bluuebunny/crossref_metadata_2025 huggingface dataset:
Designing and Fabrication of Low Cost Microfluidic Electrochemical Paper Analytical Device (ePAD) for Sensing
Authors: Kariate Sudhakaraprasad , Sonia Joseph
Published: May 2020

The development of electrochemical sensors as miniaturized and low-cost platforms for the rapid and sensitive detection of biomolecules demands for the requirement of disposable economically viable and easy manufacturable devices. Moreover, it should ASSURES (Affordable, Sensitive, Specific, User-friendly, Robust, Electrode for Sensing) the simple DIY (Do It Yourself) strategy. This could be achievable only if the substrate for the electrodes are inexpensive, easily manufacturable and should be from renewable and reusable resources. Simple paper offers unique advantages such as, easily printable, impregnable, and because of its innate cellulose structures, paper is protein and biomolecules friendly. In addition, porous structure acts as a good filter, and facilitates lateral flow. On the other hand, papers also have been used to make paper analytical devices (PAD), which have the advantages to incorporate microfluidic channels and reagent prestorage zones with mixing opportunities for colorimetric and electrochemical sensing units. Recently, these PADs have been recognized as low-cost and disposable sensing platforms.

Considering the aforementioned properties, herein paper has been explored as a substrate for the fabrication of microfluidic ePAD. Using simple photo-lithography technique, we could achieve the hydrophobic and hydrophilic regions for making a 3 in 1 electrode patterns consists of working, counter and reference electrodes along with the reservoirs for analyte of interests (sample inlet) and reagents (prestorage zones). The designed and fabricated ePAD with colorimetric detection zones (Fig.1) was further characterized by surface morphological and electrochemical studies. As a proof-of-concept, we were able to use ePAD as an electrochemical sensor for trolox (analogue of Vitamin E, an antioxidant), and a probe for selective detection of dopamine in the presence of ascorbic acid. On the other hand, the electrochemical investigations further revealed the interplay between edge plane sites, oxygen functionalities, and the carbon structures π-π interactions with pyrene conjugates towards biomolecules detection. The calibration plot for the trolox sensor showed linear range from 5 µM to 400 µM with a detection limit of (S/N=3) of 1.17 µM. The modified ePAD were able to detect dopamine in real sample with satisfactory results. Aforementioned observations indicated that ePAD have great potential to establish point-of-care testing platform for clinical applications. The findings also demonstrated simple fabrication of microfluidic ePAD is possible, unlike the widely used wax printing technique, and laser scribing or screen printing, or inkjet printing of electrodes onto different substrates, which requires sophisticated instrumentation and skilled personal.

Figure 1
The Change in Strain in Silicon Anodes Due to the Formation of the Solid Electrolyte Interphase
Authors: McBrayer Josefine , Serkland Darwin , Fenton Kyle R , Apblett Christopher A. , Minteer Shelley
Published: May 2020

Silicon anodes are a promising choice to replace graphite anodes in lithium ion batteries for electric vehicle applications because they have a near 10-fold increase in theoretical energy density. Unfortunately, the solid electrolyte interphase (SEI) on silicon has been found to degrade both mechanically and chemically. The strain due to SEI formation versus the strain in the electrode due to lithiation and delithiation is not well understood. This work used in situ moiré microscopy to make in-plane strain measurements with an emphasis on the observed strain during SEI formation. A novel method was used to create smooth, 50 nm silicon thin films on 2 µm thick copper foil electrodes. A sample grating was patterned on the backside of the electrodes for use with an in-house moiré microscope (see figure). The reference grating was incorporated into the microscope and imaged onto the sample to form moiré patterns which were then used to calculate in-plane strain. Strain measurements were obtained in situ with constant current cycling and cyclic voltammetry. Initial cycles show a greater strain response during the formation of the SEI. Special care was taken to try and deconvolute the different sources of strain. The changes in strain due to variations in temperature, electrolyte additives, and the introduction of electrolyte were explored.

Figure 1
Graphene-Wrapped Silicon Nanoparticles for All-Solid-State Lithium-Ion Batteries
Authors: Gad Mariam , She Zimin , Wilson Nicholas , Pope Michael A
Published: May 2020

Current lithium-ion batteries consist of a graphite anode and a metal oxide cathode. Due to their relatively high energy density and rechargeability, they have enabled various applications over the past few decades. However, significant improvements to battery cost, performance, and safety for applications such as vehicle electrification require a shift to next-generation materials, such as silicon as an anode which offers higher capacity, as well as solid-state electrolytes (SSEs) which are non-flammable. Both of these technologies currently suffer challenges which have prevented their widespread adoption. Silicon suffers low conductivity, and large volume change on each cycle, subsequently causing loss in electrical contact and the formation of an unstable solid electrolyte interface (SEI) each cycle. This project aims to solve these challenges by wrapping silicon nanoparticles and a sacrificial spacing material with crumpled graphene sheets using a scalable, spray drying method, and coupling it with a solid electrolyte. The graphene shell provides electrical contact with the silicon and space for its expansion during lithiation. The solid electrolyte provides a safer alternative to liquid electrolytes, and further reduces the SEI formation which, with a liquid electrolyte, can leak into such crumpled structures. In this work we will present our initial results concerning how the spacing material affects the structure and how the overall structure can be modified by spray drying parameters to determine optimal conditions for capacity and cycle-life using, first, at typical, organic carbonate-based electrolyte. We will explore different spacing material candidates such as chitosan which, upon heat treatment of the sample, would not only provide space for the expansion of silicon, but the residual nitrogen-doped carbon would also act as a conductive filler inside the crumpled structure. Furthermore, we will investigate various binder systems and their impact on cycle-stability including polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), sodium alginate (SA), and cross-linked SA. Based on preliminary, both PAA and SA are shown to have improved performance compared to PVDF as well as higher cycle life, however, SA forms smoother, thinner electrode films. Cross-linked SA is also shown to increase the cycling life and decrease the capacity loss per cycle. We then explore powder mixing and solution infiltration methods to introduce high conductivity SSEs and their performance when coupled to the graphene-wrapped silicon anode structures.
Geometry Optimization of Porous Electrode for Lithium-Ion Batteries
Authors: Deng Changyu , Lu Wei
Published: May 2020

Since the invention of lithium-ion batteries about 40 years ago, the electrodes have been manufactured in essentially the same way: granulating active materials into powder and pasting them on conductive substrate with some additives such as carbon black and binder. Most optimizations have been focusing on tuning parameters such as particle sizes, porosity and electrode thickness, with the assumption of a uniform electrode. Recently some work demonstrated better cell performance by engineering the shape of the electrode with features such as nano cylinders, tunnels and fractal branches. On the simulation side, however, to the best of our knowledge, there has been no report on freeform electrode shape optimization: all current shape optimizations assume a particular electrode pattern with a few adjustable dimensional parameters, and optimize those parameters. Here we report a method to optimize the topology of the porous electrode without a prior assumption of the pattern. An NMC 333 electrode with lithium metal as the counter electrode is considered as an example. To find the optimal solid material distribution for maximum specific energy, we represented the NMC material distribution by 5-by-5 nodal design variables. To solve this 25-dimensional optimization problem, we integrated Deep Neural Network (DNN) into Generalized Simulated Annealing (GSA). During the optimization process, the DNN learns the objective function in real time with training data generated from finite element calculations. GSA uses the DNN to iteratively calculate the optimal solution and generates new training samples based on current optimal geometry to provide feedback to better train the network for further refinement. We show that the method can produce an electrode pattern with the specific energy about 18% higher than that of the uniform electrode. This generic geometry optimization approach provides a powerful tool for the design and optimization of porous electrodes.

Figure 1
Chemo-Mechanical Model for Internal Stress Impact on Lithium Dendrite Growth
Authors: Meyer Julia Mae , Mukherjee Partha P. , Harrison Katharine Lee , Roberts Scott A.
Published: May 2020

Lithium-ion batteries have the potential for greater efficiency and lifetime than current commercial options. However, there are operational and safety concerns that must be addressed before expanding their applications. During charge-discharge cycles lithium dendrites form within the battery due to plating on Li-electrolyte surface inhomogeneities. Full penetration through the electrolyte to the cathode leads to a short-circuit, resulting in battery failure and sometimes fire. Thus, controlling the rate of lithium dendrite growth is imperative for creating safer and longer-lasting batteries. Dendrite growth occurs when the lithium deposition rate exceeds the stripping rate and increases when the current density at the peak of a surface inhomogeneity is greater than at the valley. Addition of mechanical stress due to both internal and external pressures can decrease the propensity for dendrite growth; for various system conditions, a critical pressure exists above which formation is suppressed. However, mechanical pressure also leads to other complications, including inhomogeneous transport through the separator caused by nonuniform contact of a rough Li surface. Pressure-driven creep of the Li surface additionally evolves the contact and mechanical landscape. In this work, we present a mesoscale model and parametrically study the effect of internal stress and material properties on dendrite growth. The model couples mechanical deformation in both Li and the separator with the electrochemical response during the charging phase. Both the effects of mechanical and transport properties of the liquid electrolyte are investigated. Phase maps of the conditions for which dendrite formation is encouraged or suppressed are created and can be used to inform battery manufacturing and material choices.

This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.
Impact of Water on the Properties of Litfsi-Acetonitrile Superconcentrated Electrolytes
Authors: Généreux Simon , Gariépy Valérie , Rochefort Dominic
Published: May 2020

Superconcentrated electrolytes are a new class of electrolyte that is of interest to the scientific community for battery applications. These electrolytes consist of an amount of salt greater than the amount of solvent, while remaining liquid. It is currently accepted that the reduction of the solvation sphere under these conditions results in a greater electrochemical stability of the solvent and a higher Li+ transport number. These properties are widely used in the literature For instance, superconcentrated electrolytes employing acetonitrile as the solvent have been applied in lithium metal batteries while acetonitrile with moderate salt concentration decomposes on lithium. Despite the attractiveness of the field to these electrolytes, their properties are still poorly understood, and the methods of analysis used vary between different studies. There is no standard protocol for their use and it becomes difficult to establish correlations between different studies. Our goal is to establish the required methods to standardize the methodology and fill the gaps in the field.

To do so, we firstly studied superconcentrated electrolytes based on LiTFSI and acetonitrile. The approach taken highlights the factors that have a significant impact on the properties of electrolytes. One of these factors is the water content. The results demonstrate that the presence of water in the solutions has a limited impact on the physical properties of viscosity and density of the mixtures as long at the concentration remains at and below 1000 ppm. The water content has a significant impact on the electrochemical window of stability of the electrolyte, reducing it to less than 2 V at 1000 ppm. The solvating structure of superconcentrated electrolytes is also studied via the electrochemistry of the Ferrocene/Ferrocenium couple to probe the impact of the electrolyte properties on electron transfer reactions. These results highlight the importance of structure and composition in the development of superconcentrated electrolytes.
Using Experiment and First-Principles to Assess Electrochemical Windows of Common Solid Electrolytes for Their Application in All Solid-State Lithium Batteries.
Authors: Benabed Yasmine , Rioux Maxime , Rousselot Steeve , Hautier Geoffroy , Dollé Mickael
Published: May 2020

During the last decades, lithium batteries have been developed to power a growing number of portable applications and to meet the needs of an increasingly mobile society. Their industrial and commercial application has always occurred in two successive steps of equal importance: the discovery of new electrode materials and/or electrolytes, followed by their extensive optimisation. A new generation of lithium batteries has been recently developed to meet high expectations in terms of safety, stability and capacity: All-Solid-State Lithium Batteries (ASSLB), where the conventional liquid electrolyte (LiPF6 + EC/DEC) is replaced by a safer and more stable ceramic, polymer or glass solid electrolyte (SE). ASSLB are partly developed with the prospect of using high potential materials as positive electrode and lithium metal as negative electrode. This is only possible through SE stated large electrochemical windows. Nevertheless, values for these electrochemical windows are very divergent in the literature published through the last decades. Recently, several studies have come to specifically decry the frequent overestimation of SE electrochemical stabilities 1,2. Establishing a robust procedure to determine SE real electrochemical windows has become detrimental. Our work is focused on developing a combined theoretical and experimental approach to better assess the electrochemical stability of widely used SE such as Li1.3Al0.3Ti1.7(PO4)3, Li1.5Al0.5Ti1.5(PO4)3 and LiLaTi2O6. In this presentation, we shed light on the importance of selecting the right experimental setup and explore the link between experimental and interpreted thermodynamic results.

1) Y. Tian, T. Shi, W. Richards, J. Li, J. Kim, S-H. Bo, G. Ceder. Energy Environ. Sci., 2017, 10, 1150

2)Z. Zhang, Y. Shao, B. Lotsch, Y-S. Hu, H. Li, J. Janek, L. Nazar, C-W. Nan, J. Maier, M. Armand, L. Chen. Energy Environ. Sci. 2018,11, 1945-1976.
Acetate-Based Water-in-Salt Electrolyte for Aqueous Sodium-Ion Batteries
Authors: Han Jin , Mariani Alessandro , Zarrabeitiaa Maider , Varzi Alberto , Passerini Stefano
Published: May 2020

Aqueous rechargeable alkali-ion batteries have attracted considerable interest in recent years due to reduced cost, lower environmental impact and, most importantly, and improved safety.1 Unfortunately, the narrow electrochemical stability window of water (1.23 V) limits the maximum output voltage of aqueous batteries, thus leading to intrinsically low energy density. Water-in-salt electrolytes (WiSE) constituted of, for example, highly concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solutions, has promoted the development of aqueous LIBs.2 However, these highly concentrated electrolytes based on fluorinated salts spoil the two major advantages of aqueous batteries, which are the low cost and reduced environmental impact.

Here we study alternative “Water-in-Salt” electrolytes (WiSE) based on highly concentrated sodium acetate and potassium acetate solutions. This kind of halide-free WiSE are studied by classical Molecular Dynamics (MD), evidencing the overall molecular arrangement to approach the “sponge-like” structure observed in certain ionic liquids and it offers wide electrochemical stability window and compatibility with stainless steel current collector. This is then employed as electrolyte in aqueous sodium-ion batteries featuring polyanionic compounds as active material. In-situ X-ray diffraction (XRD) experiments evidence the structural evolution during the reversible sodium de/intercalation. The X-ray photoemission spectroscopy (XPS) confirms the formation of a solid-electrolyte interphase (SEI) layer on the negative electrode. The cells show stable cycle performance and high coulombic efficiency above 99 % at 1C and 99.9% at 10C over 500 cycles.

Keywords: Acetate-based, Water-in-Salt electrolyte, aqueous sodium-ion batteries, high coulombic efficiency

References:

1. W. Li, J. R. Dahn, & D. S. Wainwright, Rechargeable lithium batteries with aqueous electrolytes, Science, 264((1994)1115-1118.

2. L. Suo, O. Borodin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang, K. Xu, "Water-in-salt" electrolyte enables high-voltage aqueous lithium-ion chemistries, Science, 350 (2015) 938-943.
Structure and Properties of Na-Se Alloys for Sodium Ion Battery: A First-Principles Study
Authors: Park Sungwon , Paek Eunsu
Published: May 2020

While selenium (Se) is recognized as a promising cathode material for sodium-ion battery (NIB), a fundamental understanding of the Na-Se electrochemical reactions upon sodiation is in its infancy. Based on density functional theory and ab initio molecular dynamics simulations, we evaluate single Na incorporation in the crystalline Se and also discuss the formation of Na-Se alloys in terms of structural evolution and energetics, along with their mechanical and diffusion properties. Our calculations clearly show that the inserted Na atom energetically prefers a heptagonal interstitial site, while cleaving the Se network bonds primarily due to the charge transfer from Na to the surrounding Se network. We also found that the inserted Na atoms undergo migration with low energy barrier of 0.16 (0.05) eV by jumping to adjacent heptagonal sites through intrachain (interchain) paths. When the Na content is sufficiently high, alloying between Na and Se becomes energetically favorable, as evidenced by the negative mixing enthalpy, with the most stable state obtained at 66 at.% of Na. We also found that increasing degree of sodiation leads to the disintegration of the chain-like bonded Se network into small chain. Lastly, we will address the influence of alloy composition on the diffusivity of Na and Se and mechanical properties in amorphous Na
n
Se.
Study of Mn(III) Disproportionation Reaction Using Vanadium and Titanium Additives: Application to Redox Flow Batteries
Authors: Reynard Danick , Maye Sunny , Peljo Pekka , Gentil Solène , Girault Hubert H.
Published: May 2020

Manganese, an earth-abundant transition metal, exists as Mn(III)/Mn(II) redox couple at a standard potential of +1.51V vs. SHE. It has drawn interest for implementation as positive side in V/Mn redox flow battery (RFB) due to higher achievable energy density than all-vanadium RFB. Unfortunately, Mn(III) disproportionation into Mn(II) and MnO2(s) led to loss of capacity, pressure drop increase and passivation of electrode surface during RFB cycling. We studied the influence of Ti(IV) or V(V) additives on Mn(III) stability in high acidic medium, by formulating 4 different electrolytes at equimolar ratio (Mn, Mn:Ti, Mn:V:Ti, Mn:V). Electrochemical characterizations reveals Mn(III) involvement in a complex nucleation/growth process at the electrode surface, along with its disproportionation. SEM combined to XPS demonstrates different oxide layers morphologies and chemical nature: MnO2 was formed in the presence of Mn and Mn:Ti, and MnO in the presence of V(V). Spectroelectrochemical study of Mn electrolytes highlights the displacement of the disproportionation reaction equilibrium in the presence of Ti(IV) or V(V) additives. Below 10% of electrolyzed Mn(III) was involved in the disproportionation reaction in the presence of Ti(IV) and V(V) (e.g., 25% without additives). V(V) was observed to enhance the stability of Mn(III) as compared to Ti(IV), which is of high interest for redox flow battery applications. In fact, Mn:V electrolyte could be used instead of Mn:Ti as the positive side of a Mn-V RFB will considerably reduce cross-contamination issues. As observed in the spectroelectrochemical study, the battery might be charged up to 90% SOC without loss of capacity. Moreover, in case of MnO particles formation, the strong acidic conditions will directly dissolve the particles preventing the battery from electrode passivation or/and pressure drop concerns.

Figure 1
A Numerical Investigation into the Relationship between Fluid Flow and Electrodeposition in a Silver Thermally Regenerative Ammonia Battery
Authors: Cross Nicholas R , Rau Matthew J , Hall Derek M. , Lvov Serguei N , Logan Bruce E.
Published: May 2020

As the need for a sharp reduction in carbon emissions continues to grow, many researchers are looking to electrochemical technologies to provide sustainable power to the grid. One promising technology is the silver thermally regenerative ammonia battery (Ag-TRAB), which takes advantage of low-grade waste heat (<100 °C) to create electrical power. Although the Ag-TRAB operates in a manner similar to a conventional flow battery, it is not charged by electrical power; instead the source of energy is (waste) heat. The Ag-TRAB uses silver as the active metal ion for deposition and dissolution on each half of the battery and porous carbon as the electrode material, driven by ammonia added into only one chamber. Following a discharge cycle, ammonia is removed using waste heat, and a new cycle is initiated using the ammonia added to the opposite electrolyte chamber. This technology can cycle hundreds of times without a decrease in performance, but its commercial implementation is currently limited by poor power and energy densities. In many electrodeposition technologies, porous flow-through electrode materials have been shown to have superior performance because of factors such as less dendrite growth and lower overpotentials. However, the relationship between the fluid flow and the deposition process within the porous electrode has not yet been investigated. As the Ag-TRAB is either charged or discharged, the deposition or dissolution of material can alter the porosity of the electrode, clog pores, and create preferential flow paths. Because the fluid flow directly governs convective mass transfer within the system, this flow evolution can have a substantial effect on performance. A numerical model was created using Comsol Multiphysics to study the relationship between fluid flow and electrodeposition in porous media. For each half-reaction, rotating disk electrode experiments were used to obtain the kinetic data for this specific chemistry. The impacts of porosity and Reynolds number on the mass transfer of the electroactive ions are presented. How these parameters affect electrodeposition uniformity, alter the flow through the electrode, and ultimately impact the peak performance of the cell is also discussed. It is shown that with increased porosity comes increased mass transfer as a result of reduced pore-clogging and increased unsteadiness within the fluid.
Andrzej Wieckowski: Forty-Two Years of Friendship
Authors: Zelenay Piotr
Published: May 2020

This special talk for me is dedicated to Andrzej Wieckowski, my long-time friend, mentor, and later partner in research, who we lost much too soon in the early 2019. This talk will be a combination of research in electrocatalysis we did together and reflection on a truly unique human being. It will be also a trip in time, spanning more than four decades and different places, from Poland in 1970s to the U.S. state of Oregon quite recently.
Surface Electrochemistry Decorated By Andrzej Wieckowski
Authors: Stamenkovic Vojislav R. , Markovic Nenad M , Strmcnik Dusan
Published: May 2020

Surface electrochemistry aimed towards materials with advanced catalytic processes will be thoroughly discussed in a view of footprint, contributions and approach that was pursued by Prof. Andrzej Wieckowski. A number of well-defined single crystalline surfaces will be brought to the audience to recall past time when many groups were focused on CO electrochemistry and design of new real world catalysts that would meet strict CO-tolerant requirements.

Andrzej was pioneering a difficult pathway in executing the most complex in-situ measurements and he was always challenging others in order to push the field towards new frontiers. That time created a number of highly visible articles and research groups were competing who would be the first in proposing the new reaction mechanism, novel material or to dispute work of others who made questionable claims. That time is known as golden era of electrochemistry, where scientific knowledge did not have alternative in front highly critical audience. This field is missing those times, and for that reason, this symposium is an outstanding opportunity to recall past, and to remember Prof. Wieckowski as a pillar who was setting the new limits.
Identification of Active Species and Mechanisms in Non-Precious Metal Oxygen Reduction Catalysts By Poisoning and Magnetic Measurements
Authors: Gewirth Andrew A. , Esposito Anne Marie
Published: May 2020

This talk addresses the Oxygen Reduction Reaction (ORR) utilizing Fe- and Co-based non precious metal (NPM) catalysts. There has long been uncertainty as to the active site for ORR in these materials due to the heterogeneity of the as-prepared catalyst. We have developed several methods with which to interrogate these materials. First, by using a purification scheme which removes and then remetallates the active site we substantially reduce catalyst heterogeneity. Second, we have developed a method by which to poison some of these active sites. Third, we use magnetic measurements to probe those sites affected by poisoning. We show as well that there is a minimum metal requirement for high ORR activity and that the metal must be arranged in certain critical configurations.
Detection of Intermediate in Ammonia Oxidation Reaction Using Aggregation-Induced Emission Phenomenon
Authors: Siddharth Kumar , Alam Parvej , Tang Ben Zhong , Shao Minhua
Published: May 2020

Ammonia electro-oxidation reaction (AOR) is a vital reaction for solving energy and environment problems as it is the anodic reaction in direct ammonia fuel cells (DAFCs), ammonia electrolyzer and in the remediation of wastewater containing ammonia.1-2 Designing high-performance electrocatalysts for AOR requires thorough understanding of mechanism and intermediates produced. Techniques like in-situ FTIR have provided information about intermediates produced during AOR in aqueous alkaline media.3-4 However, the mechanism is still not well understood and more proof of exact intermediates are needed. Furthermore, these in-situ methods are complex with multiple procedures requiring extreme precision.

N2Hx is an important intermediate in the dimerization step according to Gerischer and Mauerer mechanism. In this work, aggregation-induced emission (AIE) phenomenon was used for the first time to target and detect hydrazine (N2H4) as an intermediate during AOR using commercial Pt/C as electrocatalyst. Tetraphenylethene-CHO (TPE-CHO) molecule as AIEgen was used for this purpose. Combination of photoluminescence (PL) spectra showing turn-off fluorescence along with the electrochemistry results illustrated the presence of hydrazine as an intermediate. In Figure 1, fluorescence spectra in THF/water mixture with 90% of water fractions for different electrocatalyst loading keeping the AIE concentration same is depicted. It was observed that with increase in catalyst concentration, PL spectra intensity decreased considerably indicating towards the desired reaction of intermediate produced during reaction with the already present AIE on GC electrode.

Control experiments using graphene and TPE were performed to elucidate the results further. Mass spectra of the product formed after reaction between hydrazine hydrate and TPE-CHO was obtained and compared with the one obtained during electrochemical reaction. A very simple and novel method for detection of an intermediate, hydrazine in AOR using AIE phenomenon is demonstrated opening new strategy for mechanism understanding of an electrochemical reaction.

Figure 1. Fluorescence spectra in THF/water mixture with 90% of water fractions for different electrocatalyst loading keeping the AIE concentration same.

References

1. Zhong, C., Hu ,W. B., and Cheng Y. F., Journal of Materials Chemistry A
2013, 10, 3216-3238.

2. Siddharth, Kumar, Yattung Chan, Lu Wang, and Minhua Shao, Current Opinion in Electrochemistry
2018, Vol 9, 151-157.

3. Matsui, T., Suzuki, S., Katayama, Y., Yamauchi, K., Okanishi, T., Muroyama, H., and Eguchi, K. Langmuir
2015, 31, 11717-11723.

4. Katayama, Y., Okanishi, T., Muroyama, H., Matsui, T., and Eguchi, K., ACS Catalysis
2016, 3, 2026-2034.

Figure 1
Catalytic Performance Study of Ptni-Nanowires for the Oxygen Reduction Reaction (ORR) with Temperature-Controlled Experiments in Alkaline Medium
Authors: Soto Perez Joesene J. , Cabrera Carlos R
Published: May 2020

Fuel cells (FC) are emerging technologies that will eventually sustain energy demands replacing fossil fuels. However, the Oxygen reduction reaction (ORR) behaves sluggishly in acidic medium, were actual commercialization of FC concentrates. An alternative is to use alkaline environment were the ORR have demonstrated great activity using non-precious metals, replacing the more frequent catalyst, Pt/C. In this study we focused our interests in PtNi-nanowires (NWs), based on the promotive results that Ni offers to Pt. Additionally the addition of Ni will lower the cost of the catalyst. Preliminary results demonstrated current densities of 4.5 mA/cm2 with an E1/2 = 0.817 V for the PtNi-NWs in alkaline medium at (25.00 ± 0.01) °C. Additionally, the number of electrons was calculated using the Koutecký-Levich analysis with and without temperature-controlled instrumentation resulting in n= 3.79 ± 0.05 and n=3.99 ± 0.05, respectively. Moreover, durability experiments demonstrated that the PtNi-NWs maintained optimal catalytic activity for ORR along 10,000 cycles. The initial reported E1/2 was of 0.817 V and after 10,000 cycles E1/2 = 0.812 V, this represents a remarkable 5mV change in the E1/2. The results presented here suggest that PtNi-NWs is a sustainable catalyst for the ORR in alkaline medium and that it can be consider for future Anion Exchange Membrane Fuel Cells (AEMFCs) studies.
Pdni Nanocubes As a Highly Active Electrocatalyst for the Ethylene Glycol Electro-Oxidation Reaction
Authors: López-Coronel Andrés , Bañuelos Jennifer A. , Galindo de la Rosa Juan de Dios , Álvarez-Contreras Lorena , Guerra-Balcázar Minerva , Arjona Noé
Published: May 2020

In this work, Pd nanocubes and PdNi bimetallic nanocubes were obtained using NaBr as directing agent and polyvinylpyrrolidone as stabilizer in an aqueous reduction method. According to high-resolution transmission electron micrographs (HR-TEM), monometallic Pd nanocubes with sizes of 10 ± 0.5 nm and bimetallic PdNi nanocubes with sizes of 7 ± 1 nm were obtained. X-ray diffractograms displayed crystallographic peaks attributed only to Pd, finding crystalline sizes close to the particle size values. Electrocatalytic evaluation of these materials for the ethylene glycol electro-oxidation reaction (EGOR) was performed varying the KOH and EG concentration, the operating temperature and scan rate. PdNi nanocubes displayed at 1.5 M KOH and 1 M EG a maximum current density (jp) of 110 mA cm-2, while this jp increased 2 times at 50°C. Pd nanocubes displayed a jp of 96 mA cm-2. In terms of onset potentials, both materials presented values of -0.30 ± 0.04 V. Additionally, PdNi nanocubes displayed superior durability.

Figure 1
Effect of Ptm (Bi, Mo) Sub < 10 Nm Nanoparticles Supported on N-Doped Carbon on the Crude Glycerol Electro-Oxidation Reaction
Authors: Vera-Campos Maritza , Velázquez-Hernández Isaac , Rodriguez Valadez Francisco Javier , Álvarez-Contreras Lorena , Guerra-Balcázar Minerva , González-Nava Catalina , Arjona Noé
Published: May 2020

In this work, Pt, PtMo and PtBi materials with 1:1 atomic ratios were synthesized by a typical aqueous reduction method and used as electrocatalysts for glycerol and crude glycerol electro-oxidation reactions. Additionally, these nanomaterials were supported on N-doped carbon obtained from the carbonization of hemispherical polyaniline nanoparticles obtained by chemical methods. Crude glycerol was obtained from the Biodiesel production through the transesterification reaction of vegetal oils from a rotisserie and from a seafood restaurant located in Cortazar, Mexico. Physicochemical characterization indicated that the N-doped carbon support displayed a BET surface area of 483.8 m2 g-1, which is twice the reported value for benchmarked Vulcan carbon XC-72R (~230 m2 g-1). High-resolution transmission electron micrographs (HR-TEM), revealed that all materials presented particle sizes below 10 nm, while the particles displayed good dispersion on the support. Electrochemical evaluation indicated that the use of N-doped carbon as support on Pt nanoparticles achieved an onset potential (Eonset) of -0.48 V vs. NHE, which is only 210 mV more positive to the standard potential (-0.69 V vs. SHE). The use of Mo as co-metal did not influence the Eonset, but it increased 2.6 times the current density in comparison with Pt/N-doped C. On the other hand, the use of Bi as a p-block co-metal improved the Eonset achieving -0.54 V vs. NHE, while the resulting current density was 4.13 times higher to that obtained for Pt/N-doped C.
Surface-Dependent Phenomena in Cobalt-Based Electrocatalysts for Improved Nitrogen Oxyanion Reduction
Authors: Kulesa Krista M. , Fahey Mackenzie M. , Zaleski Jeff M. , Smith Jeremy M.
Published: May 2020

More than half of the world is fed and fueled through the Haber-Bosch process, and ammonia consumption and global population continue to grow in tandem. However, resulting nitrogen oxyanion (NOx) waste threatens aquatic ecosystems by feeding harmful algal blooms. Molecular transition metal electrocatalysts are poised to selectively reduce these NOx waste products: macrocyclic complexes are particularly robust to electrocatalytic N–O bond activations. Here, two cobalt-based macrocycles with redox-active ligand frameworks prove capable of reducing nitrate and nitrite, with an intriguing dependence on surface interactions. With an applied potential under monochromatic irradiation, a cobalt(III)-based diiminomethyl macrocycle, [Co(DIM)Br2]+, can more efficiently reduce NO2
– to ammonia by bypassing an auto-destructive ligand-based radical. Similarly, an intermediate with ligand-radical character is active toward NO3
– reduction in cobalt(II) tetraphenylporphyrin (CoTPP) in bulk systems, but can be stabilized in aqueous conditions for more affordable onset potentials once immobilized. Inspired by surface influence, homogeneous and heterogeneous systems are blended into molecular catalyst-support assemblies: physisorbing CoTPP on nanosupports imparts catalyst durability and nitrate electroreduction in coordinating buffers. These hybrid assemblies remarkably improve onset potentials in previously inaccessible conditions, ultimately overcoming many compromises between overpotential and turnover in purely homogeneous designs.

Figure 1
2D Semi-Metallic TiS2 Electrocatalyst for CO2 Conversion
Authors: Aljabour Abdalaziz
Published: May 2020

Two-dimensional transition metal dichalcogenides (TMDCs) are the most efficient and selective electrocatalysts for the heterogenous CO2 reduction to CO, along with MoS2, WS2, and their diselenides.[1, 2] Here we show CO electrosynthesis using atomic layer deposited TiS2 with a maximum Faraday yield of 64 % at an overpotential of less than 0.4V at 5 mA cm-2. We provide mechanistic insights on the electrosynthesis of C=O by the insitu ATR-FTIR spectroelectrochemistry. Operando studies reveal that the reason of high CO selectivity is due to the CO2 binding on active disulfide planes. Paired with mild synthesis protocol, reasonable stability and low-cost production, semi-metallic TiS2 promises satisfying applicability in CO2 electroreduction and utilization technology.

[1] P. Abbasi, M. Asadi, C. Liu, S. Sharifi-Asl, B. Sayahpour, A. Behranginia, P. Zapol, R. Shahbazian-Yassar, L.A. Curtiss, A. Salehi-Khojin, Tailoring the edge structure of molybdenum disulfide toward electrocatalytic reduction of carbon dioxide, ACS nano, 11 (2016) 453-460.

[2] M. Asadi, K. Kim, C. Liu, A.V. Addepalli, P. Abbasi, P. Yasaei, P. Phillips, A. Behranginia, J.M. Cerrato, R. Haasch, P. Zapol, B. Kumar, R.F. Klie, J. Abiade, L.A. Curtiss, A. Salehi-Khojin, Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid, Science, 353 (2016) 467-470.
Mimicking Noble Metals Using Hydrogen-Bonded Conducting Polymers for Electrocatalysis
Authors: Coskun Halime , Aljabour Abdalaziz , Yoshida Tsukasa , Stadler Philipp
Published: May 2020

The most active and efficient catalysts for the electrochemical hydrogen evolution reaction rely on noble metals, a fact that increases the cost of producing hydrogen and thereby limits the widespread adoption of this fuel. Here we present metal-free polydopamine and polyguanine as selective organic hydrogen electrocatalysts1–3. The conducting functional polymers incorporate selective hydrogen-affine hydrogen bonds that possess a similar hydrogen binding energies and work function as e.g. platinum. We report the synthesis of hydrogen-selective electrocatalytic polyguanine and polydopamine and demonstrate the enhancement of the rate-determining step in the proton reduction. We further present mechanistic spectral IR-operando studies on the catalytic hydrogen bonded motifs as well as the continuous electrolysis to molecular hydrogen using polyguanine and polydopamine electrodes for several 100 hours without notable degradation.

(1) Coskun, H.; Aljabour, A.; Schöfberger, W.; Hinterreiter, A.; Stifter, D.; Sariciftci, N. S.; Stadler, P. Cofunction of Protons as Dopant and Reactant Activate the Electrocatalytic Hydrogen Evolution in Emeraldine‐Polyguanine. Adv. Mater. Interfaces 2019, 1901364 DOI: 10.1002/admi.201901364.

(2) Coskun, H.; Aljabour, A.; Uiberlacker, L.; Strobel, M.; Hild, S.; Cobet, C.; Farka, D.; Stadler, P.; Sariciftci, N. S. Chemical Vapor Deposition - Based Synthesis of Conductive Polydopamine Thin-Films. Thin Solid Films 2018, 645 (August 2017), 320–325 DOI: 10.1016/j.tsf.2017.10.063.

(3) Coskun, H.; Aljabour, A.; Luna, P. De; Sun, H.; Nishiumi, N.; Yoshida, T.; Koller, G.; Ramsey, M. G.; Greunz, T.; Stifter, D.; Hassel, A. W.; Sariciftci, N. S.; Sargent, E. H.; Stadler, P. Hydrogen-Bonded Polymers Mimic Noble Metal Electrocatalysts. Adv. Mater., submitted.
Thermally Treated Anodically Formed Titanium Oxide Nanotubes Producing Desirable Electrocatalytic Properties
Authors: Malik Hammad , Carlson Krista , Mohanty Swomitra K. , D'Agostini Rachel
Published: May 2020

Highly ordered anodically formed titanium oxide nanotubes possess high surface area, biocompatibility and chemical inertness. These properties make them potentially useful for many applications, but these nanotubes are insulative and possess a high band gap limiting their usefulness. Hence, these NTs cannot be directly used for electrocatalysis. Synthesis of titanium oxide nanotubes with good electrocatalytic properties has been a challenge. This study reports on the synthesis of anodically formed NTs with desirable electrocatalytic properties through annealing treatment in 2% hydrogen with a nitrogen balance (H2N2). The changes in the flat band potential, donor density, double layer capacitance and diameter of double layer was investigated using the Mott Schottky plots. The results from the electrochemical testing, scanning electron microscopy (SEM), UV-visible spectroscopy (UV-Vis) for oxygen (O2) annealed NTs and H2N2 annealed NTs were compared to establish a relationship between the effect of gaseous environment on the structure of the NTs and the change in electrocatalytic properties encountered.
Surface Plasmon Resonance of Au Thin Films Modified By Catalyst Monolayer
Authors: Artur Camille , Salavati-Fard Taha , Yarali Miad , Mayerich David , Grabow Lars , Shan Xiaonan , Brankovic Stanko
Published: May 2020

In this talk, we present the results and modeling o the catalyst monolayer modification effects on plasmon resonance of Au thin films. The experiments are conducted using an attenuated total reflection arrangement in which p-polarized light is incident through a prism onto a thin (-400 A) Au film deposited on the mica substrate. (Kretschmann configuration [[1]]). The angle of incidence on the base of the prism is greater than the critical angle for the prism: electrolyte interface and SPs are excited by the evanescent wave generated under these conditions of total internal reflection. The excitation is manifested by a decrease in the intensity of reflected light. The Pd monolayer on Au were electrodeposited using procedure reported by Kolbe et al [[2],[3]], while the Pt submonolayer/monolayers were deposited on Au using Surface Limited Redox Replacement (SLRR) of Pb UPD monolayer [[4]]. The plasmon resonance frequency of Au(hkl), PdML/Au(hkl) and PtML/Au(hkl) and PtSML/Au(hkl) were investigated as a function of the applied potential in the range between -0.24 V to 0.4 V vs. SCE. The comparative analysis, between Au and catalyst monolayer modified Au(hkl) samples indicate that SP resonant frequency change is induced by both; surface charge and dipole moment of the surface as well as he adsorption of H on the catalyst monolayer surface in the UPD region. The latter effect is quantified using subtractive analysis between the Au and catalyst modified Au surface and solutions with different pH. In conclusion, we present a simple model describing the catalyst monolayer effect on plasmon resonance of Au films.

[1] E. Kretschmann and H. Raether, Z. Natutforsch. 23a (1968) 2135.

[2] L.A. Kibler, M. Kleinert, R. Randler, D.M. Kolb, Surface Science, 443 (1999) 19.

[3] J. Tang, M. Petri, L.A. Kibler, D.M. Kolb, Electrochimica Acta, 51, (2005) 125

[4] K. Sasaki et al, Electrochim. Acta, 55, (2010) 2645.
Atomically Thin Film Platinum Supported Sub-Stoichiometric Titania: A Tunable Electrocatalyst for Fuel Cell Reactions
Authors: Bell Crystal , Drexler Matthew N , Yang Stella , Sasaki Kotaro , Alamgir Faisal M.
Published: May 2020

Designing efficient catalyst for fuel cell devices has gained an increasing amount of attention over the last decade for chemical to electrical energy conversion. The widespread commercialization of fuel cells, such as proton exchange membrane fuel cells, are hindered by the sluggish kinetics of the cathodic oxygen reduction reaction, the costly platinum catalyst employed within the cell, along with long-term catalyst degradation. One approach aimed at simultaneously addressing these drawbacks is to synthesize atomically thin film platinum on a robust support. While many catalysts are being investigated for fuel cell reactions, Pt based catalysts are in high demand due to stability, high activity, and low overpotential. We demonstrate an unprecedented electrochemical deposition of Pt on graphene/sub-stoichiometric titania supports (Ti2O3 and Ti3O5).

Ti2O3 and Ti3O5 films were deposited on silicon wafers via pulsed laser deposition. Four-point probe measurements, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), ultraviolet photoelectron spectroscopy (UPS), and Scanning Electron Microscopy (SEM) were used to examine the chemical, electrical, and morphological properties of the sub-stoichiometric supports. Chemical vapor deposited graphene on copper foil was transferred through a series of etchants to produce the Gr/TixO2x-1
(x=1 or 2) support. Incorporating a graphene interfacial layer between Pt and TixO2x-1 served as a platform for large-area, fully wetted growth of two-dimensional Pt films. Pt thin films were electrochemically co-deposited on Gr/TixO2x-1 supports in an aqueous solution consisting of Pt2+ and Cu2+.The chemical and morphological properties of the electrochemically deposited Pt films were investigated using XPS and SEM, respectively. Pt films were found to exist in a metallic state. The functionality of the synthesized catalyst was tested using major fuel cell reactions including, oxygen reduction, methanol oxidation, and ammonia oxidation reactions. Overall, varying the stoichiometry of the TixO2x-1 supports leads to reaction overpotential tunability as predicted by fluctuations in the work-function of the support. This study provides insights on the preparation of a novel Pt/Gr/TixO2x-1 catalyst aimed at developing clean energy devices.