bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacial Effect Study of Alkaline Membrane Media Using Microelectrodes
Authors: Malley Jenna , Doan Huong , Gunasekara Iromie , Mukerjee Sanjeev
Published: February 2020

Interfacial issues at anion exchange membranes greatly influence the electrocatalysis at high pH environment especially in conjunction with an anion exchange membrane. In this context it is well known that carbonate ions in the context of a prototypical anion exchange membrane such as A 201 (Tokuyama, Japan) are strongly adsorbing anions and thus can suppress HOR kinetics. Not only can carbonate ions block catalyst active sites, but they can also lower the amount of hydroxyl ions for adsorption at low pH. Moreover, corresponding ionomers such as AS-4 (Tokuyama, Japan) has a negative effect on HOR activity in the context of Pt, as shown in Figure 1c. At NUCRET, we successfully concluded the effect of carbonates in conjunction of anion exchange membrane as well as the role of corresponding ionomers such as AS-4. In this study we further extend this investigation by including microelectrodes in two different media - carbonate and hydroxide - for HER (Pt microelectrode) and OER (Ir microelectrode). Hence this presentation will include the following work:

Using A 201 in hydroxide form and carbonate form in the Solid State Cell setup (Figure 1a), under the following scenarios:

1) Water fed vs. KOH vs.K2CO3 continuous feed (for electrolytes, equal conductivity and equal pH conditions);

2) HER/HOR and OER/ORR while feeding electrolyte from the top, bottom, or both.

This study is aimed at understanding the improvements observed when feeding a low concentration of carbonate at the anode interface (OER electrode) during water electropysis (Figure 1b). We hypothesize that the improvement could be because of the conductivity boost from 1% carbonate, because of different reaction mechanisms between HER (cathode side) and OER, or both. This micro-electrode study therefore is designed to not only mimic carbonate vs. hydroxide at the membrane interface via directional feed of carbonate ions (i.e., top where the microelectrode is at an interface with the membrane) or bottom to mimic mass transport and kinetics at the membrane interface. Transferring this study to the practical water splitting cell, will provide a thorough insight of the reactions between the catalyst layer and the membrane while feeding water vs. different electrolytes. It is particularly important to note that A-201 standard (Tokuyama, Japan) represents the state-of-the-art in alkaline membranes. Currently, our partner - Proton On-Site provides the full cell scale-up water splitting stack with the use of our best non-PGM catalysts for HER (60% Ni-Cr/C) and OER (40% Ni-Fe/Raney-PANI), as well as feeding 1% carbonate on the anode side.

Figure 1
One Step Synthesis of Cos-Doped β-Co(OH)2@Amorphous MoS2+X Hybrid Catalyst Grown on Nickel Foam for High Performance Electrochemical Overall Water Splitting
Authors: Yoon Taeseung
Published: February 2020

Developing efficient and economical electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with readily available metals is one of the main challenges for large scale hydrogen/oxygen production. Here, we report one step synthesis of cobalt and molybdenum hybrid materials for high performance overall water splitting. The binder-free CoS-doped β-Co(OH)2@amorphous MoS2+x is coated on nickel foam (NF) to form 3D networked nanoplates which have large surface area and high durability for electrochemical reactions. The catalytic activity of electrocatalyst for hydrogen evolution is mainly attributed to the unsaturated sulfur site of amorphous MoS2+x. Meanwhile, the CoS-doped β-Co(OH)2 plays the major role in oxygen evolution. CoS-doped β-Co(OH)2 and aMoS2+x are strongly bound to each other due to CoSx bridging. This CoS-Co(OH)2@aMoS2+x/NF hybrid exhibits excellent catalytic activity and stability for overall water splitting. For over 100,000 seconds the cell voltage required to achieve the current density of 10 mA cm-2 is only 1.58 V, which is remarkably low among the commercially available electrocatalysts. Our findings would open up an easy and inexpensive method of large scale fabrication of bifunctional electrocatalysts for overall water splitting.

Figure 1
Compositional Optimization of Alloy FexNiy(OH)2 Nanoparticles for Alkaline Electrochemical Oxygen Evolution
Authors: Greenlee Lauren F , Acharya Prashant , Nelson Zachary
Published: February 2020

It has recently been demonstrated by Bell and co-authors [1] that intentional iron doping into a nickel hydroxide film causes significant enhancement in electrochemical performance for the oxygen evolution half reaction (OER) of alkaline electrolysis. A subsequent study by Boettcher and co-authors [2] demonstrated that unintentional iron doping of a nickel hydroxide catalyst occurs from ppm- to ppb-level iron contaminants in alkaline electrolytes; the iron incorporates into the nickel hydroxide structure, and causes at least an order of magnitude increase in current density. Freibel et al. subsequently demonstrated that iron may in fact be the active site of OER, with nickel hydroxide acting as a host [3]. The majority of the work thus far investigating how iron content in an FexNiy(OH)2 catalyst affects OER has been performed on thin film catalysts; Burke et al. specifically describe the need for catalyst architectures that reduce mass transport limitations and allow improved access to more active sites per unit mass of catalyst [4]. As a result, there is an interest in developing nanoscale catalysts that are composed of iron and nickel and result in greatly improved performance metrics for OER over their thin film counterparts. Here, we will present results for the optimization of a FexNiy(OH)2 nanoparticle catalyst. In this work, the nanoparticles are synthesized with an alloy morphology and the atomic ratio of iron to nickel is varied from 1:5 to 5:1. Once synthesized, the nanoparticles are evaluated in 1 M KOH that has been purified to remove any iron impurities. Electrochemical performance of this series of nanoparticle catalysts will be discussed as well as our efforts to characterize the nanoparticles with electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction.

[1] M.W. Louie, A.T. Bell, An investigation of thin-film Ni-Fe oxide catalysts for the electrochemical evolution of oxygen, J. Am. Chem. Soc., 135 (2013) 12329-12337.

[2] L. Trotochaud, S.L. Young, J.K. Ranney, S.W. Boettcher, Nickel-iron oxyhydroxide oxygen-evolution electrocatalysts: The role of intentional and incidental iron incorporation, J. Am. Chem. Soc., 136 (2014) 6744-6753.

[3] D. Friebel, M.W. Louie, M. Bajdich, K.E. Sanwald, Y. Cai, A.M. Wise, M.-J. Cheng, D. Sokaras, T.-C. Weng, R. Alonso, R.C. Davis, J.R. Bargar, J.K. Norskov, A. Nilsson, A.T. Bell, Identification of highly active Fe sites in (Ni,Fe)OOH for electrocatalytic water splitting, J. Am. Chem. Soc., 137 (2015) 1305–1313.

[4] M.S. Burke, L.J. Enman, A.S. Batchellor, S.H. Zou, S.W. Boettcher, Oxygen evolution reaction electrocatalysis on transition metal oxides and (oxy)hydroxides: Activity trends and design principles, Chemistry of Materials, 27 (2015) 7549-7558.
High Surface Area NanoCOT Catalysts on Ni Foam Framework for Efficient Water Electrolysis
Authors: Dyer Elizabeth , Hitt Jeremy , Shan Zhichao , Pan Shanlin
Published: February 2020

Carbon doped nanostructured TiO2 electrodes (NanoCOT) are prepared by anodizing titanium in a fluoride-based electrolyte followed by thermal annealing in an atmosphere of methane and hydrogen in the presence of Fe precursors. NanoCOT are highly conductive and contain more than 1 × 10^9 /cm2 of nanowires or nanotubes to enhance their double layer charge capacitance and electrochemical stability. This electrode material also exhibits enhanced oxygen evolution reaction (OER) catalytic activity in alkaline solution, providing a current density of 1.33 mA/cm2 at an overpotential of 0.42 V. This OER current density of a NanoCOT electrode is about 4 times higher than an oxidized Ir electrode and 15 times higher than a Pt electrode because of its nanostructured high surface area and favorable OER kinetics. The enhanced catalytic activity of NanoCOT is attributed to the presence of a continuous energy band of the titanium oxide electrode with predominantly reduced defect states of Ti (e.g., Ti^1+, Ti^2+, and Ti^3+) formed by chemical reduction with hydrogen and carbon. The OER performance of NanoCOT can also be further enhanced by decreasing its overpotential by 150 mV at a current density of 1.0 mA/cm2after coating its surface electrophoretically with 2.0 nm IrOx nanoparticles. Further improve can be obtained by using porous substrate such as Ni and Ti foam.
(Invited) Developing Efficient Electrocatalysts for the Hydrogen and Oxygen Evolution Reactions
Authors: Yeo Boon Siang
Published: February 2020

Water electrolysis is one of the crucial means for converting electricity generated from solar and wind based power sources into clean H2 fuels. The efficiency of this process depends largely on the catalytic property of the cathode and anode.We present here our work to develop and understand electrocatalysts used for the oxygen (OER) and hydrogen (HER) evolution reactions. Using operando Raman spectroscopy, we shall first show how the structure of amorphous MoS
x
(an excellent HER catalyst) evolves during H2 evolution. Furthermore, we have identified the S atoms therein as the catalytically active sites responsible for proton reduction. Density functional theory calculations were performed on a variety of MoS
x
structures and corroborated the assignments of the observed vibrational frequencies. We shall also present our Raman and X-ray absorption spectroscopy study of Cu oxides during O2 evolution. This investigation has allowed us to propose CuIIIoxides as highly active catalytic species for the electrochemical water oxidation. Mixed metal composites based on Mo and W have also been shown to exhibit excellent HER activities. We elucidated the catalytic roles of the different elements therein such as nitrogen, carbon, molybdenum, etc , and proposed plausible mechanisms of their workings. We shall show that some of these catalysts are robust against deactivation even in contaminated electrolytes. Finally, we present an overview of our recent work to couple photovoltaics to an electrocatalytic cell for the efficient reduction of carbon dioxide.

1. Y.L. Deng, L.R.L. Ting, P.H.L. Neo, Y.J. Zhang, A.A. Peterson, and B.S. Yeo. ACS Catal. 6, 7790.
2016.

2. Y.L. Deng, A.D. Handoko, Y.H. Du, S.B. Xi and B.S. Yeo. ACS Catal. 6, 2473. 2016

3. L.R.L. Ting, Y.L. Deng, L. Ma, Y.J. Zhang, A.A. Peterson, and B.S. Yeo. ACS Catal. 6, 861. 2016

4. U. Joshi, J. Lee, C. Giordano, S. Malkhandi and B.S. Yeo.  Phys. Chem. Chem. Phys. 18, 21548. 2016.
Implementing Structural Defects As a New Direction to Improve the Durability of Pt-Based/C Nanoparticles
Authors: Dubau Laetitia , Nelayah Jaysen , Chattot Raphaël , Asset Tristan , Bordet Pierre , Drnec Jakub , Maillard Frederic
Published: February 2020

Due to strain and ligand effects, the simultaneous presence of concave and convex surfaces and their highly-defective nanostructure (atomic vacancies, grain boundaries), hollow Pt-rich/C electrocatalysts have proven to enhance remarkably the oxygen reduction reaction (ORR) kinetics. However, a technologically-relevant proton-exchange membrane fuel cell (PEMFC) cathode catalyst should be able to maintain its initial catalytic activity on the long-term. This is hardly feasible on nanocatalysts based on platinum alloyed with transition metals (PtM alloys, M being a transition metal) or M-rich core@Pt-rich shell nanoparticles due to the dissolution of the transition metal in the harsh operating conditions of a PEMFC cathode but the question remains open for nanocatalysts in which catalytic activity is not solely due to alloying effects. Herein, the ORR activity of solid or hollow PtNi/C nanoparticles with identical chemical composition but different fine nanostructure was evaluated before and after accelerated stress tests (ASTs) under simulated PEMFC operating conditions (5,000 potential cycles between 0.6 and 1.0 V vs. RHE at T = 80°C). Independently on the nanostructure, the combined physical, chemical and electrochemical results show that the losses in ORR activity are related to weakening of strain and ligand effects associated with the dissolution of Ni atoms. However, the catalytic advantage of hollow over solid PtNi/C nanoparticles was maintained during the ASTs. Hence, implementing structural disorder in PEMFC cathode electrocatalysts represents a new direction to look at to improve sustainably the ORR kinetics.

Figure 1
(Invited) Shape Fixing By Salt Nanoreactor to Produce Nanocarbon Materials for the Catalysis of Oxygen Reduction Reaction
Authors: Wei Zidong , Ding Wei , Li Li , Chen Siguo , Qi Xueqiang
Published: February 2020

Developing catalytic materials for oxygen reduction reactions (ORR) with high performance and low cost has been one of the major challenges for large-scale applications of fuel cells. We demonstrated a high-yield " shape fixing via salt recrystallization" method to efficiently synthesize N-doped carbon nanomaterials with a high density of active sites, as an ORR catalyst. The process of shape-fixing involves pouring a supersaturated sodium chloride (NaCl) solution onto a 3D polyaniline (PANI) carbon-based polymer in a beaker, which results in the water evaporating and NaCl recrystallizing around the PANI until the PANI is fully covered by crystals. The NaCl crystal functions as a fully sealed nanoreactor which facilitates the N incorporation and graphitization. The gas from gasification in such a closed nanoreactor produces a large quantity of pores in resultant samples, and the carbonized PANI retains its original 3D shape due to previously being shape-fixed by the NaCl crystal. This makes it possible for the active sites (activated by planar pyridinic and pyrrolic N atoms with sp2 hybrid orbitals, which only appear at the outside fringe of a graphene sheet) to appear in large quantities on the edges of numerous pores. Such favorable catalyst structure leads to the availability of efficient mass transport pathways and a high utilization of the active sites in fuel cell. It results in an excellent ORR activity with a half-wave potential only 58 mV behind that of Pt/C in an acidic medium. The proton-exchange membrane fuel cells with the CPANI-Fe-NaCl-catalyzed cathode outputs a peak power of 600 mW cm-2, which is among the best for non-precious metal catalysts reported so far for the ORR. Additionally, no other method is comparable to this invention, in terms of its high yield per batch of N-doped carbon catalysts. The “shape fixing via salt recrystallization” method represents a powerful approach for the preparation of high-performance carbon nanostructures by confined pyrolysis of nanopolymers and, more importantly, provides insight into the design of advanced PEMFC cathode catalysts.

References

[1] W. Ding, Z. D. Wei, S. G. Chen, X. Q. Qi, T. Yang, J. S. Hu, D. Wang, L.-J. Wan, S. F. Alvi, L. Li.  Angew. Chem. Int. Ed.
2013, 52, 11755.

[2] W. Ding, L. Li, K. Xiong, Y. Wang, W. Li, Y. Nie, S. G. Chen, X. Q. Qi, Z. D. Wei. J. Am. Chem. Soc.,
2015, DOI: 10.1021/jacs.5b002.
Study on Highly Conductive and Anti-Corrosion Titanium Oxide-Supported Pt Catalysts for Oxygen Reduction Reaction
Authors: Duma Alemayehu Dubale
Published: February 2020

Study on Highly Conductive and Anti-Corrosion Titanium oxide-Supported Pt Catalysts for Oxygen Reduction Reaction

Alemayehu Dubale Duma,a Yu-Chen, Wu a, Wei Nien Su,*b Chun-Jern Pan, a Meng-Che Tsai,a Hung-Ming Chen, Jyh-Fu Lee, Hwo-Shuenn Sheu, Van Thi Thanh Ho and Bing-Joe Hwang*ac

aNanoelectrochemistry Laboratory, Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, 106, Taiwan.

b
2NanoElectrochemistry Laboratory, Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan

3National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan

e-mail:alexdubale@gmail.com
Abstract

The sluggish rate of the oxygen reduction reaction (ORR) and the durability of Pt-based catalysts along with the carbon corrosion on the cathode side, have been recognized as critical issues associated with the durability of catalyst restricting their application towards wide applications for proton exchange membrane fuel cells (PEMFCs). We present herein, a synthesis of a series of highly conductive modified Titanium oxide-supported Pt catalysts and their respective electrochemical performance investigated for use in the oxygen reduction reaction. TiO2 nanoparticles were synthesized using a solvothermal method before their surface was coated by using Hexamethyldisilazane (HMDS) so as to inhibit the particle growth during the succeeding high temperature treatment under H2 environment, where they eventually transformed to Ti4O7, when the temperature rises to 1000 ℃. Structural and electronic properties of the support materials and the subsequent catalysts are characterized by various approaches, including X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray absorption spectroscopy (XAS). It was found that the electrical conductivity of TiO2 increases with increasing reduction temperature, but at the expense of decreased surface area. The electrochemical performance reveals that the Pt catalyst based on HMDS modified TiO2 support, which was subjected to H2 reduction at 850℃, namely (20Pt 850 FHST), exhibited better activity when compared to others in the same series with a maximum current density of 0.049 mA/cm2 at 0.9 V (vs. NHE) and an onset potential of 0.86 V (vs. NHE). The prolonged cycling test also exhibited that HMDS modified 20Pt 850 FHST catalyst possesses superior durability to commercial catalyst (JM 20 Pt/C). X-ray absorption spectroscopy (XAS) further confirms that higher electron population of Pt 5d-orbital improves the electrochemical activity in which this catalyst shows the improved performance for ORR compared to others within the series i.e. different H2 reduction temperatures.

Keyword
s: Oxygen reduction reaction, Fuel cell, Strong Metal Support Interaction, Titanium oxide
Tracking Ion Migrations at the Nanoscale in Rechargeable Batteries Using Advanced Transmission Electron Microscopy
Authors: Su Dong
Published: February 2020

Advanced (scanning) transmission electron microscopy ((S)TEM) has been applied to study the redox reactions of the electrode materials for secondary ion batteries. With/Combining different TEM techniques (including in situ TEM and diffraction, HAADF-STEM, and STEM-electron energy-loss spectroscopy (EELS)), researchers are able to probe local structural and chemical information of electrode materials, at a resolution of nanoscale. Knowledge about the reaction dynamics and kinetics can be retrieved at different states of charging (discharging). This talk will cover the recent progress on TEM characterization of the conversion compounds for lithium/sodium ion batteries. While the ex situ TEM study reveal the structural change in the real cell, in situ TEM study can help us to understand the process of lithiation/sodiation. In the cases of rocksalt-structure oxide(NiO)and spinel oxides(Fe3O4 and Co3O4) compounds for electrode materials, we investigated the dynamical process of the redox reaction in real time. The role of reaction pathways is highlighted which is supposed to affect the batteries’ kinetic properties. Our results may give insights in developing new electrode materials for high performance batteries.
In Situ Investigation of the Interface of Photoanodes and Electrocatalysts in Photoelectrochemical Water Oxidation Using Dual Working Electrode Photoelectrochemistry
Authors: Qiu Jingjing , Nellist Michael R. , Laskowski Forrest A. L. , Boettcher Shannon W.
Published: February 2020

Light-absorbing semiconductor electrodes decorated with electrocatalysts are key components of photoelectrochemical energy conversion and storage systems. Efforts to optimize these systems have been slowed by an inadequate understanding of the semiconductor (SC) and electrocatalyst (EC) interface. Experiments to directly measure the interface behavior are challenging because conventional photoelectrochemical techniques do not measure the electrocatalyst potential during operation. We developed dual working electrode (DWE) photoelectrochemistry to address this limitation. A second electrode is attached to the catalyst layer to control and probe current/voltage independent from that of the semiconductor.

The DWE investigations on a model system TiO2 reveal that electrolyte-permeable ECs form an “adaptive” junction with the semiconductor. This talk will focus on studies of the interface of the visible-light-absorbing semiconductor α-Fe2O3 and the electrocatalyst a-Ni80Fe20O
x
with DWE photoelectrochemistry. We discover that the potential at the SC|EC interface changes in situ with the oxidation level of the EC. Additionally, the activation of EC film is vital to the charge transport between SC and EC. A fully-activated amorphous Ni(Fe)OOH film can harvest the vast majority of photo-generated holes from α-Fe2O3 electrodes.
(Invited) Modification of Electrocatalytic and Photoelectrochemical Interfaces Toward More Efficient Reduction of Carbon Dioxide
Authors: Kulesza Pawel J , Wadas Anna , Szaniawska Ewelina , Zoladek Sylwia , Rutkowska Iwona Agnieszka
Published: February 2020

There has been growing interest in the photoelectrochemical conversion of carbon dioxide to useful carbon-based fuels or chemicals. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the photo(electro)chemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.

Recently, we have concentrated on the development of hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. For example, the combination of titanium (IV) oxide and copper (I) oxide has been considered before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. Among important issue is intentional stabilization, activation, and functionalization of the mixed-metal-oxide-based photoelectrochemcal interface toward better long-term performance and selectivity production of small organic molecules (C1-C4) and other chemicals. In this respect, ultra-thin films of conducting polymers (simple or polyoxometallate-derivatized) and supramolecular complexes (with nitrogen containing ligands and certain transition metal sites), sub-monolayers of metals (Cu, Au), networks of noble metal (Au, Ag) nanoparticles or layers of robust bacterial biofilms have been considered.

We are also going to demonstrate that the photoinduced electron from semiconductor conduction band is capable of activation of the active center of the metalo-enzyme molecule. Here the.nanostructured silicon material has been chosen as the substrate for the enzyme adsorption. In this case the p-type Si(111) was etched toward formation of the bunched steps on the surface. The photo-biocathode with Cu-containing enzyme has induced the reduction of not only oxygen but carbon dioxide as well, under illuminations with photon energies higher than silicon band gap.

In the presentation, special attention will be paid to mechanistic aspects of electroreduction of carbon dioxide, fabrication and characterization of highly selective and durable semiconductor photoelectrode materials and to importance of the reaction conditions.
Effect of CdSe Quantum Confinement on Charge Transfer Kinetics in Solar-Driven Hydrogen Production from Urea
Authors: Radich James , Zhao Rong
Published: February 2020

Urea has been proposed as a source to produce hydrogen. We describe here CdSe-sensitized TiO2 assembled with urea electrocatalyst, Ni(OH)2, on fluorine-doped tin oxide (FTO) coated glass (FTO/TiO2/CdSe/Ni(OH)2) used as photoanode for simultaneous urea oxidation and water reduction using visible light irradiation. The steady-state photoresponse of the semiconductor-catalyst electrode in the photoelectrochemical system is investigated, and the CdSe quantum confinement effect on charge transfer kinetics is investigated by employing transient absorption spectroscopy. The obtained carrier dynamics reveal the reaction mechanism and indicate the change of the CdSe band position and hence driving force for charge transfer.
The Influence of Inverse Opal Template and Substrate Type on Electrodeposited 3D Macroporous Oxides
Authors: O'Hanlon Sally , McNulty David , O'Dwyer Colm
Published: February 2020

The objective of this study is a detailed investigation into the preparation of V2O5 inverse opals using electrodeposition into preformed colloidal opal templates as a function of electrodeposition parameters (sphere size, voltage, time and substrate). Inverse opals have a range of applications(1-3) and many materials can now be formed into 3D macroporous IO structures.(4-6) Electrodeposition of a VOSO4 aqueous solution in to the inverse opal template is investigated on three different substrates; transparent conducting oxide glass, stainless steel, and thermally oxidized stainless steel. The electrodeposition follows a diffusion limited growth mode to form 3D porous crystalline V2O5 after removal of the colloid photonic crystal template of self-assembled polystyrene spheres. Inverse opals were grown using spheres ranging in diameter from 0.5 µm to 6 µm, and binary inverse opals are also electrodeposited using binary mixtures of sphere size. Analysis of the electrodeposition growth profiles show that IO growth in single and binary opal templates is diffusion limited and that pre-heating stainless steel forms an oxide coating that forces the initial current to increase to a steady state to overcome the resistive oxide, allowing IO to electrodeposit at relatively constant rate. Tortuosity is significantly increased when large sphere diameter templates are used, and especially pronounced when binary opal templates are used, because of interstitial void filling by small spheres in binary opal templates. Raman scattering and X-ray diffraction confirm phase pure, high crystalline quality V2O5 is generally formed in all cases (voltages and substrates). Electrodeposition ensures electrical interconnection within the 3D structured material by definition.

References

1. E. Armstrong and C. O'Dwyer, J. Mater. Chem. C, 3, 6109 (2015).

2. D. McNulty, H. Geaney, E. Armstrong and C. O'Dwyer, J. Mater. Chem. A, 4, 4448 (2016).

3. M. Osiak, H. Geaney, E. Armstrong and C. O'Dwyer, J. Mater. Chem. A, 2, 9433 (2014).

4. H. Liu, H.-M. Cho, Y. S. Meng and Q. Li, ACS Appl. Mater. Interfaces, 6, 9842 (2014).

5. S. J. Yeo, H. Kang, Y. H. Kim, S. Han and P. J. Yoo, ACS Appl. Mater. Interfaces, 4, 2107 (2012).

6. E. Armstrong, M. O'Sullivan, J. O'Connell, J. D. Holmes and C. O'Dwyer, J. Electrochem. Soc, 162, D605 (2015).

7. Y. Zhao, X. Li, J. Liu, C. Wang, Y. Zhao and G. Yue, ACS Appl. Mater. Interfaces (2016).
Solvation of Sodium Salts in Glymes
Authors: Galle Kankanamge Susith R , Kuroda Daniel G
Published: February 2020

Sodium ion batteries are promising candidates to replace high cost lithium ion batteries due to the high natural abundance of sodium. However, conventional graphite anodes cannot be used in sodium ion batteries due to difficulties in intercalating sodium ions into graphite. Previous studies have shown that ether based electrolytes, such as glymes, are promising candidates since they do not present the problem of intercalation of sodium ions into graphite. Interestingly, the solvation of sodium ions in glymes has not been fully characterized. Here, we studied the solvation of sodium ions in glymes of different lengths, from two to four units, via two dimensional infrared spectroscopy, 2D-IR, and FTIR spectroscopy. Our studies show that the solvent molecules and counter ion play a significant role in the solvation of the sodium ion. For example, the sodium ion is mainly associated to its thiocyanate counter ion through the sulfur atom irrespective of the glyme length. Moreover, the ratio between free ions and ion pairs changes with the type of glyme. In addition, 2D-IR spectroscopic studies reveal the presence of two distinct motions in the molecular environment of the thiocyanate ion with the picosecond time scales that increase their characteristic times with the length of the glyme. In contrast, studies on sodium bis(trifluoromethane)sulfonimide (TFSI) in different glymes show a contrasting picture in which most of the counter ions do not form ion pairs with the sulfonate groups of the anion. Moreover, the TFSI ions do not seem to observe any changes in their dynamics in glymes of different lengths. Our results indicate that the molecular solvation of the sodium ion is strongly influenced by the effectiveness of the glyme to solvate the cation. However, the delocalization of the charge in the counter ion seems to be key for explaining the tendency of ion pair formation in glyme-based sodium ion electrolytes.
in-Situ Electrochemical-AFM and CV Measurement Study on the Nucleation and Growth in Reduced Graphene Oxide Electrode Contacts
Authors: Pyo Sung Gyu
Published: February 2020

Electrochemical atomic force microscopy (EC-AFM) is a composite electrochemical analysis method. A lot of researches have been done on this, and it has been applied in many fields. EC-AFM was composed of EC-Cell, electrochemical analysis system, AFM and so on. For electrochemical analysis system and AFM to be analyzed at the same time, EC-Cell with a suitable structure is required. In this study, we made an electrochemical system in AFM with CV measurement system for in-situ observation of the elctrochemical reaction. Based on the developed EC-Cell, EC-AFM experiment system which was developed by constructing EC-AFM analysis system and numerical analysis method were proposed and tested and studied. First, we confirmed the EC-AFM analysis procedure and analysis method developed by observing copper electrochemical corrosion process. Second, electrochemical reduction characteristics of graphene oxide were studied using electrochemical analysis. An electrochemical atomic force microscope (EC-AFM) was used to study the reaction of wet electrode in various electrolyte, when the reaction corresponding to what occurs at the electrode of an electrode deposition. We observed wet plated solar electrode process during cyclic-voltammetry (CV) measurement with atomic force microscopy, and then were obtained useful continuous in situ images of the surface morphology. These AFM images dynamically showed the surface morphology change during the electro deposition. It was confirmed that initial nucleation of electrode crystals occurs after supersaturation, and that the slow dissolving on CV. AFM images of the electrode crystal morphology were compared with those in a different potential sweeping rate and electrolyte concentration at CV. We also compared the difference in AFM images and SEM images that were observed on the same electrode sample. Finally, we investigated the copper electrochemical deposition process in reduced graphene oxide using EC-AFM and observed the copper film formation process on reduced graphene oxide surface. As a result, the EC-AFM analysis system was constructed and tested, and the electrochemical characteristics on the reduce graphene oxide surface were observed.
Nafion Film Investigations Using Ferricyanide As a Probe Molecule
Authors: Reynolds Marissa Kayle , Paul David W
Published: February 2020

Nafion membranes are a common choice in proton exchange membranes used in hydrogen-oxygen fuel cells. Their purpose is to separate the fuel and the oxidant within the cell, and allow protons from hydrogen oxidation to migrate through the Nafion membrane to the cathode. The electrons from the oxidation are thermodynamically pushed to the cathode through an external circuit where the current is driven through a load. One major issue with proton exchange membranes is their durability. Degradation can occur mechanically and chemically. In this work, a probe molecule, ferricyanide with hydrodynamic voltammetry was used to determine tears or imperfections in Nafion membranes cast over gold electrodes. Ferricyanide is negatively charged and therefore should not enter a Nafion membrane, any recorded red/ox signal indicates that the molecule has gained access to the bare electrode through an imperfection in the membrane. Hydrodynamic voltammetry was used to control the thickness of the solution diffusion layer thickness so that diffusion through the solution could be discriminated from diffusion processes in the membrane. During the work we also discovered, as others had, that negatively charged species1 and ferricyanide specifically2
can permeate into Nafion, albeit at a very slowly. This permeation rate is too slow to be recorded on the short time-scale of a hydrodynamic voltammetry experiment. However, if ferricyanide was included in the solution used to hydrate the membrane, a ferricyanide red/ox signal was seen indicating that approximately 0.4 mM had become trapped in the membrane (Figure 1). Moreover, only hydrated membranes containing ferricyanide, provide enough conductivity through the membrane to detect ferricyanide in solution (Figure 2). The signals obtained through these membranes were evaluated with a combination of the Koutecky-Levich equation3 and permeability equations from the Gough group4.

1. Unnikrishnan, E. K.; Kumar, S. D.; Maiti, B., Journal of Membrane Science
1997,
137, 133-137.

2. DeWulf, D.; Bard, A. J., J. Macromol. Sci., Chem.
1989,
A26 (8), 1205-9.

3. Bard, A. J.; Faulkner, L. R., Electrochemical Methods: Fundamentals and Applications. 1980; p 718 pp.

4. Gough, D. A.; Leypoldt, J. K., Analytical Chemistry
1979,
51 (3), 439-444.

Figure 1
Effects of Additives on the Electrodeposition of Nano-Grained Ni-Mo Alloys
Authors: Shi Y.N. , Hu J. , Zheng X.G. , Lu K.
Published: February 2020

Nano-grained (ng) materials have attracted much interest in the past few decades, as these materials are expected to have superior properties to their coarse-grained counterparts. Nevertheless, owing to the large fraction of grain boundary, the grain boundary energy becomes so high with the grain size down to a few nanometers that it is challenging to synthesize ng metals with extremely fine grain size. One possible way to do this is to prepare ng alloys instead of pure ng metals by choosing appropriate alloy systems with a tendency of segregation, as the segregation of solute atoms at grain boundaries will reduce grain boundary energy and thus stabilize the nanostructure. Electrodeposition has been found very promising in synthesis of ng metals, where additives are usually introduced to reduce grain size by moving the onset deposit potential negatively and consequent increasing the nucleation rate. In the electrodeposition of ng alloys, however, it is to be explored the effect of additives to the composition and the grain size of the synthesized ng alloy.

It is the purpose of the present work to explore the effect of additives (saccharin and 1, 4-butynediol) in the synthesis of ng Ni-Mo alloy film in aqueous citrate-ammonia electrolyte with different concentration of sodium molybdate (Na2MoO4·H2O) ranging from 0.5 to 7 g/L. The chemical composition of ng deposits were determined by Energy-dispersive X-ray spectroscopy (EDS). The microstructure of the synthesized ng Ni-Mo films were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) with the grain size determined by TEM dark field images. Voltammetry was employed to evaluate the effect of additives and also sodium molybdate to the deposition of Ni-Mo.

XRD results demonstrate that the as-deposited Ni-Mo films are all single fcc solid solutions. It is found Mo content in the deposits increases with the concentration of sodium molybdate in the electrolyte irrespective of the presence of additives. In addition, additives do not induce significant difference in the composition of the alloy deposits at a certain concentration of molybdate. The average grain size of the deposits decreases with the increase of sodium molybdate concentration from 44 nm to 5 nm corresponding to 0.5 g/L and 7g/L Na2MoO4·H2O respectively in plain solution, but the grain size reduces to 16 nm and 4 nm respectively in additives-added electrolyte corresponding to the same Na2MoO4·H2O concentration range. It is evident that saccharin and 1, 4-butynediol pronouncedly reduce the grain size of ng Ni-Mo when the Na2MoO4·H2O concentration is low but this reduction gradually gets small with the increase of molybdate concentration. Steady state polarization curves with the addition of additives and molybdate indicate an interaction between the saccharin, 1, 4-butynediol and the sodium molybdate, which correlates well with the composition and the characterized microstructure of ng Ni-Mo films.
Atom Probe Tomography of Dealloyed Materials
Authors: El-Zoka Ayman A. , Newman Roger C. , Langelier Brian
Published: February 2020

The high resolution characterization of nanoporous gold (NPG), a material with promising functional capabilities, facilitates better understanding of its structure-property relationships. An improved characterization of NPG by atom probe tomography (APT) was recently reported, using Cu electroplating to fill the pores [1]. Atomic scale analysis of nanoligaments showed the expected core-shell structure in high detail (Figure 1), confirming and extending previous findings using other characterization methods [2].

Further to those findings, finer, more complex nanoporous materials, formed by dealloying of AgAuPt alloys, have been studied by APT as well as STEM tomography, demonstrating an ever clearer 3D picture of the structure. As the extent of aberrations found in the data is directly related to the relative evaporation fields of the metals in the sample [3], further improvement of this technique prompts the search for alternative metallic fillers.

Figure 1- (a) Atom map of a single nanoligament in NPG formed by dealloying of Ag77Au23, (b) Chemical profiling across a single ligament.

References

[1] Ayman A. El-Zoka., Doug D. Perovic, Roger C. Newman, and Brian Langelier. "High Resolution Studies of Dealloyed Layers." In Meeting Abstracts, The Electrochemical Society, vol. 12, pp. 1259-1259, 2016.

[2] T. Fujita, P. Guan, K. McKenna, X. Lang, A. Hirata, L. Zhang, T. Tokunaga, S. Arai, Y. Yamamoto, N. Tanaka, Y. Ishikawa, N. Asao, Y. Yamamoto, J. Erlebacher and M. Chen, "Atomic origins of the high catalytic activity of nanoporous gold," Nature Materials, vol. 11, pp. 775-780, 2012.

[3] T.T Tsong, “Field ion formation,” Surf. Sci., vol. 70, pp. 211-233, 1978.

Figure 1
Electrochemical Nature of Silver Halide Underpotential Deposition on Au(111)
Authors: Phillips Jesse A. , Morgan Heather , Jackson Lauren E. , Jones Greg H. , Iski Erin V.
Published: February 2020

In previous research completed by Iski et al.1, it was found that through specific electrochemical methods, a silver (Ag) monolayer could be formed on a Au(111) surface in both a chloride-free and chloride-rich solution. The electrochemical method used was under potential deposition (UPD) and reduced Ag+ to the surface. The previous study showed that, in a chloride-free environment, the Ag monolayer could be formed and atomically resolved; however, once removed from the cell, it could be completely destroyed via hydrogen flame annealing. Interestingly, in the presence of chloride, the same Ag monolayer was formed and was found to be extremely thermally stable after removal from the cell and was resistive to temperatures as high as 1,000 K. The atomic structure of these films can be studied with electrochemical scanning tunneling microscopy (EC-STM), which not only allows for atomic scale imaging of the surface layer within an electrochemical environment, but also facilitates the taking of cyclic voltammograms (CVs), which can be used to examine the redox behavior of the systems. Through this electrochemical manipulation, a newly hypothesized mechanism for the reduction of AgCl to the surface rather than bare Ag+ ions is proposed. Despite many studies on these types of surface layers2, very few publications have directly studied their extreme thermal stability. Since it is known that the stability of bulk metal halide structures decreases as the halogen ion increases in size, an investigative study was performed following the same procedure, substituting chloride with bromide and iodide. As with the AgClx system, once AgBrx was used to form the Ag monolayer, a new surface structure formed which was also thermally resistive to a hydrogen flame. Conversely, the surface formed by the AgIx was not maintained and formed silver oxide insulating species after thermal treatment. CVs taken in the same region as those of the previous work show a definite surface modification by both AgBrx and AgIx before annealing which persists after the thermal treatment for the AgBrx. Further electrochemical studies into these Ag monolayers formed in a halogenated environment are being conducted in an attempt to better understand the properties of these surfaces and the type of redox chemistry occurring at the relevant potentials. Using EC-STM, we plan to study the ways in which this remarkable stability is imparted to the single crystal surface under ambient conditions.

[1] Iski, E. V. et al. Electrochimica Acta
2011, 56 (3), 1652–1661.

[2] Michalitsch, R.; Laibinis, P. E. Angewandte Chemie International Edition
2001, 40 (5), 941–94.
Synthesis and Characterization of Green Emitting Erbium Doped BaY2ZnO5 Nanophosphors
Authors: Taxak Vinod Bala
Published: February 2020

Green emitting Erbium doped photoluminescent nanophosphor for light emitting materials

V.B. Taxak1*, Sangeeta Chahar1

1Department of Chemistry, Maharshi Dayanand University, Rohtak -124001, India

*Corresponding Author: Tel: +919466722544

E-mail : v_taxak@yahoo.com

In this present era of nanotechnology, rare earth doped nanophosphors in nano dimension marks as thrust area of research owing to its magnificent characteristics like high lumen output, good color rendering index, high thermal stability and magnificent quantum efficiency involved with its unique optical behaviour. Due to the enhanced properties these nanomaterials are widely explored in the display devices like plasma display panels (PDP), field emission displays and light emitting diodes. Among the various RE3+ ions, Er3+
doped nanophosphors are widely explored on being the essential green component of the phosphor converted white LEDs because of green emitting luminescent properties. In this series, erbium activated oxide host matrix BaY2ZnO5 have found potential applications for luminescent phosphors on grounds of its magnificent electronic and magnetic properties, greater crystallinity. In present work, we are demonstrating the synthesis, properties and suitability of BaY2(1-x)Er2x
ZnO5 nanophosphors for the solid state lighting system in NUV excited PC-WLEDs. Erbium doped BaY2ZnO5 nanophosphor was successfully synthesized via sol-gel approach in nano dimension with particle size in 60-80 nm range as confirmed by transmission electron microscopy (TEM). The crystallinity of pure phased nanophosphor in orthorhombic lattice with Pbnm (62) space group was confirmed through X-ray diffraction analysis. On excitation at 380 nm (4I15/2→ 4G11/2 transition) the nanophosphor yields green emission at 549 nm attributed to 4S3/2→ 4I15/2 transition with optimum concentration for maximum luminescence was 4 mol%.
Dissolution and Shape Controlling of Crystalline ZnO
Authors: Chung Ji Yong , Yu Taekyung
Published: February 2020

ZnO is a one of most promissing material that has many attractive chemical and physical properties. ZnO is direct-bendgap semiconductor with a large bandgap of 3.37 eV, also it has strong exciton binding energy and it usually has high electron mobility.

For this reason, It had widely used to light-emitting diodes, solar cells and sensors. Nowaday, demand of high performance device is much stronger, so many researcher enhance these properties to nanotructure as a necessity.

we introduce new way to control shape of ZnO in nanoscale.
Aqueous-Phase Synthesis of Metal Nanoparticles Using Phosphates As Stabilizers
Authors: KIM Inho , Yu Taekyung
Published: February 2020

In this paper, we describe a simple, aqueous-phase route to the synthesis of metal nanoparticles including Pt, Pd, Ru, and Au based on the aqueous-phase reduction of metal salts with NaBH4. In this approach, various phosphates were applied as new type of stabilizers for the synthesis of metal nanoparticles thanks to its negatively charged functional group (PO−).
Newly Introduced Green Solvent for Organic Photovoltaics Processing
Authors: Farhat Mahmoud , Chu Chih-Wei
Published: February 2020

A new green solvent, cyclopentyl methyl ether (CPME), has been applied to replace toxic chlorinated solvents in the production of efficient molecular photovoltaics. We employed a conjugated small molecule (SMPV1) as donor and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as the acceptor in solar cell devices. Using CPME-only as the host solvent, power conversion efficiency (PCE) of 3.13% was achieved. The low PCE came from the low PC61BM solubility in this green solvent. Accordingly, we introduced toluene (Tol) in different amounts as a co-solvent for CPME. The greater solubility of PC61BM in these mixtures led to significant improvements in the short-circuit current density and fill factor of the device, achieving a PCE of 7% after processing in the optimized green solvent mixture of CPME:Tol. Thermal annealing (TA) of the active layers processed from the optimized green solvent mixture enhanced the PCE to 8.10%. This efficiency is the highest reported for a molecular solar cell processed from a green solvent mixture to date. Large-scale devices fabricated this way, having areas of 1 and 5.5 cm2, exhibited PCEs of 6.20 and 3.73%, respectively. The morphological changes that occurred when applying the co-solvent and TA played key roles in achieving such high PCEs. This work paves the way toward organic photovoltaics scaling up using green solvents.
Raman Mapping and Delineation of III-V Semiconductor Band Bending Characteristics
Authors: Lichterman Michael Frankston , Carim Azhar I , Brunschwig Bruce S , Lewis Nathan S
Published: February 2020

Raman spectroscopy has previously been used to ascertain the nature and extent of band bending at III-V semiconductor interfaces. Many previous investigations have focused on samples cleaved in vacuum and subsequently exposed to oxygen gas or a thin metal deposition; generally, specific polarizations of incident and scattered light are applied and collected in order to specify and isolate the desired phonon peaks under investigation1,2. We demonstrate herein a more general and easily applied method to investigate III-V interfaces by Raman spectroscopy using analysis of the longitudinal optical (LO) and transverse optical (TO) phonons; furthermore, we provide a means by which the ratios resulting from such experimentation may be normalized. Interfaces can be deeply buried under tens or hundreds of nm of material and still be investigated, unlike the case with photoelectron spectroscopy; furthermore, this technique can provide electronic mapping of such interfaces with micron sensitivity.

References

1. Geurts, J., Analysis of band bending at III–V semiconductor interfaces by Raman spectroscopy. Surf. Sci. Rep.
1993,
18(1–3), 1-89.

2. Srnanek, R. et al. Study of δ-doped GaAs layers by micro-Raman spectroscopy on bevelled samples. App. Surf. Sci. 2004, 230, 379-385.