bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasmonic Hydrogen Evolution Reactions Driven By Visible Light Illumination at p-Type Semiconductor Electrodes
Authors: Minamimoto Hiro , Sato Daiki , Murakoshi Kei 
Published: May 2020

The efficient control of the visible light driven hydrogen evolution reaction can be recognized as the one of the promising challenge for the sustainable society. It can be said that the wide-band semiconductor electrode is the good material for the photo-energy conversion system. However, various semiconductor electrodes have the limitation to the ultraviolet region because of their wide band gap energy. Recently, plasmoic photoelectric conversion system, which is the combination of the plasmon active metal nano-structures with the semiconductor electrodes, has been received much attention because the system shows the visible light response characters beyond its limitation. In this system, the electrons excited in the metal structures injected into the conduction band of the n-type semiconductor and the remained holes are consumed through the oxidation reaction. Up to now, various plasmon-induced chemical reactions, even the water splitting, have been proposed. As our previous study, we have not only visualized the reaction active sites but also determined the absolute electrochemical potential of the reaction active species through the polymerization reactions of the conductive polymer.1 Although well-established systems have been reported, the direct control of the reduction reaction at the metal-semiconductor interface by the excited electrons has not been well examined. This is because the almost plasmonic photoconversion systems consist of the n-type semiconductor electrode and applied the generated holes to the reactions. In this study, we have tried to establish the plasmon-induced hydrogen evolution system by the introduction of the plasmon-active metal nano-structures into the p-type semiconductor electrodes. By supporting the plasmonic structures, we have confirmed the photo-current generations under the visible light illumination. Through the photocurrent measurements and the incident photon to current conversion efficiency obtained under different pH conditions, we have confirmed the unique pH dependence. In addition to these, we have also investigated the isotopic effect on the hydrogen evolution reaction to clarify the unique surface molecular process.2 Through the various photoelectrochemical measurements, we are sure that our plasmonic hydrogen evolution system could be considered as one of the good candidate for future light energy conversion system.
Reference
1. Minamimoto and K. Murakoshi et al., J. Phys. Chem. C., 120(29), 16051 (2016).
2. Minamimoto, R. Osaka, and K. Murakoshi, Electrochimica Acta, 304(1), 87 (2019).
(Invited) Nanostructured Layered Double Hydroxide Based Photocatalysts for Solar Fuels and High-Value Chemicals
Authors: Zhang Tierui 
Published: May 2020

In this presentation, some very recent research progress in my group will be reported on the rational design of nanostructured layered double hydroxides (LDHs) based photocatalysts with heterointerface active sites for photoreduction of CO2 or CO into high value-added hydrocarbons with high selectivity, originating from the adjusted reaction pathway of intermediates. For instance, by constructing heterogeneous interface structure, NiO/Ni nanocatalysts exhibited an unexpectedly high selectivity of 60% for C2-C7 hydrocarbons in the CO hydrogenation reaction under visible-light irradiation.[1-8]

References
1. T. Zhang, et al., Adv. Mater. 2018, 30 (3), 1704663.
2. T. Zhang, et al., Adv. Mater. 2017, 29 (42), 1703828.
3. T. Zhang, et al., Adv. Mater. 2017, 29 (27), 1700803.
4. T. Zhang, et al., Adv. Mater. 2017, 29 (16), 1605148.
5. T. Zhang, et al., Adv. Mater. 2016, 28 (43), 9454-9477.
6. T. Zhang, et al., Angew. Chem. Int. Ed. 2016, 55 (13), 4215-4219.
7. T. Zhang, et al., Adv. Energy Mater. 2016, 6 (3), 1501241.
8. T. Zhang, et al., Adv. Mater. 2015, 27 (47), 7824-7831.
(Invited) Local Electrolyte-Driven Redox Cycling within a Nanoporous Photoanode
Authors: Houle Frances A , Cheshire Thomas , Boodry Jeb 
Published: May 2020

Nanoporous photoanodes used in dye-sensitized solar energy conversion systems such as solar cells and solar hydrogen generators have been carefully studied to understand factors that influence their performance, as measured by photocurrents and open-circuit photovoltages. We have developed a chemically detailed, multiscale reaction-diffusion model that seeks to connect these observables to the detailed dye redox and electrolyte chemistry for the simpler dye-sensitized solar cell (DSC) system, incorporating dyes bound within a TiO2 nanoparticle-based anode, and an I-/I3
- redox shuttle connecting the anode to the cathode [1]. The model framework permits nanoscale characteristics of the interfacial and solution-phase redox processes, including charge trapping, to be connected to photocurrents and electron densities under various dye excitation scenarios, and is extendable to the more complex interactions occurring in hydrogen generators. In DSCs, it is generally assumed that the redox shuttle needs to make a full round trip between anode and cathode to convert I3
- to 3 I- at the cathode after dye reduction reactions in the anode. It is also thought that electron trapping by electrolyte components, in particular I2, is deleterious, and degrades performance. Detailed simulations assess these mechanistic elements. The results show that during operation, I- is deeply depleted in the photoanode pores, leading to significant populations of oxidized dyes and a shift in the I-/I3
- equilibrium with formation of I2. Electron trapping by I2, which forms I2
- at the photoanode-electrolyte interface, does not invariably affect photocurrent or photoanode charging. This is because the increased rate of I2
- disproportionation in the electrolyte enables local regeneration of I- within the pores and efficient dye reduction after photoexcitation, without requiring I3
- diffusion to the cathode. The possibility of local cycling, which results in photoanode redox activity without net current flow, has not been reported previously and suggest that causes of less-than-ideal performance may lie elsewhere. The simulations provide nanoscopic predictions for interfacial processes that control dye cycling. The timing of electrolyte anion diffusion toward the anode-dye interface within the pores, relative to charge injection and to dye neutralization, will be discussed.
[1] F. A. Houle, J. Phys. Chem. C 123, 14459-14467 (2019).
Controllable Vacancy Redistributions in Embedded Thin Films Under Concentrated Electric Fields
Authors: Nonnenmann Stephen S. 
Published: May 2020

The redistribution and accumulation of oxygen vacancies under electric field underpins both the functionality and degradation of electrical and electrochemical devices comprising oxide layers. Interfacial accumulations of oxygen vacancies form defect dipoles, significantly reduce the breakdown strength, increase the breakdown path area, yet facilitates charge transfer reactions. Confinement of both oxygen vacancy redistributions and their mobility remains critical to preserving function in oxide systems.
Here we study one of the most important, yet random transport processes: the redistribution of oxygen vacancies in binary oxides under high local electric fields. The ability to identify or predefine the shape, size, and location of vacancy distributions is critical to controlling interfacial properties of functional oxides. We achieved superior uniformity in HfO2 films by embedding highly-ordered metal nanoisland (NI) arrays to act as electric field concentrators. Embedded films exhibit significant reduction in operating voltages while displaying enhanced uniformity of resistance states. This behavior is attributed to the concentration of electric fields along Pt and Ti NIs and their interactions with the surrounding oxide film matrix environment, which induce separate and distinct filamentary formation mechanisms that affect the stability. A comparison of the density and distribution of the oxygen vacancies responsible driving filament dynamics is made via combined electrostatic force microscopy (EFM) and conductive atomic force microscopy (c-AFM) studies. Finally, the morphological evolution of conducting vacancy filaments is enabled by three-dimensional (3-D) c-AFM nanotomography and cross-sectional scanning transmission electron microscopy – energy dispersive spectroscopy (STEM-EDS) to provide direct correlations of nanoisland-oxide interactions with overall switching performance. The application of these exciting results to other vacancy-mediated electronic and electrochemical processes will also be discussed.
Mechanistic Understanding of OER Degradation of SOEC through Computational Modeling
Authors: Jin Xinfang , Huang Kevin 
Published: May 2020

One of the major barriers to the commercialization of solid oxide electrolysis cells (SOECs) for hydrogen production through electrochemical water splitting is the short cell/stack life caused by chemical-expansion-mismatch induced mechanical delamination of oxygen electrode. To address SOEC’s degradation problem, we have been developing an isostructural bilayer oxygen evolution reaction (OER) electrode that is electrocatalytically active and Cr-tolerant. The bilayer OER electrode structure consists of a commercial LSCF (La0.6Sr0.4Co0.4Fe0.6O3-
d)-GDC (Ce0.8Gd0.2O1.9 porous backbone on a thin SrCo0.9Ta0.1O3-
d (SCT10) film. The new oxygen electrode has an inherently fast OER electrokinetics (or high oxygen evolution rate) to mitigate the delamination problem by minimizing the accumulation of oxygen in OER electrode lattice and thus chemical stresses. To understand the fundamental Electro-Chemical-Mechanical coupling mechanism and its contribution to SOEC degradation, we propose a rigorous Multiphysics model to explore the interplays between reaction rates and transport properties in delamination probability of the pristine and bilayer OER electrodes.
Figure 1 shows a schematic of model domain to be constructed with details at the interface. The model will address how the dimensional change of oxygen lattice incurred in the electrode during OER-operation affects its bonding strength with the electrolyte and how electronic/ionic conductivity in the oxygen electrode as well as electrolyte will alter the change. We will apply classical charge transport conservation, Ohm’s law and multi-species Maxwell-Stefan’s equation to simulate electronic/ionic transport and gas diffusion in the porous electrode. The distribution of oxygen vacancy concentrations in the electrode and across the electrode/electrolyte interface will be considered a key descriptor for the chemically-induced lattice dimensional change. The displacement associated with the lattice dimensional change is governed by Navier’s equation. Different criteria will be used to evaluate the failure modes at the O2-electrode/electrolyte interface, such as elastic energy and Weibull approach. The research work will lead to a better understanding of the delamination mechanisms and effective mitigation plan, and provide guidelines to the experimental optimization of bilayer OER electrode processing with improved electrochemical and mechanical performance.
Figure 1 (a) Illustration of a SOEC cell; (b) Microscale electrode/electrolyte Interface Model; (c) Elastic energy in the particles and interfaces under chemical expansion.

Figure 1
Tailoring the Coefficient of Chemical Expansion in Perovskite Oxides through A Vs. B-Site Multivalent Cation Placement
Authors: Anderson Lawrence O , Perry Nicola H. 
Published: May 2020

Chemical expansion is a strain induced by a change in stoichiometry, such as oxygen loss. It can enable a material to actuate when exposed to different gas environments, and it can significantly impact device longevity when there are large concentration gradients across small material dimensions in multilayer devices. The desired magnitude of chemical expansion depends on the application; typically, the goal is a large expansion in the former and a small expansion in the latter, where compatibility with neighboring materials is of concern. Therefore, design rules for tailoring expansion from oxygen exchange are needed for the multitude of applications in which it is a contributing factor.
As oxygen leaves an oxide lattice during reduction, electrons are generated to preserve charge neutrality, which may move to multivalent cations; this process results in significant expansion of the multivalent cation, and the surrounding lattice, as the oxidation state of the multivalent cation decreases. Recently, an empirical formula describing the pseudo-cubic lattice constant of perovskite materials was developed [1], which relates the lattice parameter to the ionic radii of each cationic and anionic component. This equation predicts that changes in the B-site cation size will have a larger effect on the lattice parameter than an equal change at the A-site. If the multivalent cation is the only one changing size during redox processes, this equation suggests that its placement on the A or B site will have a significant effect on the magnitude of the overall lattice strain during oxygen loss or gain.
To test this theory, model perovskite bulk ceramic compositions with multivalent Pr(3+,4+) on the A site and on the B site were fabricated: PrGa0.9Mg0.1O2.95+
δ and BaPr0.9Y0.1O2.95-
δ, respectively. Strain values from dilatometry and defect concentrations from thermogravimetric analysis were used to calculate the coefficients of chemical expansion (CCE) in both materials, to determine the effect of multivalent cation placement. These measurements were performed under isothermal conditions while varying the pO2 to avoid effects from nonuniform thermal expansion at different stoichiometries. Multiple temperatures were analyzed to observe any temperature-related trends in CCEs and to determine any effects from crystal structure changes. The resulting CCEs will be interpreted not only in terms of multivalent A vs. B site placement but also considering other factors that may impact CCEs: crystallographic distortions, temperature, and charge localization.
[1] Marrocchelli, D., Perry, N. H., & Bishop, S. R. (2015). Understanding chemical expansion in perovskite-structured oxides. Physical Chemistry Chemical Physics, 17(15), 10028-10039.
Mechano-Electrochemistry – Towards Structural Batteries and Energy Harvesters
Authors: Muralidharan Nitin , Pint Cary L. 
Published: May 2020

Lithium ion batteries have revolutionized our modern society and have catalyzed the growth of advanced technologies such as electric vehicles and portable electronic devices. Batteries are dynamic mechano-electrochemical systems where the components and interfaces are subjected to significant mechanical stresses and strains during operation. Most current research approaches discard the coupled mechanical processes as an unavoidable byproduct. However, the coupling between mechanics and electrochemistry, mechano-electrochemical coupling, is a powerful yet unexplored tool. In this regard, our research efforts so far have been aimed at understanding and isolating this fundamental phenomenon followed by developing new classes of energy devices that leverage these findings for several unique applications. First, using principles of elastic strain engineering, we have demonstrated controllable modulation of electrochemical parameters governing energy storage systems as a function of applied strain. Next, building off these findings, we developed electrochemical-mechanical energy harvesters for harnessing ambient mechanical energy at very low frequencies (<5 Hz), a regime where the conventional state of the art piezoelectric and triboelectric energy harvesters have drastically reduced performances. The unique frequency tuning capabilities in this class of energy harvesters enable development of devices for use in human motion harvesting/sensing applications and multifunctional transient energy harvesting/storage devices. Additionally, to further understand the relationship between mechanical and electrochemical properties, we developed multifunctional structural supercapacitor and ultra-battery composites for use in load-bearing applications. Overall, our findings provide a broad framework for using mechano-electrochemistry as a design tool for developing next generation energy storage devices.
References:
[1] Energy harvesting devices and methods of making and use thereof. CL Pint, N Muralidharan - US Patent App. 16/058,046, 2019
[2] A Fully Transient Mechanical Energy Harvester. N Muralidharan, J Afolabi, K Share, M Li, CL Pint - Advanced Materials Technologies, 2018
[3] Mechano-Electrochemistry for Advanced Energy Storage and Harvesting Devices. N Muralidharan - 2018
[4] Ultralow Frequency Electrochemical–Mechanical Strain Energy Harvester Using 2D Black Phosphorus Nanosheets. N Muralidharan, M Li, RE Carter, N Galioto, CL Pint - ACS Energy Letters, 2017
(Invited) Intermediate Temperature Direct Ammonia Fuel Cell Using Alkaline Electrolyte System
Authors: Lattimer Judith , Patil Kailash , McCatty Steve , Mohan Yamini , Butler Katie , Xu Hui 
Published: May 2020

Ammonia is a very attractive carbon-neutral fuel due to its low cost, high energy density, and existing transportation infrastructure. However, the viable commercial application of direct ammonia fuel cells (DAFC) has not been realized, largely due to materials challenges. Generally, DAFCs either use low temperature polymer electrolytes, which are limited by low reaction rates, or use high temperature solid oxide electrolytes, which suffer from severe material thermal degradation. We have developed an intermediate temperature alkaline electrolyte-based DAFC that operates at 400-600 °C, enabling high reaction rates while limiting thermal degradation. This DAFC is based on our innovative molten hydroxide electrolyte impregnated in a porous ceramic matrix, which has conductivity as high as 0.4 S/cm at 350 °C, enabling rapid hydroxide transport. The DAFCs use state-of-the-art ammonia oxidation catalysts and ammonia-tolerant ORR catalysts developed in-house and by our collaborators at SUNY Buffalo and University of Delaware. Our DAFC has demonstrated an OCV of 1.2 V and can achieve 300 mA/cm2 at 0.86 V, or >250 mW/cm2 power from pure humidified ammonia. It is stable for days without loss of activity and has very low ammonia crossover, enabling the high OCV and high power density without catalyst poisoning. Further work on catalyst development and cell design is underway to achieve higher power densities and reduce PGM catalyst loading and operation temperature, making this a more commercially viable technology.
Acknowledgements: This work is financially supported by the Department of Energy’s ARPA-E under the award# DE_AR000814
(Invited) Two Phase Flow in Porous Transport Layer Structures in Polymer Electrolyte Water Electrolysis
Authors: De Angelis Salvatore , Schuler Tobias , Schmidt Thomas J. , Büchi Felix N. 
Published: May 2020

In polymer electrolyte water electrolysis (PEWE), mass transport losses are the least understood overvoltage contribution. Underlying origin as well as correlation parameters with the micro-structure of the porous transport layer (PTL) are not identified. X-ray imaging has the potential to clarify the relation between oxygen transport and mass transport losses, but in the highly absorbing titanium porous structures the contrast between water and gas is weak. Therefore, imaging parameters need to be carefully tuned to identify the two phases.
Using synchrotron light, X-ray tomographic microscopy was applied to study ex-situ and operando PEWE cells and the two-phase flow in the PTL (see image and rendering in Figure 1) and at the interface1,2 to the catalyst layer was observed. The combination of electrochemical characterization with X-ray imaging leads to better understanding of the controlling parameters and the related mass transport losses.
References
1. T. Schuler, R. De Bruycker, T.J. Schmidt and F.N. Büchi, Journal of The Electrochemical Society, 2019, 166, F270-F281.
2. T. Schuler, J.M. Ciccone, B. Krentscher, F. Marone, C. Peter, T.J. Schmidt and F.N. Büchi, Advanced
Energy Materials, 2019, 1903216

Figure 1
Anodic Oxidation of Bisamides
Authors: Becker James Y. 
Published: May 2020

Previously [1] we studied the anodic oxidation of bisamides of type RCONH(CH2)nNHCOR (n = 2-4) under controlled current electrolysis (CCE), in methanol. Those with 3 and 4 methylene groups undergo mostly mono- and dimethoxylation at the alpha-position to 'N' atom. However, when the spacer contains two methylene groups only the anodic process favor fragmentation products due to CH2-CH2 bond cleavage, as shown in Eq. 1.
Following the above results, the anodic oxidation of aromatic bisamides with ‘CH2CH2’ as a spacer (ArCONHCH2CH2NHCOAr), has been investigated [2] in acetonitrile, and under controlled potential electrolysis. The outcome indicates that the major products involve unsymmetrical geminal bisamides (Eq. 2) that are difficult to synthesize by other methods.
References
[1] T. Golub and J.Y. Becker, Beilstein J. Org. Chem.
2018,
14, 861–868.
[2] T. Golub, G.-Y. Dou, C.-C. Zeng and J. Y. Becker, Org. Lett., 2019, 21,
7961-7964 [DOI: 10.1021/acs.orglett.9b02917].

Figure 1
Electrochemical Total Synthesis of Pratosine By Controlling for the Anodically Initiated One-/Two-Electron Transfer Process
Authors: Okamoto Kazuhiro , Chiba Kazuhiro 
Published: May 2020

Pratosine is a type of a pyrrolophenanthridone alkaloid that includes indole ring and electron donating group-substituted N-benzoyl moiety. Many researchers demonstrated various synthetic reactions to access a simple poly-heterocyclic structure of pyrrolophenanthridone. For instance, intramolecular cyclization between indoline and N-benzoyl moiety was accomplished by stoichiometric Pd-mediated C-H activation1, hypervalent iodine mediated oxidative cross-coupling2 and inverse electron-demand Diels-Alder reaction3. Continuously DDQ oxidation to convert indoline to indole is necessary in all case.
We established electrochemical intramolecular radical cation cross-coupling and indole synthesis reaction. These reaction was initiated by same anodic oxidation for electron-rich benzoyl group, but acid or base additive-dependent different electron-transfer pathway was occurred in both cyclization and indole ring forming reaction.
Reference
(1) DC. Black, PA. Keller, N. Kumar, Tetrahedron Lett.
1989, 30, 5807-5808.
(2) MD. Ganton, MA. Kerr, Org. Lett.
2005, 7, 4777-4779.
(3) DL. Boger, SE. Wolkenberg, J. Org. Chem.
2000, 65, 9120-9124.

Figure 1
Efficient and Selective Aryl-Nitro Reduction of Pharmaceutical Intermediates
Authors: Graaf Matthew D. 
Published: May 2020

Hydrogenation of nitro groups to produce anilines is a well-established transformation in organic chemistry and the pharmaceutical industry [1]. However, high pressure hydrogenations can be hazardous at multi-kilo scales and functional group compatibly is often problematic for pharmaceutical intermediates requiring a specialized catalyst [2]. In a continued effort to promote electrochemistry in pharma as a greener and safer alternative, an improved method of electrochemically producing anilines has been achieved. In this presentation, the development of a robust and efficient undivided Aryl-nitro reduction will be discussed.
References:
[1]: Jones, W.; Platinum Metals Rev., 1958, 2, 86
[2]: Blaser, H-U., Steiner, H., Studer, M.; ChemCatChem., 2009, 1, 210

Figure 1