[4]. Bodner, M., A. Hofer, and V. Hacker, H2 generation from alkaline electrolyzer. Wiley Interdisciplinary Reviews: Energy and Environment, 2015. 4: p. 365-381.

[5]. Ahn, S.H., S.J. Yoo, H.-J. Kim, D. Henkensmeier, S.W. Nam, S.-K. Kim, and J.H. Jang, Anion exchange membrane water electrolyzer with an ultra-low loading of Pt-decorated Ni electrocatalyst. Applied Catalysis B: Environmental, 2016. 180: p. 674-679.

[6]. Leng, Y., G. Chen, A.J. Mendoza, T.B. Tighe, M.A. Hickner, and C.-Y. Wang, Solid-State Water Electrolysis with an Alkaline Membrane. Journal of the American Chemical Society, 2012. 134: p. 9054-9057.

Figure 1
Corrole Chelated Metal Complexes for HER and Oer
Authors: Mahammed Atif , Gross Zeev
Published: February 2020

We have recently introduced corrole metal complexes (metallocorroles) as catalysts for various energy-relevant reactions. This includes those that are of prime importance for the electrochemical splitting of water into its elements, the hydrogen and oxygen evolution reactions. Tuning of the redox potentials, M(I)/M(II) for HER and M(III)/M(IV) for OER (M= Fe, Co, or Mn), is achieved via variations of substituents on the corrole ligand. These hypothesis-driven changes allow for the highly desired shifting of electrocatalytic onset potentials.

On top of the already published results listed below, new approaches and novel catalysts will be disclosed.

REFERENCES

“Cobalt Corrole Catalyst for Efficient Hydrogen Evolution Reaction from H2O under Ambient Conditions: Reactivity, Spectroscopy and DFT Calculations”, Inorg. Chem.
2013, 52, 3381-3387.

"The Cobalt Corrole Catalyzed Hydrogen Evolution Reaction: Surprising Electronic Effects and Characterization of Key Reaction Intermediates" Chem. Commun.
2014, 50, 2725-2727.

"Metallocorroles as photocatalysts for driving endergonic reactions, exemplified by bromide to bromine conversion", Angew. Chem.
2015, 54, 12370 –12373.

"Metallocorroles as Non-Precious Metal Catalysts for Oxygen Reduction", Angew. Chem.
2015
, 54, 14080 –14084.

“Metallocorroles as Non-Precious Metal Electrocatalysts for Highly Efficient Oxygen Reduction in Alkaline Media" ChemCatChem
2016, 8, 2832-2837.

“Metallocorroles as Electrocatalysts for the Oxygen Reduction Reaction (ORR)", Israel J. Chem.
2016, 56, 756– 762.

 “Dioxygen bound Cobalt Corroles”, Chem. Commun. 2017, in press.
Highly Efficient Water Splitting with Nickel Telluride: A Novel Bifunctional Electrocatalyst in Alkaline Medium
Authors: De Silva Umanga , Liyanage Wipula Priya Rasika , Masud Jahangir , Nath Manashi
Published: February 2020

The development of a highly active catalyst for water splitting to produce oxygen and hydrogen fuels is in rising demand to fulfill the increasing human need for clean and renewable energy. However, the most crucial step for efficient electrocatalytic water splitting is the oxygen evolution reaction (OER) that takes place at the anode. Traditionally, metal oxides have been introduced for this purpose however, recent developments have shown that transition metal selenides also shows better catalytic activity towards OER surpassing most of the conventional oxide electricatalysts. Herein we present how the family of chalcogenide electrocatalysts can be extended to transition metal tellurides and we will present the OER electrocatalytic activity of the first ever telluride, Ni3Te2 synthesized by hydrothermal reactions as well as electrodeposition technique. This catalyst show an overpotential of 170 mV at 10 mA/cm2 during the OER electrocatalytic activity in 1 M KOH, which is one of the lowest reported value till date and that highlight the high performance of this catalyst. Additionally, this catalyst also shows a high catalytic activity towards hydrogen evolution reaction (HER) and it only requires 250 mV over potential to achieve a current density of 10 mA/cm2 during HER conditions and that makes it a bifunctional elecrocatalyst. We will present the synthesis, characterization and electrochemical investigations of this new catalyst and additionally, we will also discuss the stability of this catalyst during long term OER conditions.
Performance of Pt-Ni Alloy Nanoparticles Supported on Carbon Nanotubes in Proton Exchange Membrane Fuel Cell
Authors: Cho Kuan Hsiu , Yeh Tsung-Kuang , Wang Mei-Ya
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) have attracted a lot of attention for alternative and green energy sources owning to their low-carbon emissions and high efficiencies. Pt-based electrocatalysts used in PEMFC electrodes are the main contributor to the high cost. More research focusing on the use of Pt group alloys is still required to achieve enhanced catalytic activity while decreasing the Pt loading. In this study, Pt-Ni binary catalysts by pulse electrodeposition and electroless-deposition process were developed for the enhancement of oxygen reduction reaction. The Pt-Ni catalysts were deposited on carbon nanotubes (CNTs) directly grown on carbon cloths. CNTs used for catalyst nanostructured supports can decrease the needs of Pt and improve the performance of fuel cells. The nickel nanoparticles were deposited on CNTs by pulse electro-planting to form large-area flake structures. Then the platinum nanoparticles were reduced on them in a potassium hydroxide solution containing platinum precursor and ethylene glycol at 75 oC for the deposition time of 3, 4, 5 hours. The sample with the commercial Pt/C and Pt/CNTs were also prepared for comparison. Structure and elementary composition of catalysts were measured by SEM, XRD and ICP-MS. Ni/CNTs sample showed a uniform distribution of Ni nanoparticles on the surface of CNTs, which was provided for the deposition of Pt nanoparticles with average particle size of about 5 nm. Electrochemical characteristics of PtNi/CNTs and Pt/CNTs samples were investigated via cyclic voltammetry (CV) analysis and rotating disk electrode (RDE) test in 0.1 M perchloric acid solution. In terms of both limiting current density and onset potential, the PtNi/CNTs samples were better than those of Pt/CNTs samples. All PtNi/CNTs samples with different Pt deposition time showed very similar LSV curves using RDE tests. In single cell test, the PtNi/CNTs, as the cathode catalyst, has a higher maximum power density (763 mW/cm2) than the commercial Pt/C. Among the PtNi/CNTs samples, the better performance of PtNi/CNTs sample with 4-hours Pt deposition time can be attributed to the more convenient Pt availability for the oxygen reduction reaction (ORR). It can be also found that the open circuit voltage of this sample could reach up to 1V due to a significant decrease of the polarization loss. The main outcome of this study was that Pt–Ni binary alloy catalysts had better oxygen reduction reaction for cathode of PEMFC.
Self-Diffusion of Nafion Ionomer in Confined Nanopores
Authors: Islam Muhammad Naoshad , Pilapil Brandy , Trifkovic Milana , Karan Kunal
Published: February 2020

Ordered nanoporous structures offer the advantage of high surface area and well-defined pathway for transport of charged and neutral species. Such structures with electronically conductive matrix are attractive option as alternative architecture for catalyst layers of polymer electrolyte fuel cells (PEFCs). However, the internal surface of these nanoporous material must be coated with sufficiently thin films of ionically conductive polymers (ionomers) while leaving pores still open for transport of reactants. One approach for achieving such thin films coatings is via self-diffusion of ionomers from its dispersion into the nanoporous structure. However, the efficacy of this process depends on various factors including the composition of the ionomer dispersion, which affects the aggregation state or shape/size of ionomer in the dispersion and the shape/size of the pores.

This work is concerned with the study of Nafion ionomer incorporation in model nanoporous structures with well-defined pore structure and size. A key challenge is quantification of the distribution of ionomer in these nanoporous structures. The thickness of ionomer films is anticipated to be a few nanometers, which limits the experimental observation to x-ray and electron microscopy based techniques both of which are known to damage polymers and also limit size of investigated volume of few tens of nanometers cubed. In this work, we have adopted laser scanning confocal fluorescence microscopy (LSCFM). The ionomer is first tagged with a fluophor. The tagged ionomer in dispersion diffuses through the pores of the nanoporous inorganic membranes of few tens of microns in thickness. The distribution of ionomer in the nanoporous membrane is mapped by LSCFM as function of pore size, ionomer concentration and exposure time. The figure below shows an example of Nafion ionomer distribution in anodized aluminum oxide nanoporous membrane.The results are cross-correlated with energy dispersive x-ray (EDX) characterization of selected samples. One of the peripheral questions, we wish to answer is whether Nafion ionomer can diffuse through sub-10 nm size pores that may exist in the secondary pores formed by aggregation of 30 nm Pt/C nanoparticle catalysts used for conventional catalyst layers of PEFCs. Furthermore, the methodology offers an attractive option for mapping long-range distribution of ionomer in tens of micron thick catalyst layers.

Figure 1
Preparation of PEMFC Electrodes from Milligram-Amount Catalysts
Authors: Yarlagadda Venkata , McKinney Samuel , Keary Cristin L , Thompson Levi T , Halevi Barr , Kongkanand Anusorn
Published: February 2020

Thin film rotating disk electrode (RDE) measurements have been commonly used for activity and stability measurements of catalysts for proton exchange membrane fuel cells (PEMFCs). However, many catalysts that exhibit excellent activity and stability in an RDE do not show acceptable performance in an actual fuel cell using a membrane electrode assembly (MEA). This could be due to differences in the measurement conditions and the stability of the catalysts. This shows the importance of measuring the activity and durability of catalyst materials using an MEA in an actual fuel cell. However, MEA electrode preparation traditionally involves ink making and coating, processes that commonly require a large amount of catalyst material (>1 g) in order to prepare a well performing MEA. This creates a significant challenge for catalyst development because in early stages only mg amount are usually available and up-scaling efforts can be expensive and time consuming.

In this study, we developed two techniques to fabricate fuel cell electrodes from a small amount of catalyst (ca 30 mg): one using vacuum filtration and one using ultrasonic spray coater. The electrodes can then be used to fabricate MEAs. The fabrication procedure, the characterization of electrode quality, and the electrochemical properties will be discussed in comparison to MEA prepared by a traditional ‘large-catalyst-quantity’ process. A recommended procedure for MEA fabrication from mg-quantity catalyst samples will be provided.

This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271.
A Highly Efficient and Stable Pt/Coo/CN Electrocatalyst Obtained Based on Metal Organic Framework for PEMFC
Authors: Guo Wei
Published: February 2020

A novel Co-based metal organic framework is synthesized in this study and used subsequently for the preparation of a Pt/CoO electrocatalyst with spherical structure. The catalyst prepared at 800 °C and the Pt co-doped into CoO nanoparticle surface to form a "Plum pudding" structure. This novel catalyst showed improved electrochemical performance and stability compared to commercial Pt/C catalyst.
Assessment of Hydrogen Peroxide Dismutation Rates: Detection of Oxygen and Peroxide on Se modified Pt Electrodes
Authors: Strobl Jonathan , Scherson Daniel
Published: February 2020

The heterogeneous dismutation of hydrogen peroxide (HDHP) in aqueous electrolytes is an important but rarely addressed process that can play a critical role in the analysis of the data for the oxygen reduction reaction (ORR). On this basis, it is essential to develop reliable experimental methods for determining its rates and their dependence on among other factors the composition of the electrolyte. A potentially powerful method to evaluate the activity of materials for the HDHP reaction introduced decades ago by Anson and coworkers [1] relies of the use of a ring disk electrode whereby the disk is made of the material to be examined and the ring is used to detect oxygen generated by the disk via the HDHP in peroxide containing solutions. As discussed in the aforementioned publication, the ring must be active for the ORR, but inactive for the reduction of hydrogen peroxide, i.e. a strict two-electron reducer. Such conditions were achieved in that work by employing a ring modified with a transition metal macrocycle found to display these rather stringent conditions. The strategy employed in our group, involves the use of a Se-modified Pt ring electrode and takes advantage of the ability of this surface to reduce rather exclusively dioxygen to peroxide demonstrated earlier in our group in efforts aimed at the development of an oxygen concentrator [2].

As shown in Figure 1, a Pt disk electrode covered by 0.34 ML of Se polarized at 0.175 V vs RHE in 0.5 M H2SO4 is capable of yielding mass transport limited currents for the 2-electron reduction of oxygen to hydrogen peroxide [2], as evidenced by the slope of the Levich plot for ORR. However, statistical analysis of these data indicated a small positive intercept. Additional experiments in which peroxide was intentionally added to the solution gave rise to a rather linear increase in the magnitude of the intercept with peroxide concentration, without changing the slope of the Levich plot. This interesting behavior suggests that although Se modified Pt is largely selective towards the 2 electron reduction of oxygen, hydrogen peroxide also yields a small amount of current via some unidentified reaction. Mechanistic investigations are currently underway, and the possibility of using this electrode for oxygen and peroxide detection is also under investigation.

References:

Shigehara, K.; Anson, F. C. J. Phys. Chem.
1982, 86, 2776 – 2783.

Mo, Y.; Scherson, D. A. J. Electrochem. Soc.
2003, 150, E39 – E46.

Figure 1
On the Experimental Investigation of the Clamping Pressure Effects on the Proton Exchange Membrane Water Electrolyser Cell Performance
Authors: Al Shakhshir Saher , Frensch Steffen , Kær Søren Knudsen
Published: February 2020

The intermittent renewable and power energy sources can be effectively utilized using hydrogen energy storage technology. Hydrogen has the highest energy capacity per unit weight of any known other fuel. Also it is considered as a promising energy carrier and a future replacement for fossil fuel energy sources. The proton exchange membrane water electrolyser (PEMWE) is the most candidate technology to produce hydrogen from renewable energy sources. PEMWE cell splits water into hydrogen and oxygen when an electric current is passed through it. Electrical current forces the positively charged ions to migrate to negatively charged cathode, where hydrogen is reduced. Meanwhile, oxygen is produced at the anode side electrode and escape as a gas with the circulating water.

In the recent few years, PEMWE’s R&D has inched towards; operating conditions; such as increased operating temperature and cathode-anode high differential pressure operation, flow field design, stack development, and modeling. In this work the effect of clamping pressure on the PEMWE cell performance is studied. A 50 cm2 active area PEMWE cell with double serpentine flow field channels for the anode and cathode side is used. The standard electrochemical technique to characterize the performance of electrochemical cells is the polarization curve. Thus, the IV curves are measured at different clamping pressures. Also, the electrochemical impedance spectroscopy (EIS) is used as a non-invasive technique to characterize the electrochemical processes at different clamping pressures. All these measurements are conducted at constant cell temperature (70°C) and atmospheric pressure. Furthermore, to ensure a high confidence level in the obtained data, experiments are repeated few times.

Early results for polarization curve predict that the PEMWE cell performance increases with increasing the clamping pressure at fixed temperature and current density. This can be elucidated by the EIS measurements which predict an increment in ohmic and activation resistance at lower clamping pressure values for the same temperature and current density.

Figure 1
Investigation on Nitridation Process of SrNbO2N Particles from SrNbO3 for Photoelectrochemical Water Splitting
Authors: Kodera Masanori , Seo Jeongsuk , Katayama Masao , Hisatomi Takashi , Minegishi Tsutomu , Domen Kazunari
Published: February 2020

Hydrogen produced from water using renewable energy has been investigated as a next-generation energy carrier. Photoelectrochemical (PEC) water splitting is a potential candidate for clean hydrogen production with reasonable cost. Considering utilization of sunlight as an energy source, photocatalysts need to absorb a wide range of visible light. SrNbO2N is an attractive material with an absorption edge of 690 nm and works as a photoanode in a PEC system.1 Photoelectrochemical properties of SrNbO2N particles are greatly affected by their oxide precursors and nitridation conditions. Therefore it is thought that understanding nitridation mechanism is a critical issue to activate PEC properties of oxynitrides. In this study, a novel oxide precursor SrNbO3 and subsequently nitrided SrNbO2N was investigated.

SrNbO3 oxide precursor was synthesized by a solid state reaction under an Ar flow.2 A mixture of Nb and Sr5Nb4O15 which was synthesized by calcining a stoichiometric mixture of SrCO3 and Nb2O5 in advance was heated under an Ar flow at 1773 K for 20 h. Obtained oxide precursors were nitrided under an ammonia flow at 1173 K for different time. Photoelectrodes of synthesized particles were fabricated by particle transfer method.3Nitridation process of oxide precursors were investigated based on X-ray diffraction, diffuse reflectance spectra and elemental analysis as which were combined oxygen-nitrogen analysis with inductively coupled plasma atomic emission spectroscopy (ICP-AES) as well as PEC properties.

SrNbO3 and SrNbO2N nitrided for more than 20 h both had a perovskite-type structure. At the initial stage of nitridation, however, SrNbO3 was separated to Sr5Nb4O15 and SrNbO3-x
N
y
then gradually nitrided to SrNbO2N as shown in Fig. 1. This phase separation appeared due to introduction of N atoms to oxidize Nb4+ to Nb5+. According to progression of nitridation, photocurrent densities improved. This study shows the effect of oxide precursor on the PEC performance of resulting oxynitrides. Nitridation mechanism affected by the crystal structure of oxide precursors is also discussed.

1) M. Kodera, H. Urabe, M. Katayama, T. Hisatomi, T. Minegishi and K. Domen, J. Mater. Chem. A, 2016, 4, 7658–7664.

2) X. Xu, C. Randorn, P. Efstathiou and J. T. Irvine, Nat. Mater., 2012, 11, 595–598.

3) T. Minegishi, N. Nishimura, J. Kubota and K. Domen, Chem. Sci., 2013, 4, 1120–1124.

Figure 1
(Invited) Catalysts and Interfaces for Hydrogen Production By Solar Photoelectrochemistry
Authors: Jaramillo Thomas F
Published: February 2020

The development of new, renewable pathways to produce the same kinds of fuels and chemicals that are conventionally derived from fossil resources, namely H2 and C-based products, could play a major role in reaching sustainability goals for the globe. This talk will focus on renewable fuels by solar photoelectrochemistry, with an emphasis on the development of electrocatalysts for hydrogen production and their integration onto semiconductors for efficient, stable operation. In particular, attention will be placed on non-precious metal catalyst materials combined with a broad range of semiconductors, including silicon, chalcopyrites, and III-V materials. In all cases, the non-precious metal catalyst systems can impart significantly improved catalytic activity as well as long-term stability.
Investigating the Plasmonic Hot-Carrier Injection Mechanism for CO2 Reduction Using Nanostructured Ag Catalysts
Authors: Kim Youngsang , Creel Erin , Corson Elizabeth , Qiu Fen , Urban Jeffrey J , McCloskey Bryan D , Kostecki Robert
Published: February 2020

Converting CO2 into hydrocarbons or other liquid fuels and leveraging solar energy to do so are of great importance as an alternative energy source and as a potential pathway to slow climate change. However, CO2 reduction reactions suffer from high overpotentials and poor selectivity. Recently, localized surface plasmon resonance (LSPR) was suggested as a way to overcome these challenging barriers [1-3]. Nanostructured catalysts absorbing visible light at their plasmon frequency can excite hot carriers which can be transferred directly or indirectly into the molecular orbitals of adsorbates. This unique charge injection mechanism along with the ability to tune the plasmon frequency over a wide range of energies may allow plasmonic photocatalysts to unlock a new, unexplored CO2 reduction pathway resulting in increased selectivity and lower overpotentials. Silver (Ag) is a strong plasmonic material and well-known for selectively producing CO [4,5]. In the hopes of taking advantage of the plasmonic properties to make more reduced products on Ag, we have developed Ag nanopyramid arrays, resulting in strong plasmonic and catalytic behaviors. Photocurrent measurements were performed on the plasmonic nanopyramid catalysts in aqueousNaClO4 saturated with either CO2 or Ar. The photocurrent is greatly enhanced in the presence of CO2, and shows ‘resonant-like’ behavior at a specific potential (-1.1 V vs. RHE). In Ar-saturated electrolyte, the photocurrent was drastically reduced and no characteristic feature of photocurrent was observed. This result indicates that the hot carriers created by LSPR react specifically with CO2 molecules or other CO2 reduction intermediates. By measuring incident photon to current efficiency (IPCE), we find that the hot-carrier transfer mechanism can be modulated as a function of applied potentials. Further, we discuss the differences in product distributions measured with a gas chromatograph (GC) and high performance liquid chromatography (HPLC) under light illumination and in the dark.

References

[1] A. O. Govorov, et. al., Nano Today 9, 85 (2014). [2] R. Sundararaman, et.al., Nature Comm. 5, 5788 (2014). [3] S. Mukherjee, et.al., J. Am. Chem. Soc. 136, 64 (2014). [4] R. Kostecki, et. al., J. Appl. Electrochem. 23, 567 (1993). [5] T. Hatsukade, et. al., Phys. Chem. Chem. Phys. 16, 13814 (2014).