bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Throughput Screening for Color in Electrochromic Devices
Authors: Sotzing Gregory 
Published: February 2020

Color selection for the transition between two color states within an electrochromic device can be a difficult and drawn out process involving careful molecular design of the chromophore, synthesis, and purification, followed by reiteration of this procedure should the desired color not be achieved. Here, we present a technique in which high-throughput screening of color for conjugated polymer electrochromics inside an electrochromic device. The techique involves co-diffusion of a monomer that would produce a high bandgap conjugated polymer with a monomer that would produce a low bandgap conjugated polymer within a polyelectrolyte to generate a diffusional gradient of both monomers between their points of introduction. This diffusional gradient of monomers is then converted to a gradient of random copolymers via an electrochemical oxidation producing nearly the entire subtractive spectrum of colors that can then be switched to a colorless state. Perpendicular orientation of this gradient to the electrochromic device allows for achievement of neutral coloration, important for tinting applications. Electrochromic devices of 171 cm2 active switch area have been optimized through optimization of the polyelectrolyte, and monomer choice for our solid-state conversion process of monomers to conjugated polymers to result in photopic contrasts as high as 58% without any substrate corrections. Photopic contrasts of 41% have been achieved for devices meeting military neutrality standards. As a further demonstration of our solid-state conversion, we have prepared all-spandex electrochromic devices in which the electrochromic device can be stretched during the color-change process. The spandex devices have the feel of spandex and could find applications in wearable displays and/or adaptive camouflage.
Spectroelectrochemical Study of the Role of Pyridinium in Carbon Dioxide Reduction
Authors: Lucio Anthony J , Shaw Scott K 
Published: February 2020

Pyridinium (pyrH+) has been studied for its potential catalytic role in the electrochemical reduction of carbon dioxide (CO2) to methanol. We report electrochemical analysis of the pyrH+ + CO2 interaction on metallic electrodes, independently of the hydrogen evolution reaction. Present results show that gold electrodes exhibit unique pyrH+ and CO2 electrochemistry compared with previous work on platinum electrodes or photochemical systems. Analysis of the electrochemical data show multi-layer adsorption of pyridine, an irreversible reduction wave associated with pyrH+ as the pH approaches the pKa of pyrH+, and a small but significant catalytic activity (0.15 mA/cm2) for CO2 reduction in the presence of pyrH+ at -1.0 V vs. Ag/AgCl.
The present work aims to discern the electroreduction mechanism by analyzing the proposed pyrH+ reduction process in inert purge gas environments using electrochemical and in situ infrared and Raman spectroscopic techniques. This information will guide the analogous exploration under CO2 environments to determine the nature of the enhanced current response. Possible products from the pyrH+ + CO2 electroreduction will be discussed.
In Situ UV-Vis Differential Reflectance Spectroscopy Study of Polycrystalline Platinum Oxidation in Aqueous Solutions
Authors: Xu Jing , Scherson Daniel 
Published: February 2020

A primitive model involving the combined use of coulometric and in situ differential reflectance spectroscopy data collected simultaneously1 has been applied to examine oxide formation on the surface of Pt(poly) electrodes in aqueous 0.1M HClO4 as a function of the applied potential. Analysis of experimental data assumed sequential formation of two different kinds of oxides, PtOH in the low and PtO, in the high potential regions, denoted as Ox1 and Ox2, respectively. The potential dependence of the coverages of each of these species, thetaOx1 and thetaOx2, was obtained by solving the following set of coupled equations:
The symbol thetabare in Eq.(1) represents the coverage of the bare, i.e. non-oxidized surface sites, Qn, is the charge determined from the integration of the oxide reduction peak following the method reported by Novak2 and the factor 2 in Eq.(2) accounts for the stoichiometry of the oxide. Lastly the symbol -deltaR/R =-[R(Eref)-R(Esam)]/R[Eref], R(Eref) and R(Esam) are the reflectance values recorded at the reference potential, Eref, set at 0.05 V, and at any arbitrary sampling potential, Esam, respectively3 represents the differential reflectance, where A(E), B(E) and C(E) are coefficients that account for changes in the optical signal of each of the types of sites induced by the applied potential.1

Shown in jagged line in Fig. 1 is a plot of -deltaR/R vs potential, E, for Pt(Poly) in 0.1M HClO4 recorded at a scan rate of 10 mV/s. The solid smooth line in this figure was obtained from the analysis of the model specified above which yielded values of thetaOx1, thetaOx2, and thetabare vs E, for Pt(poly) in 0.1M HClO4 in Fig. 2.

REFERENCES

A. J. J. Jebaraj, D. Scherson, Anal. Chem., 86, 4241, (2014).

D. M. Novak, B. Conway, J. Chem. Soc. Faraday Trans. 77, 234, (1981).

J. Xu, D. Scherson, Anal. Chem., 85, 2795, (2013).

Figure 1
(Invited) Activity Trends and Design Principles for Multi-Transition-Metal (Oxy)Hydroxide Oxygen Evolution Catalysts
Authors: Boettcher Shannon Wachter 
Published: February 2020

Oxygen evolution reaction (OER) catalysis limits the efficiency of H2 production through water electrolysis/photoelectrolysis, a route to large-scale energy storage. The factors governing the activity of OER catalysts are not well understood. We found Ni-Fe oxyhydroxides are the fastest known water oxidation catalysts under basic conditions when compared to others using a quantitative electrochemical-microbalance approach. In-situ electrical, photoelectron spectroscopy, x-ray diffraction, and electrochemical analyses on Ni1–x
Fe
x
OOH films show that the reaction mechanism relies on the local electronic structure of a Ni-O(H)-Fe active site. Experiments with rigorous exclusion of Fe electrolyte impurities reveal that, contrary to common belief, pure NiOOH is a poor OER catalyst. FeOOH was found to be a poor electrical conductor, explaining its low apparent OER activity. Measurements on Co1–x
Fe
x
OOH support the hypothesis that NiOOH and CoOOH provide a conductive host for the Fe-related active sites. In sum, these results establish a new activity trend for OER catalysts, opposite to previous ones, that informs catalyst design.
(1) Trotochaud, L.; Ranney, J. K.; Williams, K. N.; Boettcher, S. W. Solution-cast metal oxide thin film electrocatalysts for oxygen evolution. J. Am. Chem. Soc.
2012, 134, 17253.
(2) Trotochaud, L.; Young, S. L.; Ranney, J. K.; Boettcher, S. W. Nickel–iron oxyhydroxide oxygen-evolution electrocatalysts: The role of intentional and incidental iron incorporation. J. Am. Chem. Soc.
2014, 136, 6744.
(3) Burke, M. S.; Kast, M.; Trotochaud, L.; Smith, A.; Boettcher, S. W. Cobalt-iron (oxy)hydroxide oxygen evolution electrocatalysts: The role of structure and composition on activity, stability and catalytic mechanism. To be submitted
2014.
Structural Dynamism in Manganese Oxides in the Potential Regime for Water Oxidation: A SERS Study
Authors: Ranjan Chinmoy 
Published: February 2020

Non noble metal "earth abundant" electrocatalysts will significantly reduce the costs and make it possible to use electrochemical water splitting (electrolysis) on a very large scale. Non noble metal catalysts can be an effective replacement even if their electrochemical activities are a fraction of their noble metal counterparts. If these catalysts can be developed to an extent where their operational lifetime would become comparable to their noble metal counterparts, a large part of the problem would be solved. MnO2 is earth abundant and well known for catalyzing oxygen evolution. A form of MnOx cluster is known to catalyze water oxidation in photosynthesis. These catalysts although with immense potential remain a long way from successful implementation within electrolysers. In order to understand the limitations of this catalyst under the operational conditions, it is important to study this material in situ. Setup for in situ Surface Enhanced Raman Spectroscopy is used for tracking the structural changes of hydrous MnOx. Electrodeposition of MnOx on the surface of Au was achieved by passing an anodic current of 50 mC/cm2 at 1,6V.
The resulting MnO2 phase could be termed as the alpha/MnO2 phase. The structural integrity of the MnOx was studied by following the Mn-O-Mn stretching various potential ranges in various electrolytes. Onset of phase changes and corrosion could be clearly established. Beside this, other methods such as XRD, SEM, TEM were applied to study these thin films. Depending upon the nature of electrolyte the catalyst acquired a specific structure.

Figure 1
Perovskite Oxides Electrodes for Alkaline Oxygen Evolution Reaction
Authors: Sljukic Biljana , Martins Marta , Santos Diogo M.F. , Amaral Luis , Sousa Nuno , Sequeira Cesar A.C. , Figueiredo Filipe M 
Published: February 2020

Designing electrode materials for oxygen evolution reaction (OER) and for oxygen reduction reaction (ORR) is crucial for the development of renewable energy technology devices, such as water electrolyzers and fuel cells [1]. Alkaline water electrolysis is seen as an eco-friendly process for large-scale production of hydrogen required for hydrogen economy. However, the efficiency of water electrolysis in practice is limited by the large overpotential necessary to drive OER, resulting in high cost of the process and produced hydrogen.
There are few literature reports on OER at perovskite-based electrodes where different carbon supporting materials were often used for increase of active surface area and conductivity [1-3]. The aim of this study was to examine the intrinsic activity of perovskite materials.
Therefore, six different perovskite oxides were used for preparation of electrodes with no carbon support, to be studied for OER in alkaline media. These were La0.8Sr0.2Fe0.8Co0.2O3, La0.7Sr0.3MnO3, La2NiO4, La1.9Pr0.1CuO4, La1.8Pr0.2NiO4 and La1.9Sr0.1NiO4. OER studies were performed using cyclic voltammetry (CV) and linear scan voltammetry (LSV) in potassium hydroxide (KOH) solution. Main reaction parameters, namely Tafel slopes, charge transfer coefficients, exchange current densities, and activation energies were determined from the LSV data. Influence of operating parameters, specifically electrolyte composition and temperature, was also investigated.
First results indicated the highest activity of La1.9Sr0.1NiO4 for the OER in the studied temperature range (25 – 85 ºC).
References
[1] M. Risch, K. A. Stoerzinger, S. Maruyama, W. T. Hong, I. Takeuchi, Y. Shao-Horn, J. Am. Chem. Soc. 136 (2014) 5229 − 5232.
[2] C. Jin, X. Cao, L. Zhang, C. Zhang, R. Yang, J. Power Sources 241 (2013) 225 – 230.
[3] R. A. Rinc, E. Ventosa, F. Tietz, J. Masa, S. Seisel, V. Kuznetsov, W. Schuhmann, ChemPhysChem 15 (2014) 2810 – 2816.
Nanoengineering of MoS2 Electrocatalysts for Efficient Hydrogen Evolution Reactions
Authors: Gao Qingsheng , Liu Ning 
Published: February 2020

Advanced catalysts with element-abundance, economic-cost and stability are desired for electrochemical hydrogen evolution reaction (HER) to scale-up the promising clean energy of hydrogen.[1] The discoveries in the (de)hydrogenation of petroleum chemicals have inspired several efficient and economic catalysts of metal non-oxides towards HER, such as Mo-based sulfides and carbides.[2] MoS2 possesses a layered structure exposing Mo- and S- edges, which are highly active for HER due to the moderate hydrogen bonding energy (ΔGH*).[3] However, its performance is still limited by the poor conductivity and the uncontrolled properties of active-sites.
In our recent work, efforts have been made to synergically enhance the conductivity and active-site abundance of MoS2, achieving the high current densities and low onset overpotentials for HER.[4-6] For example, we proposed a new route to confine MoS2 growth within an in-situ formed polysaccharide matrix from glucose condensation during hydrothermal processes, and after the following carbonization, MoS2/C nanocomposites evenly integrating ultrathin MoS2 nanosheets (2 ~ 4 nm) with conducting carbon were successfully harvested (Fig. 1a).[6] The MoS2/C exhibited an excellent HER activity characterized by higher current densities and lower onset overpotentials than the conventional MoS2. In particular, the MoS2/C with a suitable MoS2 content of 14.8% showed a small onset overpotential of ~80 mV, a high current density of 88 mA cm-2 at η = 200 mV, which are ascribed to the abundant rim-sites on ultrathin MoS2 nanosheets and the improved conductivity by carbon. On the other hand, a facile microwave-assisted hydrothermal method was further introduced to fabricated active-site enriched MoS2 nanosheets employing reactant self-shelter, in which the excessive S source (e.g., thiourea) would cover the highly-active Mo-sites during MoS2 formation, and then be removed by following treatment with H2SO4, resulting in abundant active sites on MoS2. The electrocatalytic test well-confirmed the significantly improved active-sites (~3 orders) and conductivity as compared with the traditionally prepared MoS2. Thanks to the facile synthesis and outstanding electrochemical behaviors, our effort is expected to pave the way for earth-abundant, economic and efficient electrocatalysts used in energy conversion and storage.
References:
[1] A. B. Laursen, S. Kegnaes, S. Dahl, I. Chorkendorff, Energy Environ. Sci., 2012, 5, 5577.
[2] C. G. Morales-Guio, L. Stern and X. L. Hu, Chem. Soc. Rev., 2014, 43, 6555.
[3] T. F. Jaramillo, K. P. Jorgensen, J. Bonde, J. H. Nielsen, S. Horch, I. Chorkendorff, Science, 2007 317, 100-102.
[4] L. C. Yang, S. N. Wang, J. J. Mao, J. W. Deng, Q. S. Gao, Y. Tang, O. G. Schmidt , Adv. Mater., 2013, 25, 1180.
[5] Q. S. Gao, N. Liu, S. N. Wang, Y. Tang, Nanoscale, 2014, 6, 14106.
[6] N. Liu, L. C. Yang, S. N. Wang, Z. W. Zhong, S. N. He, X. Y. Yang, Q. S. Gao, Y. Tang, J. Power Source, 2015, 275, 588.

Figure 1
Water Splitting Using Gallium Nitride Based Working Electrodes for Hydrogen Generation without Applying Bias
Authors: Chen Yen Yu , Sheu Jinn Kong , Lai Wei Chi , Lee Ming Lun 
Published: February 2020

In this study, we demonstrated photoelectrochemical(PEC) hydrogen generation using InGaN-based semiconductors as the working electrode for water splitting under solar illumination. For a working electrode made of n-type semiconductor, the holes drive the oxidation of water on the photoelectrode, and the electrons transport within semiconductor and in turn move to the cathode electrode leading to the reduction reaction. Although GaN is potentially resistant to aqueous solution and its energy band is suitable for water photoeletrolysis, GaN only absorbs UV light which is about 5% of the solar spectrum. The bandgap energy of the InxGa1-xN can be tuned from 0.7eV to 3.4eV by changing the Indium content to fit the most of the terrestrial solar spectrum. Therefore, InGaN-based working electrodes for water splitting are expected to be more efficient than the GaN working electrodes.
The working electrodes used in this study featuring meshed metal contacts with SiO2 protection layer were immersed in electrolyte to enhance the collection efficiency of photogenerated carriers. On the other hand, the generation rate of hydrogen could be improved by applying external bias onto the working electrodes to enhance the separation of photogenerated electron-hole pairs in the semiconductor and the charge transfer at the interface between semiconductor and electrolyte during the PEC water splitting process. However, the external bias on PEC water splitting requires extra input power except light illumination. In this study, InGaN-based semiconductors associated with meshed metal contacts were served as working electrodes without external bias to conduct the PEC water splitting process under the light illumination.
Instead of using an external bias provided by power supply, a solar cell was used to raise the driving force to increase the rate of hydrogen production. The solar cell was connected in series between the InGaN-based working electrode and the platinum (Pt) counter electrode to bias the PEC cell. In principle, the water splitting for generating hydrogen involves two mechanisms during the light illumination if the solar cell supplies bias voltage larger than 1.23 V. The mechanisms are photoelectrolysis and electrolysis of water splitting. To solely evaluate the efficiency of photoelectrolysis or electrolysis of water splitting, the output voltage of solar cell was varied through changing the type of solar cell to allow the PEC cell with bias less or larger than 1.23 V. The preliminary results indicated that the hybrid working electrodes exhibited a marked improvement in the efficiency of hydrogen generation.
The detailed results will be presented in the forthcoming conference.

Figure 1
Organophotocatalyst Films and Their Multilayerization That Efficiently Utilize Natural Sunlight
Authors: Nagai Keiji , Abe Toshiyuki , Iyoda Tomokazu 
Published: February 2020

A full-spectrum visible-light-responsive organophotocatalyst membrane array is designed and employed for a one-pass-flow water purification system. Whereas previous photocatalyst systems required strong light source, the present design manages with natural sunlight intensity, owing to multi-layerization of a newly optimized low-absorbance organophotocatalyst. The design of the system is to utilize natural-sunlight-equivalent visible light with 1 m2 of irradiation area to process 1 ton/day of water. A 1/3300 scale module of the system was constructed and experimentally demonstrated its viability. The reactor part of the flow system contains 24 stacked layers of organic-semiconductor-laminated Nafion film. The organic semiconductor is a bilayer of metal-free phthalocyanine (H2Pc, p-type semiconductor) and 3,4,9,10-perylenetertacarboxylic-bisbenzimidazole (PTCBI, n-type semiconductor). Transparent Nafion functions as mechanical support and absorbent of trimethylamine, which was chosen as a typical contaminant of underground water in coastal areas. The reactor was irradiated for only 1 h/day by visible light (10 mW/cm2). The light intensity at the bottom layer was estimated to be 0.1 mW/cm2, which was sufficient intensity (Internal quantum efficiency was 0.15.) for the photocatalytic reaction, due to the optimized absorbance and photocatalytic quantum efficiency of each layer. The inlet TMA concentration was 3 ppm, while that of the outlet was less than 0.03 ppm for the first day of the operation of the system with and without the bilayer. Without the bilayer, the TMA concentration of the outlet flow increased after the 20 days. With the bilayer, the TMA concentration of the outlet flow remained at less than 0.03 ppm for the 40-day experimental period due to its photocatalysis. The turnover number of photocatalytic reaction was calculated to be 1.8×104.
References: [1] K. Nagai et al, ACS Sus. Eng. Chem. 1, 1033 (2013). [2] K. Nagai et al, ChemSusChem. 4, 727 (2011). [3] T. Abe et al., Chem. Commun, 50, 1950, (2014).
Prospects for Future Photoelectrolysis Devices: New Oxide Semiconductors and Electrode Structures
Authors: Parkinson Bruce A 
Published: February 2020

The full potential of solar energy cannot be realized unless there is method to store it and use it as fuel. In this talk I will give both a brief historical look at the past efforts to solve this problem and provide some options and opinions about the way forward. It is clear that materials that are stable and have the proper band gaps for an efficient photoelectrochemical water splitting device are currently unknown. In addition these materials need to be catalytic for water oxidation or reduction reactions or have catalyst layers deposited on their surfaces. I will discuss combinatorial methods for discovering new oxide semiconductors and solid-state catalysts that might be further optimized to be useful in a solar water splitting device. Researchers need to focus on quickly evaluating the many new materials that will emerge from the combinatorial searches to identify a few that have the potential to be stable, efficient and inexpensive. An example of a new semiconducting oxide containing earth abundant iron, chromium and aluminum that was discovered by an undergraduate researcher participating in the Solar Hydrogen Activity research Kit (SHArK) project will be given. Thie photoelectrochemical behaviour of this material was followed up in our laboratory and found, after optimization of the stoichiometry, to have a high open circuit voltage for water reduction. An example of collaborations between my laboratory and other laboratories to quickly evaluate the potential of this material will be given as an example.
Role of Surface Amorphization in CuO-Cu2o Core-Shell Nanowire Array for Photoelectrochemical Water Splitting
Authors: Wu Fei , Banerjee Sriya , Myung Yoon , Banerjee Parag 
Published: February 2020

We demonstrate spatial (i.e., where) and stoichiometric (i.e., how much) control of dense CuO core - Cu2O shell nanowires (NWs). These NWs are then used as photocathodes for water splitting. CuO has a narrower band gap (1.53 eV) and a higher conduction band edge compared to Cu2O (2.0 eV), thus enabling an efficient way to absorb light and convert solar energy.
Thermally grown CuO NWs under carbothermal reduction conditions lose oxygen from the surface.[1] The out-diffusion of oxygen makes single crystalline CuO transform to Cu2O. However, a 2 to 3 nm transition, amorphous Cu2O layer on the surface is formed. This transition, surface amorphous Cu2O layer crystallizes under longer reduction time. We tune the CuO core/Cu2O shell ratio by controlling the temperature and time of reduction to study the CuO NW phase transformation kinetics. We examine the phase transformation (oxygen loss) in the NWs using Raman spectroscopy and model it within the framework of the Johnson-Mehl-Avrami equation. The nature of the transformation under oxygen loss conditions in narrow 1D NWs will be presented.
The as-synthesized CuO-Cu2O core-shell NW array is systematically used to examine water splitting performance. The maximum photocurrent density measured is 2.69 mA/cm2 at 0.6 V vs. Ag/AgCl for the CuO-Cu2O core-shell NW structure with a 2-3 nm transition, surface amorphous Cu2O layer. Once the amorphous layer crystallizes, photocurrent density decreases to 0.3-0.4 mA/cm2 range. This data indicates that amorphous protection layers can improve the photocathodic performance CuO NWs.

[1] Wu, F. Myung, Y. Banerjee, P. Cryst. Growth Des.
2014,
10.1021/cg500784y.
Ion-Conduction within the Fibrous Framework of an Electrospun PEO Gel Electrolyte
Authors: Moore Robert B 
Published: February 2020

Poly(ethylene oxide) (PEO) containing pentaerythritol triacrylate (PETA) was electrospun to yield fiber mats that were subsequently crosslinked by exposure to UV irradiation. These mats were then supplemented with lithium perchlorate and swollen with ethylene/dimethyl carbonates to generate a structured polymer-gel electrolyte for Li-polymer battery applications. The fibrous mats were found to be composed of a nonwoven collection of ca. 1μm diameter PEO fibers with up to 85% porosity. Prior to UV exposure, the mats were completely soluble in polar solvents. However, following UV exposure, the mats were rendered insoluble by chemical crosslinking, yielding gel fractions in excess of 80%. Upon incorporation of a liquid lithium ion electrolyte, the swollen mats were shown to maintain the fiberous framework and exhibit conductivities as high as 1.2 × 10-2 S/cm at room temperature. In contrast, a control mat of electrospun poly(vinylidene fluoride) containing fibers of comparable dimensions and identical electrolyte loading was found to yield a conductivity of only 5 × 10-3 S/cm. NMR methods to probe further details of the transport properties of these new electrolytes will also be expored.