bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charge Transfer Kinetics in LiFePO4 Porous Electrodes: Butler-Volmer Equation Vs Marcus Theory
Authors: Bai Peng , Bazant Martin Z. 
Published: February 2020

The local rates of charge transfer in carbon-coated LiFePO4 porous electrodes are extracted from chronoamperometry experiments by a simple statistical theory,1 which yield curved Tafel plots that cannot be explained by the standard Butler-Volmer (BV) model for lithium intercalation. The microscopic Marcus-Hush-Chidsey (MHC) model,2 however, accurately captures the deviation from the Tafel slope (α=0.5) at overpotentials larger than 150mV. The fitted reorganization energy is in excellent agreement with the Born solvation energy for electron transfer between the carbon coating and the Fe2+/Fe3+ redox site estimated from first principles dielectric properties, which implies that the kinetics are limited by electron transfer at the solid (carbon) – solid (LixFePO4) interface, rather than by lithium ion transfer at the liquid (electrolyte) – solid interface, as previously assumed. This discovery suggests the need for a paradigm shift in mathematical modeling of electrochemical systems, replacing the BV equation with quantum mechanical theories of electron transfer3 and incorporating statistical effects of non-equilibrium thermodynamics.4 The proposed method of chronoamperometry and Tafel analysis generalizes Chidsey’s method for homogeneous monolayers and allows fundamental rate constants to be determined for phase-transforming particles and porous electrodes.

References

1. Bai, P., Tian, G.Y. Statistical kinetics of phase-transforming nanoparticles in LiFePO4 porous electrodes. Electrochim. Acta
89, 644-651 (2013).
2. Chidsey, C.E.D. Free-Energy and Temperature-Dependence of Electron-Transfer at the Metal-Electrolyte Interface. Science
251, 919-922 (1991).
3. Marcus, R.A. Electron-Transfer Reactions in Chemistry - Theory and Experiment. Reviews of Modern Physics
65, 599-610 (1993).
4. Bazant, M.Z. Theory of Chemical Kinetics and Charge Transfer based on Nonequilibrium Thermodynamics. Acc. Chem. Res.
46, 1144-1160 (2013).

Figure

Tafel plot of the reaction rates extracted from chronoamperometry experiments, which deviate from the Butler-Volmer (BV) model, but can be captured by the Marcus-Hush Chidsey (MHC) model. Overpotentials are scaled to the thermal voltage kBT/e≈25.7mV.
Modular Electrolyte Additives: Decoupling Uniform Deposition and Stability
Authors: Cheng Gang , Kaye Steven S. , Li Bin 
Published: February 2020

The stability and cycle life of lithium-ion batteries are limited by unfavorable reaction between the electrodes and electrolyte. To reduce this problem, electrolyte additives are used to passivate the cathode and/or anode with a protective coating. To function effectively, such additives must both deposit uniformly on the electrode surface and form an electrochemically inert coating. These dual constraints severly limit the set of viable additives.
Wildcat Discovery Technologies has developed a new, modular additive concept in which additives are bound to a molecular core that enables uniform deposition on the electrode surface. Attachment of conventional additives to the core molecules provides improved SEI stability, increasing coulombic efficiency, cycle life, and thermal stability. Furthermore, by decoupling the requirements for uniform coating and chemical stability, new classes of additives can be used. In this talk, I will discuss the development of these modular additives as well as their performance with a both commercial and future cell chemistries.
Zinc-Cobalt Alloy Deposited on the Titanium Surface As Electrocatalysts for Borohydride Oxidation
Authors: Tamasauskaite-Tamasiunaite Loreta , Lichusina Svetlana , Balciunaite Aldona , Zabielaite Ausrine , Simkunaite Dijana , Vaiciuniene Jurate , Selskis Algirdas , Norkus Eugenijus 
Published: February 2020

The present work is focused on the investigation of the electrochemical oxidation of borohydride in alkaline solution on low-cost ZnCo alloy deposited on the titanium surface (denoted as ZnCo/Ti). 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]. Prior to ZnCo alloy deposition, the titanium plates were degreased with acetone and then pretreated in diluted H2SO4 (1:1 vol) at 90 oC for 10 s. Cobalt coatings with the thickness of ~3 µm were deposited from the same electrolyte [1] with only difference that zinc ions were excluded from the plating bath.
The morphology, structure and composition of the prepared catalysts were examined by FESEM, EDS and ICP-OES. Activity of the fabricated catalysts was investigated towards the oxidation of borohydride by means of cyclic voltammetry and chronoamperometry.
It was found that the ZnCo alloy coating, electrodeposited on the titanium surface, consists of ~81.3 at. % of Zn and ~16.1 at. % of Co.
It has been determined that the Co/Ti and ZnCo/Ti catalysts catalyzes oxidation of H2 generated by catalytic hydrolysis of BH4
– and direct BH4
– ions oxidation. Notably, the H2 oxidation current densities measured on both catalysts are similar and reach up to 60 mA cm–2, whereas, the borohydride oxidation current densities are ~3-6 times higher on the ZnCo/Ti catalysts than those obtained on the Co/Ti catalyst. The chronoamperometry and chronopotentiometry studies also confirmed a high electrocatalytic activity of the ZnCo/Ti catalyst for the direct electro-oxidation of BH4
– ions as compared to that of Co/Ti electrode.
The ZnCo/Ti catalysts are promising low-cost anode material for direct borohydride fuel cells.

References

[1] E. Juzeliûnas, S. Lichušina. Patent of the Republic of Lithuania No. 5481 26.03.2008.
Density Functional Theory Studies of Formic Acid Oxidation on Pd (111), (100) and (110) Facet
Authors: Huang Shanqisong , Hu Chenyao 
Published: February 2020

In the last fifty years, great interest and investment have been devoted to direct formic acid fuel cells (DFAFC) for its high-energy conversion efficiency, low operating temperature, low pollutant emission, ease of handling and processing of the liquid fuels, and integrated well with the existing energy infrastructure[1-3]. The electro-oxidation of formic acid in DFAFC is currently being investigated by many research groups.
Pd is the one of the most promising anode catalysts used in DFAFC due to its higher formic acid oxidation activity and excellent CO tolerance[4]. However, the study of structure sensitivity of formic acid oxidation on Pd (111), (100) and (110) facet is rare. So weather the dsorption behaviors and oxidation mechanisms of formic acid on different Pd facets are the same.
In the present study, we calculated the adsorption and decompostion of formic acid on the Pd (111), (100) and (110) Facet. The results show that Pd (100) is the best facet for the dissociation of formic acid, which means the (100) facet exhibit the highest activity toward the formic acid electrooxidation.
Reference
[1] Chen, X. et al., J. Am. Chem. Soc., 133(11), 3693 (2011).
[2] Maiyalagan, T. et al., J. Power Sources, 211, 147 (2012)
[3] Mazumder, V. et al., Nano Lett., 12(2), 1102 (2012)
[4] Yang, J. et al., J. of Mater. Chem., 21(10), 3384 (2011)
Local Proton Conductance in the Proton Exchange Membranes: A Density Functional Study
Authors: Singh Raman Kumar , Tsuneda Takao , Miyatake Kenji , Watanabe Masahiro 
Published: February 2020

The performance of the proton exchange membrane fuel cells (PEMFCs) is closely related to the performance of the proton exchange membranes and many researchers have focused on the development of new proton-conducting polymer membranes as an alternative to Nafion (DuPont) membranes. Recently, the multiblock sulfonated poly (arylene ether sulfone)s (SPE) containing highly sulfonated hydrophilic component seem to be very promising candidates and have shown many advantages over Nafion. However, their proton conductivities are still lower than Nafion at low relative humidity conditions.1 To make clear why perfluorinated polymer membrane Nafion is superior to other membranes in the proton conductivity at low humidity, we firstly compared their hydrated structures. It was found that minimum three water molecules are needed to detach a proton from the sulfonic acid group in both membranes and the SPE membrane has two types of the sulfonic acid groups: active “separated” and inactive “paired” groups for proton conductance. To explore the possibility of the proton conductance in the vehicle mechanism at low humidity, we examined the relay model (Fig. 1) of protonated water clusters between the sulfonic acid groups in Nafion and found that it needs 33 kcal mol-1, which is common in usual reactions. This seems to indicate that relay model may contribute to the high proton conductivity of Nafion at low humidity.2

[1] K. Miyatake, B. Bae and M. Watanabe, Polym. Chem., 2011, 2, 1919.
[2] R. K. Singh, T. Tsuneda, K. Miyatake and M. Watanabe 2013 (Submitted)
Effect of Sintering Atmosphere and Particle Size on the Ionic Conductivity of Gadolinia-Doped Ceria
Authors: Batista Rafael Morgado , Muccillo Eliana Navarro Santos 
Published: February 2020

Gadolinia-doped ceria has been intensively investigated over the last decades as a promising electrolyte and electrode material for intermediate-temperature solid oxide fuel cells [1]. The sintering behavior of this solid electrolyte in reducing atmosphere is different from that in air, because of the reduction of Ce4+ to Ce3+[2]. In this case, changes in the microstructure and in the related properties are expected to occur, due to variation in the oxygen-vacancy concentration.
In this work, the effects of the sintering atmosphere and the particle size of powders on densification and ionic conductivity of Ce0.9Gd0.1O2-δ were systematically investigated.
Ce0.9Gd0.1O2-δ commercial powders (>99.5%, Fuel Cell Materials) with specific surface area ranging from 7.4 to 210 m2.g-1were used as starting materials. Cylindrical pellets were prepared by uniaxial and isopressing following by sintering at 1250°C for 2 h under different atmospheres.
The average initial particle size of the powders was evaluated by nitrogen adsorption (Quantachrome, NOVA 1200) using the BET method. Characterization of the sintered materials was carried out by density measurements, thermodilatometry (Anter-1161, Unitherm), electronic Raman spectroscopy (InVia Raman microscope, Renishaw), electron paramagnetic resonance (Bruker-EMS), field-emission scanning electron microscopy (FEI, Inspect F50) and impedance spectroscopy (HP4192A). The mean grain size was estimated by the linear intercept method.
The sintered pellets reached relatively high densities (93 to 97% of the theoretical value) independent on the sintering atmosphere. The particle size determined by nitrogen adsorption of the starting powders was: 112, 23 and 4 nm for powders, hereafter named S1, S2 and S3, respectively. The linear shrinkage curves show that good densification of gadolinia-doped ceria is attained depending on the initial size of the powder particles. However, for isothermal treatments the densification is homogenized and all sintered pellets reached high values after 1250°C for 2 h.
All investigated properties changed to some extent with the sintering atmosphere and the initial particle size of the starting powders. The grain conductivity, for example, of Ce0.9Gd0.1O2-δ pellets sintered in air and under inert atmospheres (argon and nitrogen) exhibit the same bulk conductivity not depending on the sintering atmosphere, in spite of the changes observed in the electron paramagnetic signal.
References
[1] H. Yahiro, Y. Eguchi, K. Eguchi, H. Arai, J. Appl. Electrochem. 18 (1988) 527.
[2] Z. He, H. Yuan, J. A. Glasscock, C. Chatzichristodoulou, J. W. Phair, A. Kaiser, S. Ramousse, Acta Mater. 58 (2010) 1866.
Effect of Doping and Preparation Methods in Solid Electrolyte for Lithium Batteries
Authors: Beck Faith , Dontigny Martin , Zaghib Karim , Wang Donghai , Paranthaman Mariappan P , Goodenough John B. , Manivannan A. 
Published: February 2020

Recently, solid electrolytes with reasonable room temperature lithium ionic conductivity are being examined for high energy density batteries with safe operation. Several solid state electrolytes based on sulfides and oxides have been investigated [1]. Among them, Garnet phase materials have shown significant improvement in conductivity [2]. Garnet has cubic and tetragonal phases of which the cubic is high temperature with a high ionic conductivity value of 10-4 S/cm [3]. Several doped compositions have also been reported in order to improve the cubic phase ionic conductivity [4]. LLTO Perovskite system has also been reported for high ionic conductivity value of 10-4 S/cm [5,6]. Currently, we have synthesized a Ti, Cr, Ta doped Li7La3Zr2O12and LLTO by a simple Pechini process to investigate their ionic conductivities.
A Pechini method was used to synthesize these compoundsusing nitrate salts, ethylene glycol and citric acid in a 38:36:26 ratio respectively in de-ionized water. The samples were dried in an oven overnight at 120°C and then heat-treated at different temperatures to achieve the desired phases. The optimized product was heat treated at 1000°C for six hours, pelletized and then sintered again at higher temperatures (1200°C) to perform the ionic conductivity measurements using impedance spectroscopy.
Samples were characterized by XRD for phase analysis and electrochemical impedance performance has been investigated under varying temperatures and voltages. The effect of doping on the phase transition in LLZO and LLTO will be presented. Figure 1 shows the impedance plot for the Ta doped garnet (Li7La3Zr1.5Ta.0.5O12) at room temperature. Ionic conductivity value of 1.27(x10-4) S/cm has been obtained.
Detailed impedance measurements on systematic doping of Ti, Cr, Ta etc. in LLZO and LLTO phases using various sample preparation conditions, various ohmic contacts for the pellets will be discussed.
Figure. 1 Impedance plot for Li7La3Zr1.5Ta0.5O12
at room temperature.

Acknowledgements

This work has been supported by the US Dept. of Energy/NETL, EERE program. FRB acknowledges Oak Ridge Institute for Science and Education (ORISE) fellowship.

References

[1] J.W. Fergus, Journal of Power Sources, 195 (2010) 4554-4569.
[2] E. Rangasamy, J. Wolfenstine, J. Sakamoto, Solid State Ionics 206 (2012) 28-32.
[3] I. Kokal, M. Somer, P.H.L. Notten, H.T. Hintzen, Solid State Ionics 185 (2011) 42-46.
[4] Y. Jin, P.J. McGinn, Journal of Power Sources 196 (2011) 8683-8687.
[5] B. Antoniassi, A. H. M Gonzalez, S. L. Fernades, C. F. O. Graeff, Materials Chemistry and Physics 2011, 127, 51.
[6] O. Bohnke, Q.N. Pham, A. Boulant, J. Emery, T. Salkus, M. Barre, Solid State Ionics 2011, 188, 144.
Photocatalytic Hydrogen Production from Noble Metal Free Systems
Authors: Coutsolelos Athanassios Georgios , Charalambidis Georgios , Weinstein Julia A. , Guldi Dirk M. , Lazarides Theodore , Delor Milan , Sazanovich Igor , Georgakaki Irene , Peuntinger Katrin , Daphnomili Dimitra , Landrou Georgios , Kahnt Axel , Gryko Daniel , Sabatini Randy , McCamant David 
Published: February 2020

Abstract
With the global energy demand constantly rising, the need for developing new abundant and environmentally benign sources of energy is ever increasing.1 Consequently, solar energy is expected to play an increasingly important role in the future. One of the major strategies for solar energy conversion that is currently under development is the light-driven splitting of water into its constituent elements. Inspired by nature’s extensive use of metalloporphyrins as solar energy harvesters and electron transfer agents, artificial porphyrins have found prominent use as photosensitizers in hydrogen producing schemes.2The photocatalytic production of hydrogen can be accomplished by systems containing a photosensitizer, an electron relay, a sacrificial electron donor and a catalyst. The great challenges that remain in the field include the development of systems, which employ earth-abundant materials, and the improvement of the systems activity and durability.
Here, we report two noble metal free bioinspired photocatalytic systems, which use porphyrins or a corrole as photosensitizers and the cobaloxime as a catalyst (Figure 1). In the first one a water soluble Zn porphyrin was used as the photosensitizer and [CoIII(dmgH)2(py)Cl)] as the catalyst (Figure 1 left part). This system is effective in photoinduced H2 production in MeCN/water 1:1 with TEOA as a sacrificial donor.3 In the second one the photosensitizer is directly coordinated to the cobaloxime catalyst (Figure 1 right part). From transient absorption studies we observed an electron transfer from the chromophore to the cobalt catalyst, whereas the photocatalytic H2 production was low.4

REFERENCES
T. S. Teets, D. G. Nocera, Chem. Commun. 2011, 47, 9268.
J. R. Darwent, P. Douglas, A. Harriman, G. Porter, M. C. Richoux, Coord. Chem. Rev. 1982, 44, 83.
T. Lazarides, M. Delor, I. V. Sazanovich, T. M. McCormick, I. Georgakaki, G. Charalambidis, J. A. Weinstein, A. G. Coutsolelos, Chem. Commun. accepted, DOI: 10.1039/C3CC45025B.
K. Peuntinger, T. Lazarides, D. Dafnomili, G. Charalambidis, G. Landrou, A. Kahnt, R. P. Sabatini, D. W. McCamant, D. T. Gryko, A. G. Coutsolelos, D. M. Guldi, J. Phys. Chem. C, 2013, 117, 1647.
Thermal Activiation of Sr3Fe2O7-δ Electrocatalysts for Water Oxidation at Neutral pH
Authors: Takashima Toshihiro , Ishikawa Koki , Irie Hiroshi 
Published: February 2020

One of the great challenges in artificial photosynthesis is the development of efficient catalysts for oxidation of water to molecular oxygen. To date, the most extensively investigated catalysts for O2 evolution are nanostructured IrO2 and RuO2.1 They are robust and efficient water oxidation catalysts that exhibit high turnover frequencies under mild conditions. However, the high cost and scarcity of noble metals severely limit the widespread use of these catalysts for solar fuel production. Thus, considerable effort has been devoted for development of efficient catalysts based on more abundant materials. Recently, we demonstrated that stabilization of the Mn3+ species relative to charge disproportionation (2Mn3+ → Mn2+ + Mn4+) is an effective strategy to lower the overpotential under neutral pH.2,3 In this study, we examined O2 evolution activity of Sr3Fe2O7-δ
at various temperature conditions, as Sr3Fe2O7-δ
is known to show the charge disproportionation (2Fe4+ → Fe3+ + Fe5+) below 70 oC.4

A Sr3Fe2O7-δ
film electrode was prepared by a spray drying method. Sr3Fe2O7-δ
polycrystalline was synthesized by solid state reaction of SrCO3 and Fe2O3 and then suspended in ethanol. The suspension was deposited on a fluorine-doped tin oxide (FTO) electrode held on a 170 oC hotplate. The concentration of dissolved oxygen was monitored simultaneously with current density versus potential measurements using a needle-type oxygen microsensor.
Figure 1 shows polarization curves of a Sr3Fe2O7-
δ electrode at 30 oC and 70 oC. Upon sweeping the electrode potential at 30 oC, an increase in both anodic current and dissolved O2 concentration was observed at an onset potential of approximately 1.1 V. This result indicates that the observed anodic current was attributed to water oxidation. It should be noted that when the solution temperature was raised to 70 oC, the onset potentials for O2 production showed a negative shift from 1.1 V to 0.9 V. In this presentation, we will discuss the origin of the observed difference in O2 evolution activity at between 30 oC and 70 oC as well as temperature dependent efficiency of charge disproportionation of Fe4+.
References
1. Y. Zhao, E. A. Hernandez-Pagan, N. M. Vargas-Barbosa, J. L. Dysart, and T. E. Mallouk, J. Phys. Chem. Lett., 2, 402 (2011).
2. T. Takashima, K. Hashimoto, and R. Nakamura, J. Am. Chem. Soc., 134, 18153 (2012).
3. T. Takashima, K. Hashimoto, and R. Nakamura, J. Am. Chem. Soc., 134, 1519 (2012).
4. K. Kuzushita, S. Morimoto, S. Nasu, and S. Nakamura, J. Phys. Soc. Jpn., 69, 2767 (2000).
Improved Solar Energy Extraction Using a Combined Photo-Electrochemical / Thermal System for Domestic Applications
Authors: Ronaszegi Krisztian , Fraga Eric S. , Brett Dan J. L. 
Published: February 2020

Hydrogen generation is a significant area of energy research, with the aim to deliver low-cost, renewable energy sources which are environmentally friendly. One possible method is solar water splitting via photo-electrochemical reaction. Photo-electrochemical (PEC) hydrogen generation is a promising technology and alternative to photovoltaic (PV)-electrolyser combined systems. Although the PEC technology is promising, the efficiency of this technology is limited by thermodynamics and technical issues. Recent research has focused on aspects of materials development to improve efficiency. With multiple band-gap electrodes, the thermodynamic efficiency, and so the overall generated hydrogen quantity, can be increased. In the case of applications where there is a heating requirement beyond the need to generate hydrogen, there are further options for extracting energy from the solar resource by utilizing the longer wavelength radiation.
Just as it is possible to have a PV/T hybrid system, the PEC unit may also be used in a PEC/T hybrid mode, thus delivering both heat and power as a CHP system. Despite the promise of PEC technology, there is little research on it in terms of modelling and system simulation. According to the knowledge of the authors there is no published research on such hybrid systems.
In this work, a model of a hybrid PEC/T system has been implemented. Simulations with this model were carried out to compare PEC technology and its developments in terms of energy gain in a home environment where both heat and electricity demands are used. When there is heat demand, a buffer tank is implemented for heat storage.
Case studies were considered, consisting of a typical three-person household in the UK to investigate the present and the near-future capability of energy supplying and reduction of CO2 emission according to the UK building energy regulation.
Results show that single band-gap photo-electrode materials are not able to cover completely the energy demands for the household if demand includes space and hot water heating. However, with multiple band-gap electrodes and with extra solar heat (or combined PEC-thermal) utilization the system efficiency can be significantly increased.
Catalyst Durability in Low Temperature Polymer Electrolyte Fuel Cells
Authors: Stevenson Matthew , van Schalkwyk Francois , Levecque Pieter , Pattrick Gary , Conrad Olaf 
Published: February 2020

Durability in the context of commercial applications can be defined as the number of times that a counter is increased by 1 before a measure of performance reaches a threshold beyond which it is considered a fail. For catalysts in fuel cells the counter is often conveniently chosen to be either hours of operation or number of cycles and the performance threshold is typically some percentage of a beginning-of-life performance metric, such as specific activity or metal surface area. Degradation is the process of performance decline and this tutorial will highlight some of the current research trends in the study of degradation mechanisms and the strategies to mitigate the effect of degradation-inducing processes.
Most catalysts are multi-component systems comprising an electrically conducting support material, typically carbon black, and a catalytic material, typically platinum. Both are subject to degradation under most operating conditions, sometimes independently, but more often influenced by each other. The second half of the tutorial will present some of the recent advances in the increase of durability by varying the catalyst components.