bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi-Color Electrochromic Devices Based on Phenyl and Heptyl Viologens Immobilized By an UV-Cured Polymer Electrolyte
Authors: Chang Ting-Hsiang , Kao Sheng-Yuan , Kung Chung-Wei , Lee Minhan , Lu Hsin-Che , Ho Kuo-Chuan 
Published: February 2020

Over the last few decades, viologens have been applied for electrochromic devices (ECDs). However, viologens are soluble in water or polar organic solvent and solution-type viologens suffer from leakage problem. To tackle this issue, many strategies have been proposed for preparing immobile viologens. In this study, an UV-crosslinked ethoxylated trimethylolpropane triacrylate (ETPTA) polymer network and succinonitrile (SN) were employed to prepare a solid polymer composite electrolyte (PCE) matrix [1] at room temperature to immobilize heptyl viologen (HV) and phenyl viologen (PV) at the electrode surface. PV exhibits good EC property, while aggregation of PV occurs immediately utilizing conventional liquid or gel electrolyte due to strong π-π stacking. Herein, an all-solid-state ECD is proposed to solve aggregation issue of PV. Moreover, a multi-color ECD is fabricated by incorporating HV, PV, and PCE. By changing the operating potential, the ECD exhibits green, blue, gray color at 0.6 V, 0.8 V, and 1.0 V, respectively (Fig. 1). The first set of redox peaks in Fig. 1 is due to redox reaction of PV, and the second set of redox peaks is the overlap of first reduced state of HV and second reduced state of PV. Fig. 2 shows the dynamic transmittance change of the proposed ECD between 0 and 1 V. The increment in transmittance at 1 V is due to the second reduced state of PV and HV at 438 nm and 610 nm, respectively. The color-tuning of the proposed ECD is controlled by the ratio of HV and PV molecules immobilized on the electrode surface, which can be explained by the coloration efficiency and cyclic voltammogram of the ECD.

Figure 1
Surface Treatments for Electrochromic Glazing: Toward Reduced Costs and Optimal Performances through Ultrasonic Spray Pyrolysis
Authors: Maho Anthony , Denayer Jessica , Bister Geoffroy , Aubry Philippe , Colson Pierre , Henrist Catherine , Cloots Rudi 
Published: February 2020

Research and industrial interests for electrochromic “smart” windows have considerably grown those recent years due to their potential use as an energy-saving material for buildings. Their CO2 emission can be significantly reduced by decreasing their energy consumption up to 30%.
The crucial issues of such devices are the coloration efficiency as well as the reversibility upon coloration and bleaching of the electrochromic layers. The combination of WO3 and Li-doped NiO surface films (separately as working and counter electrodes) affords a good coloration contrast between colored and bleached states of the device, since tungsten oxide colors upon electrons and ions insertion while nickel oxide gets colored after their extraction.
In order to improve the performances of those electrochromic films, we have studied the effects of a surfactant-assisted deposition process of both individual layers through Ultrasonic Spray Pyrolysis (USP). This technique indeed constitutes a low-cost alternative to industrial vacuum processes for manufacturing high quality thin films.
The crystallization and morphology of those films, as well as their optical, electrochromic and electrochemical properties have been investigated. The presence of surfactant in the precursor solution has led to improved wetting of liquid droplets sprayed on the heated FTO/glass substrate. The resulting films testify for a better homogeneity and a higher active surface, which also allows for enhanced reversibility and coloration contrast.
Enhanced Electrochromic Performance Based on Conducting Polymer/ZnO Nanocomposites
Authors: Lv Xiaojing , Zhang Cheng 
Published: February 2020

Conducting polymers have been increasingly studied owing to their diverse colors, high optical contrast, fast switching speed and good processibility for various electrochromic (EC) applications, such as smart windows, reflecting mirrors and thin flat panel displays. However, practical applications need to meet several requirements, including a multicolor display, ultrafast switching speed and excellent long-term stability. Conducting polymer-inorganic nanocomposite has drawn more attention since they can combine the advantages of both components, and may offer special properties through the reinforcement or modification of each other.1-2 In this paper, conducting polymer/ZnO nanocomposites were fabricated via solvent thermal or electrodeposition combining with electropolymerization method. The effect of different ZnO nanostructures (such as nanoridges, nanorods, nanosheets) on the properties of electrochromic composites were investigated. The results demonstrate that the electrochromic performances of conducting polymers are significantly enhanced by incorporating with different ZnO nanostructures. Moreover, the possible mechanism for the enhanced properties is proposed that the introduction of ZnO nanostructures can shorten the diffusion distance and provide larger contact area, which facile the ion doping/dedoping and enhance the adhesion between the polymer and the electrode, resulting in higher optical contrast, faster switching speed and more excellent electrochemical stability.

References

1. K. Choi, S. J. Yoo, Y. E. Sung, R. Zentel, Chem. Mater.,
18
, 5823 (2006).
2. R. J. Mortimer, A. L. Dyer, J. R. Reynolds, Displays, 27, 2 (2006).

Figure. 1 SEM photos and the contrast of elelctrochromic properties between polymer and nanocomposite

Figure 1
in Situ Coherent Surface x-Ray Scattering Study of the Au (111) Surface Dynamics in Electrolytes: The Effect of Surface Reconstruction and Chloride Adsorption
Authors: Liu Yihua , Barbour Andi , Komanicky Vladimir , You Hoydoo 
Published: February 2020

It has long been conceived that in equilibrium electrode surfaces in contact with electrolytes remain highly dynamic, exhibiting steady processes such as detachment and adsorption of surface atoms. Importantly, some of those microstate fluctuations play an essential role on formation of surface structure and composition, and ultimately affect the functionality of electrodes. Surface-sensitive techniques, like STM and surface x-ray scattering (SXS), have become invaluable to unraveling electrode surface structures under changing electrochemical environments. Measurements on surface dynamics, however, remain challenging for electrochemical systems [[1]].
In this talk, we will report on the study of Au (111) surface dynamics by coherent surface x-ray scattering (CSXS). A brief introduction will be given for implementation of CSXS and ISXS for electrochemical studies. Time-resolved capability of CSXS will be highlighted.
To elucidate factors that could influence surface dynamics, Au (111) electrode surfaces are systemically tailored by varying electrochemical conditions. Phase transition in Au (111) electrode surface had been well characterized by SXS, with structural changes that were shown to be both dependent on potentials and solution chemistry [[2]]. A sharp drop in x-ray scattering intensity around 0.12 V, shown in Fig. 1 (black curve), marks phase transition from (p x√3) to (1x1), which then can be reconstructed back to form a (p x√3) structure in a reverse potential scan. A similar potential dependence is found with increasing chloride concentration as shown in Fig. 1 (red curve). Careful comparison of the hysteresis loops, presented in Fig. 1, additionally reveals that chloride concentration influences the kinetics of phase transition in Au (111) surfaces.
In additional to structural details, we have also attained some preliminary results on the dynamics of Au (111) surfaces from CSXS experiments. In the present work, surface dynamics are quantified in terms of correlation time, a parameter that describes the temporal separation between two configurations that are no longer resemble each other due to microstate fluctuations. Correlation time in relation to surface structure will be shown and discussed as a function of applied potential and chloride concentration. A comprehensive analysis on surface dynamics will be performed to help establish its relations with surface structure and solution chemistry.

[1] M. Pierce, V. Komanicky, A. Barbour, D. C. Hennessy, C. Zhu, A. Sandy, H. You, Phys. Rev. B
86, 085410 (2012).
[2] J. Wang, B.M. Ocko, A. J. Davenport, H. S. Isaacs, Phys. Rev. B
46 10321 (1992).

Figure 1
Vanadium Nitride Thin Films and Nanoclusters: Growth and Electrochemical/XPS Characterization
Authors: Bondarchuk Oleksandr , Goikolea Eider , Rojo Teofilo , Mysyk Roman 
Published: February 2020

Pseudocapacitive or electrochemically active materials can achieve capacitance values up to 10-100 times greater than those obtained by materials based only on an electric double layer (EDL) mechanism. The pseudocapacitive behavior of transition metal oxides has been extensively studied in the last decades and assigned to redox reactions occurring at the surface of the material. Very recently, transition metal nitrides such as MoxN, VN or TiN have emerged as promising electrode materials for electrochemical capacitors. These materials are inexpensive, have a high molar density good chemical resistance and, most importantly, in contrast to oxides they exhibit very high electronic conductivity value. Extremely high specific capacitance values of 1340 F g-1 was reported for nanostructured VN [1]. To shed some light on the mechanism of such huge capacitance we have carried out a comparative study of VN thin films and VN nanoclusters grown and characterized in-situ to relate electrochemical properties with the structure and composition of the surface of vanadium nitride.
An UHV system (SPECS) equipped with tools for XPS, e-beam assisted evaporation of metals, high pressure cell and electrochemical cell for I-V cycling was used for in-situ synthesis and characterization.
A recipe to grow VN thin films and nanoclusters via direct nitridation of thin vanadium film in atmosphere of 1 bar N2 at temperature 800 oC has been developped. Stoichiometry of the VNxOy compounds can be controoled by post oxidation of VN in oxygen atmosphere at elevated temperature. Growth of VN nanoclusters using the same procedure has been performed on HOPG surface.
Electrochemical characterization of VN and VNxOy thin films demostrated impressive areal capacitance of ~2000 µFcm-2 in 1M KOH electrolyte at scan rate 1Vs-1. XPS characterizationwas applied to elucidate electrochemical reactions occurring on the surface of VN films.
[1] D. Choi et al., Adv. Mater., 18, 1178 (2006)
Catalytic Activity of Doped Praseodymium and Samarium Based Perovskites in Hydrogen and Oxygen Evolution Reactions
Authors: Kolla Praveen , Schrandt Matthew , Smirnova Alevtina 
Published: February 2020

Over the last decades, the ABO3 perovskites have been extensively studied as active catalyst materials for various low and high temperature redox reactions; e.g. hydrogen or oxygen evolution reactions and internal and biomass reforming. However, the mechanisms of their catalytic/electrochemical activity and stability vs. A- and B-site doping especially in aqueous solutions have not been clarified yet. Furthermore, it is not clear how the oxygen deficiency created in doped perovskites (e.g. AA’BB’O3-δ) by partial substitution of less valent cations on A- and/or B-sites contributes to their oxygen exchange redox behavior at ambient conditions. In this regard, a comparative study of the PrNixCo1-xO3-δ and SmNixCo1-xO3-δ catalytic behavior was performed considering possible applications related to electrochemical and thermochemical hydrogen/oxygen evolution
PrNixCo1-xO3-δ and SmNixCo1-xO3-δ, where x= 0.1, 0.5, 0.9, were synthesized using a modified nitrate-glycine Pechini method (1) followed by a heat-treatment in air at 700oC, 900°C and 1200°C. X-ray diffraction patterns reveal that the formation and chemical stability of the perovskite phase depends on the nature of the lanthanide element (A), relative composition of Ni to Co, and the heat-treatment temperature. For example, praseodymium based perovskites are more stable at higher heat-treatment temperatures (1200oC) than SmNixCo1-xO3-δ. Furthermore, formation of the perovskite-phase (Fig. 1) is favorable at low Ni/Co ratios (x=0.1and 0.5) resulting in rhombohedral single-phase crystal structure. On contrary, high Ni/Co ratio (x=0.9) do not yield the perovskites phase.
The SEM and BET single point specific surface area (SSA) approaches were applied to determine the materials morphology. The HER and OER electrochemical performance was evaluated from cyclic voltammetry. A combination of Temperature Programmed Reduction/Oxidation (TPRO) and Thermo-Gravimetric (TG) analysis was further employed to understand their catalytic activity towards thermochemical hydrogen evolution.
In order to improve the electronic conductivity, the perovskite-graphene composites were synthesized by mixing the perovskites with graphene platelets (90 wt. %). The HER and OER electrochemical performance of PrNixCo1-xO3-δ and SmNixCo1-xO3-δ was studied in three-electrode configuration in alkaline medium. The structure-dependent electrochemical behavior of these nanocomposites as a function of nickel to cobalt molar ratio (x= 0.1, 0.5) and the heat-treatment temperature will be discussed in terms of Tafel plots, chemical stability, and potential applications in comparison to the state-of-the-art catalysts.
Acknoledgements: The authors gratefully acknowledge the financial support from the ACS Petroleum Research Fund (Project number 53614-UR10) and the NSF EPSCoR support (Awards IIA-1330840 and IIA-1330842).
References: 1. M. C. Schrandt, P. Kolla and A. Smirnova, MRS Online Proceedings Library, 1542 (2013).

Figure 1
Modeling of Bio-Electrochemical and Mechanical Interactions in a Photosynthetic Cell
Authors: Hemanth Kumar Tanneru , Resmi Suresh M.P , Ramanan Aravind Vyas , Mehdi Shahparnia , Muthukumaran Packirisamy , Pillay Pragesan , Williamson Sheldon S , Rengaswamy Raghunathan 
Published: February 2020

Micro photosynthetic cell (µPSC) is an electrochemical device, which generates electricity, by harnessing the electrons from photosynthesis and respiration processes of the photoautotrophs.
Till date, focus has been mostly on experimental aspects of and very little work has been pursued on the development of mathematical models for µPSC. Modeling a system like µPSC is complex due to the fact that the device operation depends on interactions of microorganisms with several operational parameters such as light intensity, quantum yield and so on. Further, the electrode structure and the electrochemical interactions at the surface of the electrodes affect the device performance.
Modeling of µPSC could help in understanding the performance limiting step(s) in the series of processes that occur during the operation of device. The performance of the device can be improved by focusing on the rate of limiting steps. Modeling could also help in determining optimal design and operational parameters which can maximize the device performance.
A simple mathematical model based on first principles is proposed to predict the performance of the µPSC. Sensitivity analysis is performed to obtain the most sensitive rate parameters of the model. The optimal values of sensitive rate constants are obtained from the experimental data through optimization. The developed model is validated by comparing the predictions of the model with the experimental data obtained from the response of the system to step changes in load. Figures 1 and 2 show the model performance in terms of i-V characteristics and comparison of experimental and estimated voltage profiles for step changes in external loads.
Keywords:, First principles model, Parameter estimation, and Optimization and Sensitivity analysis.

Figure 1
Benchmarking Components for Photoelectrochemical Water-Splitting Devices
Authors: Chatman Shawn M , McCrory Charles C L , Peters Jonas C , Jaramillo Thomas F 
Published: February 2020

Objective evaluation of solar energy conversion efficiencies is of fundamental importance to the development of solar energy driven photoelectrochemical (PEC) water-splitting devices. Unfortunately there is no current standard methodology for evaluating the efficiency of fuel-forming PEC components and devices. Consequently, in the literature, there is a wide array of testing procedures and calculations being used to report device and component efficiency. Here we will highlight some of the common testing procedures and efficiency calculations being used, pointing out important areas where there is no universal agreement. In addition, we will present the testing procedure used within the Benchmarking facility of the Joint Center for Artificial Photosynthesis (JCAP). We illustrate our procedure by presenting pertinent photoelectrochemical data collected from measurements taken on well-known PEC water-splitting components and devices (e.g. Pt/p-Si, Ni/BVO, triple junction Si, p-GaP, p-InP, n-TiO2) and explain how this data can be translated into real world device-pertinent figures-of-merit.
IrO2 Surface and Nanostructure Stability from First Principles and Variable Charge Force Field Calculations
Authors: Sen Fatih G. , Kinaci Alper , Narayanan Badri , Davis Michael J. , Gray Stephen K. , Sankaranarayanan Subramanian K. R. S. , Chan Maria K. Y. 
Published: February 2020

IrO2 is one of the most efficient water-oxidation electrocatalysts and can also act as a photocatalyst for the water splitting reaction when used in the form of nano-sized clusters. The structure and surface properties of nanoclusters greatly influence the photocatalytic properties of IrO2, and atomistic scale understanding of these properties is essential to elucidate the photocatalytic mechanisms of IrO2. Here, we carried out first principles calculations based on spin polarized density functional theory (DFT) including spin-orbit coupling and the Hubbard U correction on the bulk and surface structures of IrO2. The stability and electronic structure of low index rutile (100), (001), (110) and (101) surfaces of IrO2, were studied. The relative surface energies were obtained as (110) < (101) < (100) < (001). The equilibrium shape of IrO2 nanoparticles was deduced using a Wulff construction. In order to study the structural stability of IrO2 nanoclusters and the long time-scale dynamics of IrO2 polymorphs larger than about 2 nm in diameter, we developed the first empirical interatomic potential (force field) for IrO2 based on Morse functional form coupled with a variable charge method (QEq). The Morse+QEq parameters were optimized using an evolutionary algorithm with respect to a DFT training set, and was shown to be successful in predicting bulk and surface properties of rutile IrO2 and various polymorphs including anatase, brookite, columbite and pyrite derived from DFT calculations. Pressure induced phase transformations of bulk IrO2 polymorphs were reported and thermodynamically stabile phases of IrO2 at nano-scale were obtained using the surface energies of stable polymorphs. Our results will shed light on the development of stable nanoscale IrO2 electrocatalysts and photocatalysts that can efficiently utilize solar energy for water splitting reaction.
Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
Thin Film Photovoltaics with Organic Metal Halide Peroviskites
Authors: Kamat Prashant V 
Published: February 2020

Organic metal halide perovskites have now emerged as new and promising candidates for developing low cost thin film solar cells with efficiencies in the range of 20.1% certified efficiency. The recent advances of CH3NH3PbI3 based thin film solar cells have manly focused on the design architecture and improving the stability. Both TiO2 and Al2O3 mesoscopic architectures provide robust support to design high efficiency thin film solar cells. The excited state dynamics leading to the charge separation remains to be fully understood. Through comparative spectral analysis between the absorption features of charge transfer complexes in the solution phase and the final solid-state perovskite films, we are able to fully classify the absorption features in the excited state of CH3NH3PbI3 across the transient absorption spectrum recorded following laser pulse excitation. The excited state of CH3NH3PbI3 characterized through transient absorption spectroscopy show dual behavior, viz., charge transfer complex state and charge separated state.1,2 The interplay between these two different excited states leads to efficient charge separation. Insights into the charge recombination kinetics and band filling aspects of CH3NH3PbI3 provide new ways to tune the efficiency of perovskite solar cells. These spectroscopic studies provide further insight into the optoelectronic behavior of methyl ammonium lead iodide films. Excited state properties that elucidate the exceptional photovoltaic properties will be discussed.
Acknowledgments
The research described herein is supported by the Office of Basic Energy Sciences, U.S. Department of Energy.

Selected Publications

Christians, J. A.; Fung, R.; Kamat, P. V., An Inorganic Hole Conductor for Organo-Lead Halide Perovskite Solar Cells. Improved Hole Conductivity with Copper Iodide. J. Am. Chem. Soc.
2014,
136, 758–764.

Manser, J. S.; Kamat, P. V., Band Filling with Charge Carriers in Organometal Halide Perovskites. Nature Photonics
2014, DOI: 10.1038/NPHOTON.2014.1171.
Novel Photoelectrodes and Noble Metal Free Catalysts for Light Driven Water Electrolysis
Authors: Fiechter Sebastian 
Published: February 2020

The generation of fuels from sunlight and water is considered as a task of paramount importance for a sustainable energy supply in the future. Decomposition of water by a photoelectrochemical process is a possibility to harvest solar energy in form of hydrogen in a large scale. For this purpose, a membra­ne can be used which immersed in an aqueous electrolyte and illuminated by sunlight is able to split water into hydrogen and oxygen. Such a device is frequently addressed as artificial leaf. From an eco­nomic and environmental point of view this device should consist of cheap, abundant and non-toxic elements featuring a Solar-to-Hydro­gen (STH) efficiency > 10% and generating hydrogen at a price of ~3 €/kg H2.
In our lab two approaches have been pursued in the last time to realize artificial leaf type structures:

triple junction thin film a-Si/µc-Si solar cells in superstrate geometry with integrated catalysts [1],

tandem junction solar cells combined with novel semiconducting ternary metal oxide anodes [2].
As photoanode materials Fe2WO6 and BiVO4 are under investigation and have been improved with re­spect to their photovoltage and their photocurrent densities using sol-gel and spray pyrolysis as prepa­ration technique. To lower the costs of the device platinum was replaced by carbon supported MoS2 nanoparticles as hydrogen evolving catalyst. Deposited as a blend with PEDOT:PSS on the backside of the solar cell an SHE of 3.7% was yielded. RuO2 was replaced by manganese and cobalt oxide thin films, respectively.
References:
[1] Diana Stellmach, Peter Bogdanoff, Onno Gabriel, Bernd Stannowski, Rutger Schlatmann,
Roel van de Krol, Sebastian Fiechter; FORMATEX 2013, 880-886.
[2] Fatwa F. Abdi, Lihao Han, Arno H.M. Smets, Miro Zeman, Bernard Dam, Roel van de Krol, NATURE COMM. 2013, 4:2195, DOI: 10.1038/ncomms3195.

Figure 1