bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Fracture Mechanics of Ionic Conductors By Internal Precipitation
Authors: Virkar Anil V.
Published: February 2020

Ceramics are currently being used in many electrochemical energy conversion and storage systems. These include solid oxide fuel cells (SOFC), solid oxide electrolyzer cells (SOEC), oxygen separation membranes, hydrogen separation membranes, synthesis of gaseous and liquid fuels by electrolysis, alkali metal batteries and alkali metal thermoelectric generators, to name a few. These devices are based on either anion conducting electrolytes or cation conducting electrolytes. The devices operate over a wide range of temperatures, from room temperature to 1000oC, and under harsh environmental conditions. Fundamental physical, chemical and mechanical properties, which can depend upon materials composition and microstructure, dictate the durability of these materials in the applications environment. A unique attribute is that small changes in electrochemical properties can substantially influence their mechanical durability. Failure of these materials in applications often involves fracture or delamination, similar to many applications of structural ceramics in engineering applications. Yet, the mode of failure is almost always quite different from that typically encountered in applications involving structural ceramics. For example, in electrochemical systems failure often involves slow crack growth under electrochemical device operating conditions. Failures often occur by the precipitation of electrically neutral species corresponding to the mobile ion. The precipitated neutral species may be an electrical insulator (oxygen gas) or an electrical conductor (lithium or sodium metal). The mode of failure is very different in the two cases. The role of physical, chemical and electrical properties on durability of such ceramics in electrochemical systems will be discussed and contrasted with applications in which the load is purely mechanical. Fracture mechanics under remote load will be compared and contrasted with fracture mechanics under internally generated loads. Experimental results will be presented on oxygen ion conductors.
Colloidal Syntheis of Ptzn Nanocrystals and Their Activity for Oxygen Reduction Reaction
Authors: Ye Youngjin , Lee Jinwoo
Published: February 2020

Commercialization of a polymer electrolyte fuel cell (PEMFC) is confronted with insufficient activity and durability of Pt-based cathode catalyst. Therefore, catalyst development for oxygen reduction has been focused on the increase of the specific activity of Pt-based catalysts by alloying Pt with transition metals. Computationally based electrocatalyst screening has made it possible to reduce the efforts for finding cathode catalysts with high activity and durability. According to the computationally predicted oxygen binding energy for Pt-based alloys, Pt3Zn has the nearly optimal oxygen binding energy for oxygen reduction.1 However, there is still lack of information on Pt3Zn as a cathode catalyst in a PEMFC. Here, we synthesized uniform Pt-Zn nanoparticles in oleylamine that has an average size of 4 nm. After deposition of Pt-Zn nanoparticles on a carbon support, the resulting material was heat-treated at higher than 400 oC. The electrocatalytic properties of Pt-Zn nanoparticles and the heat-treatment effect will be presented.

[1] J. Greeley et al. Nature Chemistry
2009, 1, 552.
Synthesis of TiO2 Nanotubes By Ti Foil Electrochemical Dissolution
Authors: Nikoleishvili Paata , Kurtanidze Rusudan , Gorelishvili Giorgi , Kveselava Valentina , Sharabidze Davit , Gogoli Davit
Published: February 2020

The growing demand for environmentally clean energy because of depletion of fossil fuel resources and the issues of climate change, such as global warming, caused the need for environmentally stable sources of energy. Renewable energy can be obtained from stable resources. Solar energy has the large prospects as an alternative source of energy, because its feed is un-limited and free. 

Goal of the project is the preparation of TiO2 nanoparticles for dye-sensitized photoelectrochemical solar cell. We propose a new method of TiO2 electro-generation. TiO2 nanoparticles have been obtained by Ti foil anodic dissolution in 0.1-1M HCl solution, where hydrogen peroxide solution (30%) drop by drop has been added, cathode was stainless steel foil, and current density in different tests has been changed from 0.2 A/cm2 to 1A/cm2, voltage has been changed from 8 V to12 V, respectively. Electrochemical processes have been carried out at 90oC at steering rate 800 rpm. TiO2 has been directly obtained in electrolyte solution. This method gives allows to control a size of generated TiO2 particles by changing current density and hydrogen peroxide addition rate. TiO2 nanoparticles have been identified by X-ray diffraction (XRD) and scanning electron microscope (SEM) with particle size 50-500 nm. Finally, dye-sensitized photoelectrochemical solar cell has been fabricated. 

Electrochemical properties of the solar cell (i-V and I-P  curves): open circuit voltage 0.63 V, short circuit current  12 mA/cm2, maximum power 4 mW/cm2 and current density at the maximum power - 7.5 mA/cm2, fill factor (ff) - 0.538, light energy conversion efficiency - 8.0%.
Fabrication and Electrochemical Properties of Highly Ordered Titania Nanotubes Modified with Boron Nanocrystalline Diamond
Authors: Bogdanowicz Robert , Siuzdak Katarzyna , Sobaszek Michal , Szkoda Mariusz
Published: February 2020

Recently, we reported on the phenomena of the formation of the novel composite material based on titania nanotubes (TiO2 NTs) over-grown by thin boron-doped diamond (BDD) produced in microwave plasma enhanced chemical vapor deposition (MW PE CVD) [1,2]. Under microwave plasma treatment, the structure TiO2 NTs underwent transformation from stoichiometric anatase into non-stochiometric oxide with Ti(III) phase and some rutile phase arises. Furthermore, obtained material was characterized with a significantly enhanced conductivity and capacitance comparing to pristine titania. The electrochemical studies showed that the specific areal capacitance of TiO2/BDD raised up to 7.46 mF cm-2 whereas for the pure BDD it reached only 0.11 7.46 mF cm-2.

Because of such strong modification of titania and application potential in energy storage devices we decided to initiate growth of boron nanocrystalline diamond (B-NDC) on the highly ordered TiO2 nanotube arrays. TiO2 NTs are fabricated via two-step anodization of titanium metal plate followed by a short immersion in diluted HF in order to remove any surface debris [3]. Titanium plate covered by uniform titania nanotube layer provides a large specific surface area as well as a direct pathway for charge transport, thus holding promising capabilities of being support for another materials deposition. Afterwards, similarly to formation of TiO2NTs/BDD material, the deposition of boron nanocrystalline diamond will be also realized under microwave plasma conditions and Ti/TiO2 NTs will act as a substrate. The morphology and the structure of obtained composite material will be investigated using scanning electron microscopy and Raman spectroscopy. Electrochemical activity will be identified applying cyclic voltammetry and electrochemical impedance spectroscopy techniques performed in aqueous electrolyte. The influence of boron-doping level will be observed as a change in registered capacitive current and impedance behaviour.

References:

[1] K. Siuzdak, R. Bogdanowicz, M. Sawczak, M. Sobaszek, Enhanced capacitance of composite TiO2 nanotube/boron-doped diamond electrodes studied by impedance spectroscopy, Nanoscale 7 (2015) 551

[2] M. Sawczak, M. Sobaszek, K. Siuzdak, J. Ryl, R. Bogdanowicz, K. Darowiski, M. Gazda, A. Cenian, Formation of highly conductive boron-doped diamond on TiO2 nanotubes composite for supercapacitor or energy storage devices, J Electrochem Soc 162 (2015) A2085

[3] M. Szkoda, K. Siuzdak, A. Lisowska-Oleksiak, J. Karczewski, J. Ryl, Facile preparation of extremely photoactive boron-doped TiO2 nanotube arrays, Electrochem Comm. 60 (2015) 212

Financial support from the Polish National Science Center – under grant No. 2012/07/D/ST5/02269 and No. 2011/03/D/ST7/03541 is gratefully acknowledged.
Vulcan/Pt/Ce(III) Catalysts Prepared By Impregnation Using EDTA for Direct Methanol Fuel Cell, and Direct Ethanol Fuel Cell Applications
Authors: Guzmán-Blas Rolando P , García-Herrera Yaileen , Lotti-Díaz Leilani , Ocasio-Norat Krystel
Published: February 2020

Cerium modified Pt nanoparticles catalysts have been prepared using Ce(III)-ethylenediamine-tetraacetic acid (EDTA) chemistry with an impregnation method of 30%Pt/Carbon Vulcan XC-72. EDTA was used as a chelating agent to form a Ce(III) complex to achieve good dispersion of ceria on Pt/C while maintaining +3 oxidation state. Different compositions of Ce(III) with Pt/C have been examined to optimize the catalyst material. The methanol and ethanol oxidation studies were performed using the GC electrode previously modified with Vulcan-Pt and Vulcan-Pt-Ce(III). The catalytic activity toward methanol and ethanol oxidation for the different electrodes was performed using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry with a 1.0 M CH3OH solution in 0.5 M H2SO4 and, for ethanol, a 1.0 M C2H5OH solution in 0.5 M H2SO4. The catalyst samples were characterized by using the characterization technique of X-ray diffraction. It has been found that the catalytic activity of Ce(III)/30wt%Pt/C exhibited better activities than 30wt%Pt/C in direct methanol fuel cell and direct ethanol fuel cell. A Vulcan-Pt-Ce(III) doped catalyst was prepared by a simple and cheap impregnation method using EDTA as chelating agent. The preparation method will allow the mass production of the material catalysts without additional significant cost.
Gold-Cobalt Deposited on Titania Nanotubes as Anode Catalyst for Direct Borohydride Fuel Cells
Authors: Santos Diogo M.F. , Balciunaite Aldona , Tamasauskaite-Tamasiunaite Loreta , Zabielaitë A. , Jagminienë A. , Stankeviciene Ina , Norkus E.
Published: February 2020

In the present work gold-cobalt catalysts deposited on titania nanotubes surface (denoted as Au(Co)/TiO2-NTs) were investigated as anode material in direct borohydride fuel cells (DBFCs). The catalysts were prepared by a simple and cost-effective galvanic displacement technique [1]. At first, the sub-layer of Co was deposited on the titania nanotubes surface via electroless deposition. The gold crystallites were then deposited on the Co/TiO2-NTs electrodes by their immersion into gold(III)-containing solution for different time periods. It has been determined that the Au loadings were in the range from 10 to 60 µg cm–2 in the Au(Co)/TiO2-NTs catalysts.

Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDXS) were used to characterize the surface morphology and composition of the samples, respectively. The activity of the Au(Co)/TiO2-NTs catalysts for borohydride oxidation reaction (BOR) was evaluated by cyclic voltammetry and chronoamperometry measurements.

The performance of a DBFC operating with 1 M NaBH4 + 4 M NaOH as fuel and 5 M H2O2 + 1.5 M HCl as oxidant, while employing Pt as the cathode catalyst and Au(Co)/TiO2-NTs with different Au loadings as the anode catalyst were investigated. Peak power densities up to 122 mW cm-2 were attained at 25 ºC. It was found that the highest specific peak power density of 9.6 kW g–1
Au was obtained when employing Au(Co)/TiO2-NTs with the Au loading of 10 µg cm–2as the anode catalyst.

References

[1] L. Tamašauskaitë-Tamašiûnaitë, A. Jagminienë, A. Balèiûnaitë, A. Zabielaitë, A. Þielienë, L. Naruškevièius, J. Vaièiûnienë, A. Selskis, R. Juškënas, E. Norkus. Int. J. Hydrogen Energy 38 (2013) 14232-14241.

Figure 1
(Invited) Functional Gradient Carbon-Sulfur Cathode for Rechargeable Li-S Battery
Authors: Liu Xingbo , Yan Jianhua , Yao Meng , Li Bingyun
Published: February 2020

Lithium−sulfur (Li−S) battery is promising next generation rechargeable battery due to its potential high energy density. However, it suffers from major problems including poor cycle performance and low efficiency, mainly due to the high solubility of intermediate poly-sulfides and their side-reactions with the Li-anode.  Recently, we have developed various open-structure functional gradient C-S composite cathodes with very high S-loadings that can utilize the high energy density of S-cathode while minimize the migration of poly-sulfide to anode side. We employed scalable and industrial viable method such as layer-by-layer nano-assembly technique that leads to a binder-free, three-dimensional porous cathode via electrostatic attraction and enables the fabrication of Li−S cells with remarkably improved performance including a long cycle life exceeding 600 cycles and a high Coulombic efficiency of 97.5% at the 1 C rate. Moreover, our Li−S cells have presented a high rate response up to 2.5 C with high sulfur utilization (a reversible capacity of 1100 mAhg−1, 900 mAhg−1, 700 mAhg−1, and 450 mAhg−1 of sulfur at 0.3, 0.6, 1, and 2.5 C rates, respectively). The results provide important progress toward the understanding of the role of multilayered cathodes and the realization of high-efficiency and long-term service life for Li−S batteries.
Nanoscale Interfacial Interaction of Polysulfide with Porous Metal Oxides
Authors: Vijayakumar Murugesan , Prabakar Kandasamy , Dissanayake Amila , Bhattacharya Priyanka , Han Keesung , Mueller Karl T
Published: February 2020

Sulfur is a promising cathode for high energy density lithium-sulfur battery, but plagued by polysulfide dissolution causing loss of active material and detrimental parasitic reactions. In recent years multiple strategies have been employed to address the parasitic reaction of polysulfide species and increase the life cycle of the Li-S battery. One of the main approaches is employing porous materials as internal reservoirs which can absorb/desorb polysulfides during electrochemical cycling and thereby prevent the shuttling process. Despite intensive efforts to design optimal reservoir materials, the progress in this field is dragged by the knowledge gap in terms of molecular level view about polysulfide interaction with host material. We studied the interaction of polysulfide species including highly reactive trisulfide free radicals with porous silica and alumina metal oxide nano-particles The polysulfide interaction with metal centers of nano-particles are analyzed using combined experimental spectroscopic studies (magnetic resonance and X-ray absorption spectroscopy) and density functional theory based computational methods. This work provides molecular level insight about polysulfide reactivity on metal oxide surfaces which can help in understanding the emergent behaviors of hetrogeneous interfaces.
(Invited) High Rate Energy Storage Based on Pseudocapacitance in Oxide Materials
Authors: Dunn Bruce
Published: February 2020

The growing interest in using pseudocapacitor-based materials for electrochemical energy storage is that the energy density associated with faradaic reactions is much greater, by at least an order of magnitude, than the electrical double layer capacitance of carbon electrodes. The reversible redox reactions that characterize pseudocapacitance occur at or near the surface of an electrode material and are fast enough so that the device's electrochemical features are similar to those of a carbon-based capacitor, but with significantly higher energy density. This paper will review recent research directed at identifying various electrochemical and structural characteristics which provide insight regarding pseudocapacitive materials and properties.  One key feature associated with pseudocapacitance is that the rate of charge storage is determined by surface-like kinetics rather than semi-infinite diffusion as occurs with battery materials. In this regard, the presence of two-dimensional pathways in the structure of the oxide material seems to be favorable for obtaining a pseudocapacitive response. Another important consideration with this mechanism is that the structure does not undergo a first-order phase transition upon Li+ insertion. However, even with materials that exhibit such phase transitions, nanostructuring the material can effectively suppress the structural change and lead to attractive properties. In the case of nanoscale MoO2, we showed that pseudocapacitive properties are developed which enable the material to operate at high charge/discharge rates without decreasing the level of charge storage.  Morphology is another parameter that can be used to develop pseudocapacitive properties in oxides.  Mesoporous materials, which possess an interconnected pore network that provides electrolyte access to thin (<15 nm) redox-active walls, lead to a pseudocapacitive response while two-dimensional nanosheets of transition metal oxides exhibit surface-controlled kinetics indicative of pseudocapacitive behavior. The ensemble of these results suggests that we can expect an increasing number of materials to be developed that retain high energy density at charge/discharge rates which are well above those of battery materials.
Microsomal Bioelectrodes Modified with Nanostructures for Rapid Drug Metabolism and Inhibition Assays and Cost-Effective Green Synthesis
Authors: Krishnan Sadagopan , Walgama Charuksha , Nerimetla Rajasekhara
Published: February 2020

Purification of membrane-bound enzymes in general and drug metabolizing human liver cytochrome P450 heme enzymes (CYPs)[1] in particular has been a major bottleneck in advancing the field of enzyme electrocatalysis. The ability to use unpurified enzymes and additionally mimic in vivo drug metabolic pathways would accelerate current drug development processes by enabling cost-effective rapid electrochemical drug screening and stereoselective drug metabolite synthesis. For new drug development, human liver microsomes (HLMs) are being used as in vitro systems to study drug metabolism, inhibition, and drug-drug interactions and to identify the specific isoforms of CYPs involved in these processes.[2] Application of liver microsomes or genetically engineered versions of microsomes containing CYPs and CYP-reductase in the development of new biosensing and electrocatalytic systems is an emerging research area.[3] Recently, our laboratory examined the influences of various carbon electrode materials in the direct electron transfer and electrocatalytic properties of immobilized HLMs.[4] We found that electrode roughness and hydrophilic nature offered greater electrocatalytic currents and microsomal film stability on electrodes. As a next step, our goal is to achieve highly enhanced electrocatalytic metabolite production with sufficient electrocatalytic stability and reusability features. For this, we are exploring various nanotechnology strategies to immobilize microsomes in biologically active form.  Results from our preliminary findings in this objective utilizing carbon and metal oxide nanomaterials will be discussed.

[1] P. R. Ortiz de Montellano, Future Med. Chem. 2013, 5, 213-228.

[2]  L. C. Wienkers, and T. G. Heath, Nat. Rev. Drug Discov. 2005, 4, 825-833.

[3] S. Krishnan, J. B. Schenkman, and J. F. Rusling, J. Phys. Chem. B 2011, 115, 8371-8380.

[4] C. Walgama, R. Nerimetla, N. F. Materer, D. Schildkraut, J. F. Elman, and S. Krishnan, Anal. Chem.
 
2015
, 87
, 4712-4718.
Quasireversible Is Irreversible Dressed up
Authors: Harrington David A.
Published: February 2020

Diffusion and convection to an electrode with an irreversible reaction is allegedly a much simpler mass-transport problem than the same problem for a quasireversible reaction. This seems self-evident, since in the quasireversible case the mass transport of the product species has to be included, not just the reactant species. This leads to a coupled mass transport problem, and that has to be harder, right? Well, not necessarily. Under the common assumption that the diffusivities are equal, the quasireversible concentration profiles and current density can be trivially derived from the irreversible ones. One just replaces the forward rate constant by the sum of the forward and backward rate constants, scales the result and adds a constant. What could be simpler than that?

I show that this works under most of the convective diffusion situations encountered in electrochemistry. Of course there are some restrictions. On the other hand, for some cases the condition of equal diffusivities can be relaxed. I give some examples of where this is more than just a curiosity in relating known results in classic electrochemistry. In particular, it can lead to more efficient numerical analysis schemes.

[1] D.A. Harrington, Electrochim. Acta., 308, 152 (2015).
Dye-Sensitized Solar Cells in Humidity Environment: A Suitable Fabrication Procedure and Outdoor Test of Cell Stability
Authors: Nguyen Hoang Thai , Tran Linh Thi Phuong , Le Nghiem Van , Vo Long , Nguyen Thoa Thi Phuong
Published: February 2020

The performance of dye-sensitized solar cells (DSCs) fabricated by conventional procedure in humid environment have rapidly declined in outdoor testing. This fact may be caused due to the uptake of water into cells during the process of dye soaking (around 20 - 24 hours) and electrolyte filling under ambient air. In this work a new fabrication procedure, that proved to prevent the water uptake, was established for DSC assembling in high humidity environment. In the procedure, the sandwich cell, assembled from preparative FTO/TiO2 and FTO/Pt electrodes was filled with N719 (10 mM)/DMF solution for the dye adsorption on TiO2film in 4 hours. The dye adsorbing, electrolyte filling and cell sealing have been carried out in inert gas atmosphere using a glove box.

By new fabrication procedure the energy conversion efficiency (η) of DSCs was improved on 10%. In addition, DSCs fabricated by new procedure were more stable under outdoor testing, the efficiency was even increased 9% at 14-day-outdoor-exposure. From 30thday of outdoor test the cell efficiency began slightly decrease, and reached the  initial value after 100-day-exposure.

The effect of co-adsorption with chenodeoxycholic acid (CDA) on DSC performance based on new fabrication procedure was investigated. By addition of 100 mM CDA the short circuit photocurrent has significantly increased, the open circuit voltage slightly increased, and the overall power conversion efficiency of as-prepared DSCs was improved by 8%. However the effect of CDA on cell performance was diminished during outdoor exposure.

The change of DSC characteristics was discussed based on analysis of electrochemical impedance spectroscopy (EIS) data. The enhancement of photocurrent caused by the photo-activation of the cathode interface during first weeks of outdoors exposure, as well was the effect of co-adsorbate, were interpreted from impedance spectra.
Modified TiO2 Nanotubes for Photoelectrochemical (PEC) Water Splitting Applications
Authors: Aljohani Talal Awad
Published: February 2020

Titanium oxide nanotubes (NTs) were synthesised using the electrochemical anodisation approach in a glycerol-based solution containing NH4F at 10 volts. Pulse electrodeposition (PED) was applied to decorate the NTs with copper. The results reveal that the morphology of the porous nanotubes plays a significant role in the efficiency of photoelectrochemical water splitting. The highest photocurrent density obtained is 5.77 mA cm-2 at 1.23 V vs. RHE for the annealed pure TiO2 nanotubes (NTs) illuminated with a solar simulator under visible light (ʎ≥ 385 nm). The Cu doped TiO2 nanotubes showed lower photocurrent density compared to the pure TiO2 nanotubes (NTs) despite an increase in the carrier density (ND) concentration after Cu doping. The maximum photon conversion efficiency achieved is 1.1 % at 1.23 vs. RHE, which is the highest conversion efficiency ever reported under such conditions.

Figure 1
Comparison of Molecular-Wires for Enhancing Charge Transport of Enzymatic Electrode Assemblies: A Glycerol Bioanode Model
Authors: Mahadevan Aishwarya , Fernando Sandun
Published: February 2020

Biomolecules are inherently less conductive. Therefore, bio-electronic devices that depend on conventional biomolecules to tether enzymes onto electrode supports and to shuttle electrons between the enzyme and the electrode suffer from charge dissipation. This results in bioanondes with decreased current-voltage responses as a result of ohmic losses. Thus, lack of an effective molecular wiring system that can allow unimpeded charge transport is a significant problem that hinders our ability to utilize the full potential of enzymatic self-powering bioelectronic devices. Reducing the internal resistance is the simplest way of increasing the current-voltage response associated with bioanodes and has yet been an unmet challenge. In living cells, iron-sulfur complexes ([Fe-S]) are known to aid in circumventing these issues in the mitochondrial electron transport chains. We describe a technique to attach iron-sulfur moieties to gold surface in non-aqueous media initially and then continue coenzyme and apoenzyme attachment in aqueous media while keeping the efficacy of FeS and the enzyme system intact. As a working model, a glycerol-sensitive gold bioanode is described based on direct attachment of the glycerol-dehydrogenase (GlDH)-NAD+ apoenzyme-coenzyme complex onto the supporting gold surface using iron (II) sulfide (FeS) mediation. A conventional pyrroloquinoline quinone (PQQ)-based electrode was used as the control. The performances of the two electrode systems were compared using amperometric and potentiometric studies. Successful tethering of the molecular wiring schemes was verified using cyclic voltammetry and spectroscopy. Amperometric and potentiometric analyses with glycerol dehydrogenase-based model electrodes confirmed the ability of this single-molecule to remarkably amplify, about ten-fold increase in current and up to 24% increase in voltage outputs, as compared to electrodes fabricated with the conventional PQQ-based composite molecular wiring system. FeS achieves the dual purpose of anchoring the enzyme to the gold electrode while also mediating electron shuttling between coenzyme and the electrode surface. This dual functionality allows usage of a single-molecular wire to foster electrical communication between the enzyme and the electrode instead of the conventional multi-molecular wiring system and in turn reducing the internal resistance of the electrode. The resulting increase in current/voltage response opens up a wide range of possibilities for developing efficient bio-electrodes for bioelectronics applications. The importance of this work is the ability to reduce the internal resistance (and thus the overpotential) of circuits that use redox enzymes - allowing complete utilization of the “available power” and “signal capacity” in enzyme-based bioelectronic systems.
Effect of Morphology Controlled Synthesis of BiOCl Photocathode By Chemical Vapor Deposition for Solar Water Reduction
Authors: Myung Yoon , Banerjee Sriya , Banerjee Parag
Published: February 2020

Bismuth oxychloride has emerged as an important material for photoelectrochemical, photocatalysis and photovoltaic application. Its unique crystal structure of alternating sheets of [BiO2]2+ and two Cl-1 along the c-axis, leads to the formation of an internal electrical dipole, facilitating faster electron-hole separation. It has a p-type conductivity with a bandgap of ~3.4 eV and its band edge position is suitable for photelectrochemical water reduction.

In this study, BiOCl films with 3 different morphologies are synthesized by the chemical vapor deposition process and the effect of sample morphology on the photoelectrochemical behavior is studied. BiOCl is deposited on transparent electrodes by thermal vapor transport of BiCl3 precursors. Figure 1(a-c) shows the as deposited microwall, micropore and microflower morphologies of BiOCl, obtained by finely controlling the deposition conditions

The photoelectrochemical cells fabricated using the as grown micropore morphology showed the highest photocurrent. The micropore structure allows solution penetration into the pores thus providing faster charge transport pathways. Structural investigation will be presented using SEM, XRD and Raman spectroscopy. This work demonstrates that tailoring the BiOCl surface morphology can lead to efficient photoelectrochemical water reduction.

Figure 1
Electrochemistry of Co(TPTZ)2 Complex on a Carbon Paste Electrode Modified with TiO2 Nanoparticles
Authors: Ortaboy Sinem , Atun Gülten
Published: February 2020

Nowadays, the cobalt based complexes have attracted considerable interest in dye sensitized solar cells (DSSC). They have been widely used as a redox electrolyte [1], sensitizing agent [2] and the component of counter electrode (CE) material [3]. Therefore, their electron-proton transfer behavior should be taken into account to achieve success in efficient DSSC [4].

In the present study, electrochemical behavior of cobalt (II) complex with the N-donor ligand 2,2’-bipyridyl-1,3,5-tripyridyl-s-triazine (TPTZ) on the TiO2 modified carbon paste (T/CPE) was compared with the bare carbon paste electrode (CPE). The electrochemical response of the complex was studied by means of square-wave voltammetry (SWV) technique in a conventional one compartment cell using a saturated Ag/AgCl and a platinum wire as the reference and counter electrode, respectively. The effect of TiO2/graphite ratio of T/CPE on the voltammetric response of the Co(TPTZ)2 complex was examined and the best result was obtained for 60 % (w/w). The ligand/metal ratio and stability constant of the complex as well as the mechanisms of the electrode processes were elucidated by examining the effects of pH, ligand concentration and frequency on the voltammograms. The optimum pH was selected as 7.5 for comparison of the T/CPE and CPE electrodes. The electrochemical impedance spectroscopy (EIS) results obtained in the phosphate buffer indicated that T/CPE had higher charge transfer resistance and electroactivity than those of the bare electrode. It was concluded from the Bode-phase diagrams that nano-TiO2 structure increases the conductivity between electrode and electrolyte interface due to the good penetration of the Co(TPTZ)2 complex into the electrode surface trough the nano-TiO2 pores. All the electrochemical results were found to be consistent with the surface morphology of the working electrodes obtained using atomic force microscopy (AFM).

References:

[1] T.W. Hamann, Dalton Transactions 41 (2012) 3111–3115.

[2] N. Goswami, P. K. Gogoi, M. K. Bhattacharyya, D. Saikia, International Journal Of Innovative Research & Development 1 (7) (2012) 92-103

[3] S.Y. Chae, Y.J. Hwang, J.H. Choi, O.S. Joo, Electrochimica Acta 114 (2013) 745– 749.

[4]S. Ortaboy, G. Atun, Materials Chemistry and Physics 156 (2015) 129-140

Acknowledgements

This work was supported by Scientific Research Projects Coordination Unit of Istanbul University. Project Number: 3757-Doctoral Thesis Project. It was also supported by the Scientific and Technological Research Council of Turkey (TUBITAK) 2219- International Postdoctoral Research Fellowship Program (App. No: 1059B191401401).
Catalyzing Hydrogen Evolution Reaction By the Use of Earlier Transition Metal Nitrides
Authors: Abghoui Younes , Skulason Egill
Published: February 2020

Today’s society is in pursuit of an alternative route for production of energy and chemicals due to scarcity of natural gases and fossil fuels. At the same time, strict environmental regulations push international scientific and industrial community towards more sustainable ways to meet the increasing demands of our energy-intensive society resulted in development of energy conversion technologies. As of now, hydrogen is accepted as an integral ingredient for renewably synthesis of e.g. ammonia and methanol. It is also the cleanest fuel and one of the most promising sources of energy [1]. The electrochemical hydrogen evolution reaction (HER) is a very interesting CO2-free approach effectively catalyzed by the Pt group metals. But Pt is scarce and therefore expensive. In order to meet the increasing need for hydrogen and energy, new catalysts should be explored that are active for HER as good as or nearing that of Pt fulfills. If that achieves, precious Pt can be replaced by cheaper and more abundant material holding great promise for clean energy technologies.

In this study, we used density functional theory calculations to screen for highly stable and active catalysts amongst a range of transition metal nitride surfaces [2]. The free energy of all intermediates was calculated with density functional theory (DFT). For the candidates promising for HER, activation energies for H2 formation were calculated at varying applied potentials [3]. The free energy of adsorption of H nominates a few nitrides capable of catalyzing HER at low overpotentials of around 0.0 to +0.35 V vs. SHE. We are currently examining these extremely promising HER catalysts in more detailed theory and experiment and the preliminary observations and measurements are indicative of the validity of our model as the proposed overpotentials for HER agree with the experimental polarization curves.

References

1) Crabtree, G. W., Dresselhaus, M. S. and Buchanan, M. V. Phys. Today, 2004, 57, 39−44

2) Y. Abghoui, A. L. Garden, V. F. Hlynsson, S. Björgvinsdóttir, H. Ólafsdóttir, and E. Skúlason, Phys. Chem. Chem. Phys., 2015, 17, 4909–4918.

3) Y. Abghoui and E. Skúlason, in preparation (2015)

Figure 1
Color Tests and Electrocanalytical Methods for the Preliminary Identification of Drugs
Authors: Miecznikowski Krzysztof , Kulesza Pawel J , Ordak Michal , Jedral Wojciech , Bulska Ewa , Grela Karol , Kosnik Wioletta , Bachlinski Robert , Duszynska Anna , Trynda Anna
Published: February 2020

In the literature various chemical reagents have been developed during the past century that are suitable for the preliminary identification of different illicit drugs such as Marquis, Liebermann’s, Simon’s. Color tests are an important tool for the preliminary identification of illicit drugs in spite of developments in instrumental technology and the increased portability of this technology which enables its use in the field. Color tests or spot tests are chemical tests that involve the reaction of a sample with a reagent or a series of reagents to produce a color or a change in color. The popularity of color tests arises from the fact that they are generally simple, quick, inexpensive, and quite sensitive. They are readily available and require minimal materials. These factors enable color tests to be used in the field and can be employed by those without extensive chemical backgrounds. A negative result for a color test is helpful, for instant in excluding a drug or class of drugs, depending on the test performed. In this study, we are going to describe a concept of utilization of various Keggin-type heteropolyacids of molybdenum and tungsten as suitable reagents for the preliminary identification of suspected illicit drug samples. Heteropolyacids of molybdenum and tungsten will be used as solution (spot test) as well as strip test for the screen identification of illicit drug samples. Moreover, the electroanalytical diagnostic experiments and ATR-FTIR measurements have been also utilized for identification of various illicit drugs.
Effects of Composition and Structure on Performance and Durability of Pt-Ni Extended Surface Catalysts
Authors: Pylypenko Svitlana , Ngo Chilan , Shulda Sarah , Alia Shaun M , Pivovar Bryan S
Published: February 2020

Reduction of electrocatalyst costs is crucial to the commercialization of proton exchange membrane fuel cells (PEMFCs). Platinum nanoparticles on high surface area carbon (Pt/HSC) substantially increase the Pt surface area and thus decrease the required amount of Pt, but suffer from loss of activity from various degradation processes. Extended Pt nanostructures are promising candidates to replace traditional electrocatalysts, as they have been shown to improve specific activity and durability; however, these materials have typically exhibited limited surface areas.

In this work, extended surface Pt-nickel (Ni) nanowires with 7 and 17 wt% Pt have been synthesized via spontaneous galvanic displacement and achieved exceptionally high surface areas (up to >90m2/g Pt). Various post-processing treatments have been applied to modify the composition and structure of these nanowires, with the goal of further improving their activity and durability. Extensive spectroscopy and microscopy studies were carried out to elucidate relationships between electrochemical performance and material composition, morphology, and structure both in bulk and at the surface.

Annealing the Pt-Ni nanowires in hydrogen continuously increased the specific activity with a peak in mass activity at 250°C. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) show that this activity increase is a result of Pt-Ni alloying. An additional cause of the increased activity is likely the formation of a more homogeneous Pt layer, which was induced by hydrogen annealing and clearly visible in elemental maps aquired with energy dispersive x-ray spectroscopy (EDS) via transmission electron microscopy (TEM). Further modification of the hydrogen annealed samples discussed in this work include oxygen annealing, acid leaching, and combinations of acid leaching with further heat treatments. XPS, TEM and EDS were used to investigate changes in the nanowires resulting from different strengths of acid treatments, which were utilized to remove undesired Ni species while maintaining high activity and durability.

[1]. S.M. Alia, Y. Yan, B.S. Pivovar, “Galvanic Displacement as a Route to Highly Active and Durable, Extended Surface Electrocatalysts” Catalysis Science and Technology, 2014, 4 (10), 3589 - 3600. DOI: 10.1039/C4CY00736KG.

Figure 1. EDS maps of Pt-Ni nanowire annealed in hydrogen at 250°C.

Figure 1
Nitrogen and Sulfur Dual-Doped Iron-Graphene Catalysts for Oxygen Reduction Reaction
Authors: Lin Yu-Chuan , Liu Chia-Chi , Huang Hsin-Chih , Wang Chen-Hao
Published: February 2020

This study investigates nitrogen and sulfur as the dual dopants in the iron-graphene catalysts (N-S-iron-graphene) for the oxygen reduction reaction (ORR). After the pyrolysis in the specific temperature, N-S-iron-graphene catalysts demonstrates an excellent ORR ability with the electron-transfer number of 3.99, which is very close to the ideal four electron-transfer number. From the structure analysis, the graphene-like structure is found in the outer surface of the catalysts, which improves the electrical conductivity. XPS spectra shows the high amounts of pyridinic-N, quaternary-N and thiophene-S of chemical structures in the catalysts, which can significantly enhance the ORR activity. In addition, the catalyst has an excellent stability after 30,000 cycles of stability test. It confirms that nitrogen and sulfur dual-doped iron-graphene catalysts can enhance the ORR ability due to the synergistic effect.
Tuning Pt-Skin or M-Rich Surface on Bimetallic Nanoparticles (Pt3Ni, PtBi, Pt3Co) for Enhanced Electrocatalytic Activities
Authors: Jiang Yan-Xia , Zhang Bin-Wei , Zhen Chun-Hua , Sun Shi-Gang
Published: February 2020

Controlling surface composition of bimetallic catalysts is of significance in energy conversion and storage. We synthesized a series of bimetallic catalysts of different surface composition on porous graphitic carbon (PtBi/PC, Pt3Ni/PC, Pt3Co/PC: figures A, C, E, G) with average diameter < 4 nm by controlled thermal treatment method.

Formic acid oxidation on Pt/C is performed via the poisoning path (figure B), whereas oxidation of formic acid to form CO2 is done via the non-poisoning path on the PtBi/PC (figure D). The value of the peak current density is 4.6 times of that of the Pt/C catalysts. Pt3Ni catalyst with Pt-skin surface showed over 300% increase in mass activity compared with Pt/C for the oxygen reduction reaction (figure F). When we tuned the surface composition to Ni-rich, it showed 300% increasein mass activity when compared with Pt/C towards oxidizing of HCOOH. Ethanol oxidation on Pt3Co/PC with Pt-skin surface showed 2.5 times on mass activity than that of Pt/C. In addition, we proposed a new method to characterize Pt-skin or M-rich structure by using formic acid oxidation as probe reaction with the characterization of cyclic voltammetry and electrochemical in situFTIRs.

Our approach to control surface composition can be used to design nanocatalysts for different reaction and enhance their catalytic performances. and The method is simple and clean that is effective and promotional to be industrialized.

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PdCu/C Catalysts for the Electrochemical Oxidation of Renewable Polyalcohols
Authors: Haan John , Muneeb Omar , Estrada Jose , Flores Jennifer , Nguyen Kelly
Published: February 2020

The development of the alkaline anion exchange membrane (AEM) for the direct liquid fuel cell opened up opportunities for the use of new fuels (that oxidized inefficiently in PEM fuel cells) and new catalysts (that corroded easily in PEM fuel cells).  The first fuel studied in depth was ethanol because it oxidizes much more efficiently in alkaline media than acidic media.  However, the same palladium catalyst that oxidizes ethanol in alkaline media can also be used to oxidize several other alcohol fuels including polyalcohols such as ethylene glycol (EG), propylene glycol (PG), and glycerol (G).  Therefore, we recently demonstrated a flexible fuel direct liquid fuel cell that operated on alcohols such as ethanol, EG, PG, and G. However, these fuels all oxidize more slowly then ethanol, requiring significant kinetic improvement to be used practically.

We tested various combinations of Pd:Cu and compared them in each polyalcohol fuel, EG, PG, and G.  We observed that any quantity of Cu added to the Pd produced an increase in oxidation rate compared with pure Pd for all three polyalcohol fuels.  We also observed a down-shift in d-band center as observed by XPS.  We hypothesize that the addition of Cu to the Pd results in a combination of the electronic and bifunctional effects.  The electronic effect is caused by perturbations in the electronic structure of Pd, the primary catalyst, induced by the Cu. The bifunctional effect is caused by the co-catalysis of Pd and Cu directly on the surface of the catalyst.
Electrochemical Approaches to Synthesis Different (di)Phenylphosphine Oxide Derivatives
Authors: Khrizanforova Vera , Khrizanforov Mikhail , Gryaznova Tatyana , Budnikova Yulia
Published: February 2020

Phosphine oxides are successfully used as building blocks, specifically, for the synthesis of substituted vitamin D3 analogs. Tertiary phosphine oxides are key targets in the chemistry of organophosphorus compounds. They are widely used as ligands for metal complex catalysts, special solvents for stabilization of nanosystems in the synthesis of semiconductors, extractants for noble, rare-earth, and transuranium elements, fire-retardants, and photochromic and lumines-cent materials.1-4

Of particular interest are functionalized tertiary phosphine oxides; however, their synthesis involves some difficulties. A convenient synthetic approach to such compounds is based on the addition of secondary phosphine oxides to functionally substituted alkynes at high temperature by using equivalent amounts of oxidant and catalyst.1-4

In our work the synthesis of different (di)phenilphosphine oxide derivatives in electrocatalytic conditions have been performed. Our approach provides an efficient way to construct different phosphorus-containing products, including bisphosphonates, benzo[b]phosphole oxides, alkynyl(diaryl)phosphine oxides with high yield at room temperature in oxidant-free media. The mechanism includes forming cobalt and silver complexes with diphenylphosphine oxide, their electrochemical reduction/oxidation leads to binding with acetylene and obtaining target products.

Acknowledgements

This work was supported by the Russian Science Foundation no. 14-23-00016.

References

1 Wang, T.; Chen,S.; Shao, A.; Gao, M.; Huang, Y.; Lei, A. Org.Lett. 2015, 17, 118.

2 Chen, Y.-R.; Duan, W.-L. J. Am. Chem. Soc. 2013, 135, 16754.

3 Dvorko, M. Yu.; Glotova, T. E.; Ushakov, I. A.; Gusarova, N. K. Russ. J. Org. Chem. 2010, 45, 485.

4 Srinivas, V.; Balaraman, E.; Sajna, K.V.; Kumara Swamy, K.C. Eur. J. Org.
Chem.

2011, 4222–4230.

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Activity Trends of Co3O4 on Metallic Interlayers Supported on Porous Carbon Support
Authors: Kishor Koshal , Saha Sulay , Pala Raj Ganesh , Sivakumar Sri
Published: February 2020

We explore the design of support for Co-based water oxidation electrocatalysts. While earth abundant metals (EAM) have adequate conductivity, they lack the porosity provided by carbon support. To alleviate this problem and make the electrode more three dimensional, we demonstrate the utility of electrodeposited metal interlayers that not only offers parallel electron conduction pathways, but also due to variation of exposed surface during electrodeposition and electronic structure which promotes electrocatalytic activity of Co3O4. To see the effect of parallel metal interlayer, a range of non-noble earth abundant metals are explored. Maximum OER activity is found to be with Cu-modified metal support which is attributed to its higher electrical conductivity with enhancement of OER activity about 6 times in similar condition with respect to unmodified porous carbon support. The OER activity of electrodeposited Co3O4 is found to have a linear relationship with electrical conductivity with electron donor metals and electron acceptor metals individually. The above understanding can be useful in increasing OER activity of the same electrocatalyst by tuning support-catalyst interaction.