bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Nb2O5/Graphene Supported Platinum-Cobalt Nanocomposite as Electrocatalyst for the Alkaline Alcohols Fuel Cells
Authors: Kepeniene Virginija , Vaiciuniene Jurate , Kondrotas Rokas , Pakstas Vidas , Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus 
Published: February 2020

In the present work, niobium oxide/graphene supported PtCo catalyst with the Pt:Co molar ratio 1:7 (denoted as PtCo(1:7)Nb2O5/GR) was fabricated by means of the rapid microwave heating polyol method. The surface morphology, structure and composition of the synthesized catalyst were examined by transmission electron microscopy, X-ray diffraction and inductively coupled plasma optical emission spectroscopy. The electrocatalytic activity of the synthesized catalyst towards the oxidation of alcohols – ethanol, methanol and ethylene glycol in an alkaline medium was investigated by means of cyclic voltammetry and chronoamperometry.
It has been determined that the Pt loadings was 0.285 mg Pt cm–2 in the synthesized PtCo(1:7)Nb2O5/GR catalyst. For comparison, the bare commercial Pt/C (Sigma-Aldrich) catalyst with 10% wt. Pt with the Pt loading of 0.385 mg Pt cm–2 was used. The electroactive surface areas (ESAs) of the prepared and commercial catalysts were determined from the cyclic voltammograms of PtCo(1:7)Nb2O5/GR and Pt/C catalysts recorded in a deaerated 0.5 M H2SO4 solution at a sweep rate of 50 mV s–1by calculating the charge associated with the hydrogen adsorption.
According to the data of TEM analysis, the Pt nanoparticles of ca. 1-2 nm in size were successively deposited onto the surface of graphene nanosheets.
It has been found that niobium oxide/graphene supported PtCo catalyst with the Pt:Co molar ratios 1:7 show an enhanced electrocatalytic activity towards the oxidation of alcohols in an alkaline medium as compared with that of 10% wt. Pt implicated commercial Pt/C catalyst. Alcohols oxidation current densities were found to be ca. 3 – 40 times higher at the PtCo(1:7)Nb2O5/GR catalyst in comparison with those at the commercial Pt/C catalyst. The prepared catalyst seem to be a promising anodic material for direct alcohols fuel cells.

Acknowledgement

Postdoctoral fellowship is being funded by European Union Structural Funds project ”Postdoctoral Fellowship Implementation in Lithuania”.
Enhancement of Electrocatalytic Activity for Oxygen Reduction Reaction on TiO2-Supported Pt-Based Intermetallic Compound Catalysts
Authors: Tanabe Toyokazu , Gunji Takao , Sasaki Kengo , Jeevagan Arockiam John , Tsuda Takashi , Kaneko Shingo , Saravanan Govindachetty , Abe Hideki , Tanaka Manabu , Matsumoto Futoshi 
Published: February 2020

Stable and long-term electrocatalytic performance towards cathodic oxygen reduction reaction (ORR) was achieved by impregnation of Pt-based nanoparticles (NPs) on anatase titania (TiO2) support. For example, organometallic precursors PtCODCl2 and C10H14CuO4 and TiO2 or carbon black (CB) supports were co-reduced using lithium triethylborohydride to achieve intermetallic phase between Pt and Cu on TiO2(or CB) under ambient temperature. Finely dispersed PtCu NPs with an average particle size of 3 nm were achieved through wet-chemical synthetic route.
Potential cycle with PtCu/CB in 0.1 M HClO4 aqueous solution between 0.4-1.1 V (vs. RHE) accelerates ORR (Fig. 1) because of the formation of dealloyed surface of PtCu NPs caused by dissolution of Cu from the surface of PtCu NPs. The dealloyed PtCu/CB showed the highest electrocatalytic activity both in terms of onset potential as well as cathodic current density compared to Pt/CB as well as PtPb/CB and PtNi/CB towards ORR (Fig. 2). The onset potential of PtCu/TiO2 is shifted to higher electric potential by 180 mV compared to Pt/CB (Fig. 3).
Gold-Zinc-Cobalt Deposited on Titanium as Electrocatalysts for Borohydride Oxidation
Authors: Balčiūnaitė Aldona , Lichuina Svetlana , imkūnaitė Dijana , Zabielaitė Ausrine , Selskis Algirdas , Tamaauskaitė-Tamaiūnaitė Loreta , Norkus Eugenijus 
Published: February 2020

Investigation of the electrochemical oxidation of borohydride in alkaline solutions on the ZnCo alloy deposited on the titanium surface and modified with gold nanoparticles (denoted as AuZnCo/Ti) is presented. The ZnCo alloy coatings with the thickness of ~5 µm were deposited on the titanium surface (1 x1 cm) via electrodeposition from the electrolyte described in Ref. [1]. Au crystallites were deposited on the ZnCo/Ti surface via the galvanic displacement technique. The ZnCo/Ti catalysts were immersed into the 1 mM HAuCl4 + 0.1 M HCl solution at 25 oC for 0.5, 1 and 5 min, respectively [2].
The morphology, structure and composition of the prepared catalysts were examined by Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Analysis and Inductively Coupled Plasma Optical Emission Spectroscopy. Electrocatalytic activity of the prepared catalysts was investigated towards the oxidation of borohydride by means of cyclic voltammetry, chronoamperometry and chronopotentiometry.
It has been determined that the AuZnCo/Ti catalysts with Au loadings of 31, 63 and 306 µg cm-2 show enhanced catalytic activity towards electro-oxidation of BH4
– ions as compared to that of ZnCo/Ti or Co/Ti catalysts. The chronoamperometry and chronopotentiometry studies also confirmed a high electrocatalytic activity of the AuZnCo/Ti catalysts for the direct electro-oxidation of BH4
– ions as compared to that of ZnCo/Ti and Co/Ti catalysts.

References

[1] E. Juzeliunas, S. Lichusina. Patent of the Republic of Lithuania No. 5481 26.03.2008.
[2] L. Tamasauskaite-Tamasiunaite, A. Jagminiene, A. Balciunaite, A. Zabielaite, J. Vaiciuniene, A. Selskis, R. Juskenas, E. Norkus. Int. J. Hydrogen Energy 38 (2013) 14232-14241.
Laser Sealing Technique for Fuel Cell Application
Authors: Lin Chih-Chia , Wang Wen-Lin , Shie Ho-yan 
Published: February 2020

A complete fuel cell stack comprises several single cells with end plates, collector plates, monopolar plates, gasket, and MEA components. Electron generated from cells can be conducted through bipolar plates. However, the amount of cell components increases with great cell power, which is inconvenient for fuel cell assembly process and mass production. During 2010, fuel cell systems were manufactured more than 15,000, the power of which was more than 8MW. With the market growth of hydrogen energy and fuel cells, developing high-speed modular assembly technique becomes a priority research to meet market requirements. Furthermore, extra back pressure is necessary for fuel gas in the fuel cell stack utilized in transportations to promote the fuel cell performance; gas leakage therefore becomes an important issue with an increase in the amount of cell components and gas pressure.
Consequently, laser welding technique is utilized in fuel cell stack design, which has advantages of narrow welding path and high welding aspect ratio, small amount of deformation for specimens, fast welding velocity, high strength welding, and easily integrated into automation equipment, to achieve the objective for high strength and accuracy modular sealing and promoting production capacity and quality. Parameter analysis for laser welding, optical measurement tests and peel tests are conducted to obtain the optimal welding quality and strength, the sealing strength of which can sustain at least 0.4 MPa stress (4 atm pressure). Moreover, new fuel cell stack structure is subsequently designed for this high strength and accuracy modular sealing technique in the future research.
Invited: Engineering Net Water Balance in Polymer Electrolyte Fuel Cells
Authors: LaManna Jacob M , Mench Matthew M. 
Published: February 2020

The motivation of this work is to understand and control the water balance of a polymer electrolyte fuel cell to reduce anode water buildup and degradation. A custom 4.8 cm2 fuel cell with precision liquid coolant control was used to acquire the water balance data. The precision liquid coolant ensures stable, high accuracy thermal boundary conditions for the analysis. The net water drag coefficient was measured by placing high accuracy dew point temperature sensors at the inlets and outlets of the fuel cell to measure water balance. Gradients in pressure, inlet relative humidity, and temperature were used to isolate hydraulic, diffusion, and temperature driven flow through the membrane and porous media.
This presentation will focus on the effects of anode land width, channel shape, and diffusion media tortuosity on net water drag. Using neutron radiography data that has been previously presented (1, 2) coupled with net water drag data, conclusions will be presented relating performance and water transport and storage. Data from this work will build upon an online database of benchmark data for the modeling community made available through this Department of Energy EERE supported program.

Acknowledgements

This work is funded by the United States Department of Energy Efficiency and Renewable Energy (EREE) Program through General Motors under Award Number DE-EE0000470.
1. J. M. LaManna, S. Chakraborty, J. J. Gagliardo and M. M. Mench, International Journal of Hydrogen Energy, 39, 3387 (2014).
2. J. LaManna and M. Mench, Meeting Abstracts, MA2014-01, 646 (2014).
The Role of Gas Diffusion Layer in Cationic Contamination and Mitigation in Polymer Electrolyte Fuel Cells
Authors: Uddin Md. Aman , Park Jaehyung , Wang Xiaofeng , Qi Jing , Pasaogullari Ugur , Bonville Leonard J. , Molter Trent 
Published: February 2020

Cationic impurities may get introduced into Polymer Electrolyte Fuel Cells (PEFC) from the ambient air (e.g. roadside contaminants) and from the corrosion of stack and balance of plant components. Recovery from cationic impurities is investigated by simulating the cationic contamination with equilibrium uptake of the membrane electrode assembly (MEA) in a salt solution. The cation uptake into the ionomer was performed by soaking the MEA in 0.9 mM CaSO4 and 29.1 mM H2SO4 solution following Kienitz’s procedure (1). Three different methods were used to soak the MEA into the solution to understand the role of the gas diffusion layers (GDL) (as shown in Figure 1): (A) entire CCM is exposed (50 cm2), (B) portion of the CCM is covered with GDL and the remainder is exposed, and (C) portion of the CCM is covered with GDL and the remainder is covered with PTFE seals used in cell assembly. Prior to soaking, all MEAs were tested to obtain baseline performance. In the first two methods (A and B), significant performance drop were observed due to Ca2+ presence inside the CCM (shown in Figure 2). In case of the third method (C), there were no significant performance changes. Even when the soaking time was increased to more than 4 times in method C compared to method A, cell performance did not change significantly. It is clear that GDL acts as a barrier to the transport of Ca2+ to the CCM. When surfactant was added to the cationic solution to increase the wettability of the GDL, a drop in the performance was observed.
To recover the cell performance, we re-protonated the CCMs in an acidic solution similar to Qi et al. (2). They re-protonated CCMs contaminated at different levels of Al3+ (similar to method A in Figure 1) with ex-situ soak in the acid solution (1 M H2SO4) and recovered the full performance decay. We also recovered the performance back near to the baseline when only the CCM is soaked (method A), but for the other two methods, the cell performance is partially recovered. We also performed in-situ injection of 1-10 mM H2SO4, and the cells were seemingly not affected by the in-situ injection of the acid solution. We conclude that the GDL is hindering the transport of Ca2+ in and as well as out of the MEA. Thus, recovery appears to be possible but additional factors need to be identified that hinder this process.

Acknowledgements

The authors are grateful for the financial support of the Department of Energy (DOE)-EERE, DE-EE00000467 (University of Hawaii, prime contractor, Jean St-Pierre, PI).

References

B. Kienitz, B. Pivovar, T. Zawodzinski and F. H. Garzon, J. Electrochem. Soc., 158, 9 (2011).

J. Qi, X. Wang, U. Pasaogullari, L. Bonville and T. Molter, J. Electrochem. Soc., 160, 9 (2013).
Ångstrom Resolved Monitoring of Noble Metal Oxide Growth in Nano-Confined Spaces
Authors: Shrestha Buddha Ratna , Baimpos Theodoros , Raman Sangeetha , Valtiner Markus 
Published: February 2020

Structure and dynamics at electrochemical solid/liquid interfaces of metal electrodes drive functionality, stability and capabilities in a wide range of important technologies such as batteries, super capacitors, or fuel cells. In particular, with the downsizing of the electrochemical devices, electrochemistry in confined spaces (nanospaces) has become a major focus of current research efforts. We use a newly developed and unique electrochemical surface force apparatus1 in order to unravel electrochemical processes undergoing at well-defined nano-confined electrodes. We can monitor metal-oxide film formation with Å-accuracy during potentiostatic and potentiodynamic polarizations, within nano-confined spaces (less than 10 nm up to 100’s of nm). We report unexpectedly strong electrochemical depletion forces acting between apposing surfaces during active electrochemical processes such as potential pulse application or reduction of oxide. Such forces and the associated electric-field gradients might have significant effect in coarsening or mechanical dissolution of nano-confined spaces and confined particles. In addition, we are also able to reveal a real time in-situ monitoring of electrochemical interfaces with Angstrom resolution. We have, for the first time, monitored oxide growth on noble metals in sulfuric acid solutions in real time, with Ångstrom resolution in thickness and milliseconds resolution in time. Our experiments reveal stark differences of oxide thickness and electronic properties during potentio-dynamic and potentio-static oxide growth on noble metals, which will be discussed in the presentation.
1. Valtiner, M.; Banquy, X.; Kristiansen, K.; Greene, G. W.; Israelachvili, J. N., The Electrochemical Surface Forces Apparatus: The Effect of Surface Roughness, Electrostatic Surface Potentials, and Anodic Oxide Growth on Interaction Forces, and Friction between Dissimilar Surfaces in Aqueous Solutions. Langmuir
2012,
28 (36), 13080-13093.
Synthesis and Characterization of Controllably Branched Anodized Aluminum Oxide Pores
Authors: Gillette Eleanor , Wittenberg Stefanie Sherrill , Banerjee Parag , Lee Sang Bok 
Published: February 2020

Well-ordered anodized aluminum oxide (AAO) is a widely known porous material which has been used in a variety of applications. One of the advantages of AAO is its tunable pore diameter and length, which are controlled by the anodizing conditions. Additionally, more complex structures can be produced by modifying the anodization and etching conditions. Here we present a technique for introducing branch points into the pores which allows for controllable branching in sections of the pores while maintaining straight, hexagonally arrayed, regular structures throughout the rest of the alumina membrane.
We also demonstrate that this method can be integrated with a strategy for barrier layer thinning and removal which allows for the use of the underlying aluminum as a current collector. This allows these 3-D networks to be used as electrodes, without having to withstand the normal processing route, which requires wet etches to remove the aluminum and then remove the barrier layer, followed by vacuum deposition of a new current collector. This process is difficult to carry out for very thin membranes, since AAO is brittle and prone to cracking and shattering. This new combination of techniques allows the production and electrochemical characterization of very thin (>3um) porous networks, ranging from well-ordered 1D channels to highly branched 3D networks.
First, we demonstrate electrodeposition into these pores, to confirm the opening of the barrier layer, and to demonstrate that the branched pores are accessible to electrolyte. Then, a variety of networks of different thicknesses and numbers of branch points are characterized by electrochemical impedance spectroscopy. Since this method allows branch points to be added at various intervals along the pores, networks with different numbers of branch points as well as with different spacing between the branch points can be analyzed as well. This study is focused on understanding the movement of electroactive species through porous networks of increasing complexity, as well as demonstrating a new potential template for electrodeposition of 3D electrodes.
Electron Transfer Kinetics at Co Porpyrin-Modified Electrodes with Controlled Interfaces
Authors: Ikeda Katsuyoshi , Sato Shino 
Published: February 2020

Electrocatalysis has been extensively studied in the fields of both fundamental research and applications such as fuel cells. Chemical modification of an electrode surface is quite beneficial to non-catalytic metals to introduce catalytic activity for a particular electrochemical reaction. For example, metalloporphyrin-modified electrodes are known to act as electrocatalysts for oxygen reduction reaction (ORR). Chemical design of molecular catalysts is clearly one of key issues to realize highly efficient electrocatalysts. However, the electron transfer rate at such a chemically modified electrode is significantly affected by electronic coupling between the metal and molecular catalysts. In this work, a gold electrode surface was self-assembly modified with Cobalt porphyrin (CoTPP) having ORR activity. To control the connection between Au and CoTPPs, bridge monolayers were formed on the electrode using various thiol- or isocyanide-molecules, and CoTPPs were then immobilized on top of the bridge layers. For isocyanide-monolayers, the electrode-molecule junctions were also controlled by forming Pd- or Pt-atomic layers on the Au surface. The electron transfer rate for ORR was thoroughly investigated for such various CoTPP-modified electrodes using the rotating disk electrode (RDE) method.
The junction between the electrode and the molecular monolayers was controlled as shown in Fig. (a). The Pd monoatomic layer on an Au surface (Au/PdML) was prepared by the underpotential deposition (UPD) method. The Au and Au/PdML electrodes were self-assembly covered with TPDI (4,4’-terphenyl diisocyanide) molecules. As shown in Fig. (b), the adsorption geometry of TPDIs, measured by PM-IRRAS, was on-top configuration on Au and bridge on Au/PdML. The 2120 cm-1 peak found on both electrodes was attributed to be the unbound NC streching mode. Figure (c) shows Tafel plots for ORR on the TPDI-CoTPP monolayer formed on each electrode. Electron transfer rate on the Au/PdML was much faster than that on the Au. The elementary step of the electron transfer between O2molecule and CoTPP is not affected much by the presence of the Pd monolayer, as the Tafel slop is nearly identical for both plots. Therefore, this result indicates that the electron transfer rate at the electrode-molecule interface was significantly enhanced by controlling the adsorption geometry, leading to the enhancement of the ORR activity of the electrode.
Figure (a) Schematic illustration of TPDI-CoTPP monolayers on metal electrodes. (b) PM-IRRAS spectra of TPDI-SAMs on Au and Au/PdML electrodes. (c) Tafel plots for the ORR on TPDI-CoTPP monolayer formed on Au and Au/PdML electrodes.
Modifying Oxide Single Crystal Surfaces to Study Photoinduced Electron Transfer
Authors: Parkinson Bruce A 
Published: February 2020

Single crystal oxide semiconductor electrodes provide an ideal experimental system for the elucidation of the models and parameters that control light absorption, charge separation, and transport at semiconductor/liquid interfaces. Such fundamental investigations can prove very valuable in the understanding of dye sensitized nanocrystalline solar cells. The single crystal experimental system is much less complex than its nanocrystalline counterpart and the study of well-defined crystallographic surfaces allows for more definitive conclusions to be made concerning the relation between sensitizer attachment and surface structure and the sensitizer’s performance. I will report recent work on the sensitization of low index faces of both anatase and rutile forms of TiO2 and ZnO single crystals with dyes, quantum dots and polymers. We employ atomic force microscopy (AFM) to verify that atomically flat terraced oxide surfaces are prepared and to elucidate the structure of the sensitizers adsorbed on these surfaces. Photocurrent spectroscopy and attenuated reflection spectroscopy are used to correlate the photocurrent response with the optical absorption of the sensitizing species and the relative electron injection efficiencies of for instance dye monomers and aggregates. We have also recently begun to grow homoepitaxial layers on both anatase and rutile using atomic layer deposition (ALD). These layers can have superior electronic properties compared to the substrate crystal and allows us to control the doping density in the near surface region. The primary focus of this talk will be on CdSe and PbS quantum dots as sensitizers. PbS quantum dots adsorbed on anatase (001) surfaces irradiated with light of >2.5 times their band gap have been shown to produce more than one injected electron per incident photon (1), a process known as carrier multiplication or multiple exciton generation (MEG). Harnessing MEG may result in more efficient solar conversion devices.
1. Justin B. Sambur, Thomas Novet and B. A. Parkinson, “Multiple Exciton Collection in a Sensitized Photovoltaic System”, Science, 330, 63-66, (2010)