bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Understanding Charge Separation in Semiconductor for Efficient Photoelectrochemical Water Splitting
Authors: Hwang Yun Jeong , Chae Sang Youn , Min Byoung Koun 
Published: February 2020

To mitigate the global warming issue caused by the current heavy dependence on fossil fuels, the researchers propose hydrogen as an alternative energy carrier, which can be produced from water splitting in a photoelectrochemical (PEC) cell. In the PEC cell, sunlight can be absorbed and stored in the form of chemical energy (i.e. hydrogen) by using a semiconductor photoelectrode. To achieve an efficient photocatalytic electrode, the semiconductor material has to satisfy several requirements such as high visible-light absorbing ability, effective charge separation, and fast catalytic reaction on its surface. However, a single semiconductor material often fails to have poor overall efficiency. Therefore, combination of two or more semiconductor junctions are suggested to compensate the other material’s drawbacks.
For example, WO3/BiVO4 heterojunction is one of the successful combinations in which WO3 play a role in electron transfer and BiVO4 increases the visible light absorption to increase the photoanodic water splitting performance. The charge separation properties at the WO3 and BiVO4 interface are characterized by measuring the photocurrent in the absence/presence of hole scavengers, light absorption spectroscopy, and intensity-modulated photocurrent spectroscopy (IMPS). The morphology and the thickness of the mesoporous WO3 layer were controlled to monitor to understand the charge separation efficiency at the interface. Our study can provide insights to heterojunction design.
Meanwhile, a p-type chalcopyrite Cu(In,Ga)(Se,S)2 (CIGS) semiconductor was prepared by a solution precursor processed method and used as a photocathode for hydrogen evolution reaction, and charge separation properties on its surface was studied by electrochemical impedance spectroscopy measurement. By controlling the surface states and introducing the passivation layer of ZnS, the photocurrent with the CIGS thin film on the transparent FTO substrate was significantly improved. Also, CIGS on FTO substrates was useful to compare PEC performances under forward and backward illumination conditions. Since slow electron transfer in CIGS photocathode is believed to limit PEC performance, further decrease of the defect structure of CIGS film is desirable for efficient solar-to-hydrogen conversion.
Highly Aligned Oxide Nanotubes: Engineering Reactive Centers for Photocatalysis
Authors: Schmuki Patrik , Zhou Xuemei , Liu Ning , Altomare Marco 
Published: February 2020

TiO2 nanomaterials have over the last 30 years attracted tremendous scientific and technological interest. Particularly various 1D and highly defined TiO2 morphologies were explored for the replacement of nanoparticle networks and were found in many cases far superior to nanoparticles or their assemblies. Nanotubes or wires can be grown by hydrothermal or template methods, or even more elegantly, by self-organizing anodic oxidation. The latter is not limited to TiO2 but to a full range of other functional oxide structures on various metals and alloys can be formed. These advanced and doped morphologies can be grown on conductive substrates as ordered layers and therefore can be directly used as functional electrodes (e.g. photo-anodes). The presentation will focus on these highly ordered nanotube arrays of TiO2 (and similar) and discuss most recent progress in synthesis, modification and applications towards photocatalytic and photoelectrochemical applications such as noble-metal-free H2 generation or the site-selective placement of active centers onto/into these tube layers.
Literature:
- P. Roy, S. Berger, P. Schmuki, Angew. Chem. Int. Ed. (2011), 2904
- K. Lee, A. Mazare, P. Schmuki, CHEMICAL REVIEWS, 114 (2014) 9385
- N. Liu, P. Schmuki et.al. Nano Letters, 14 (2014) 3309
- N. Liu, P. Schmuki et.al. Angew. Chem. Int. Ed. 53 (2014) 14201
- X. Zhou, N.Liu, P.Schmuki ACS Catal., ,7 (2017) 3210
Enhanced Electrochemical Ammonia Production Via Peptide-Bound Metals and Effects on the Hydrogen Evolution Reaction
Authors: Loney Charles , Suttmiller David , Acharya Prashant , Maheshwari Sharad , Wiles Luke , Ayers Katherine E , Gellett Wayne L. , Janik Michael John , Greenlee Lauren F , Renner Julie N. 
Published: February 2020

Approximately half of the people on the planet are alive due to synthetically produced ammonia. However, due to the fossil fuels used in the current process, ammonia production contributes a significant amount to the world’s greenhouse gas emissions. By taking an electrochemically-based approach to this process, those emissions can be eliminated. However, current catalysts are not selective for the desired reaction. We hypothesize that 3D surface modifications can be utilized to overcome these limitations and create catalysts which mimic the selectivity of the nitrogenase enzyme, an enzyme that catalyzes the reduction of nitrogen to ammonia at mild temperatures and pressures. Therefore, in this study, peptide sequences have been designed to mimic the general function of the naturally-occurring nitrogenase enzyme. Recent results in an alkaline, solid-state electrochemical cell show promise using a synthetic peptide bound to iron(iii) oxide nanoparticles, which yield an electrochemical ammonia production rate that is 10x higher than the catalyst without bound peptide. Preliminary, repeated experiments in a liquid electrolyte cell at room temperature and atmospheric pressure illustrate similar promising results. Furthermore, gas adsorption isotherms suggest that this peptide does not significantly block nitrogen adsorption, and that the catalysts maintain the same surface area after binding to the peptides.
In addition, a simple and tunable peptide system has been designed to better understand how peptides influence electrochemical reactions. Emphasis is placed on understanding the hydrogen evolution reaction (HER) on Au, Fe2O3, and Pt metal surfaces, as HER is the main competing reaction for ammonia production. One of our main tools used to understand these peptide effects is a quartz crystal microbalance with dissipation (QCM-D), which is utilized in combination with an electrochemistry module (QEM) and humidity module to give real-time electrochemical and surface information. Importantly, the QCM-D is sensitive enough to measure the mass loading of the peptide on metal surfaces. Furthermore, the humidity module allows us to study the peptides’ effects on water uptake, which will also be useful for understanding HER in a basic environment, as water is the proton source. For instance, preliminary results show that at least one tripeptide species has a significant hydrophilic effect on water uptake when used on an Au sensor. Overall, these data are anticipated to influence general guidelines when designing selective catalysts for electrochemical reactions.
Post-Functionalization of P3HT Via Anodic Oxidation with High Current Efficiency
Authors: Kurioka Tomoyuki , Nishiyama Hiroki , Tomita Ikuyoshi , Inagi Shinsuke 
Published: February 2020

Recently, post-functionalization has attracted attention as a useful strategy to obtain functional polymers. We have already reported the anodic chlorination of poly(3-hexylthiophene) (P3HT) in the presence of chloride ions under a constant potential condition, and found that introduction of a chlorine atom to the 4-position of the thiophene rings could tune the optoelectronic properties of P3HT. However, the current efficiency of this reaction was low because of the competitive oxidation between P3HT and the chloride ions used as a chlorine source.1

In this study, we improved the current efficiency of the anodic chlorination of P3HT by using boron trifluoride-diethyl ether complex (BFEE). BFEE is well-known to decrease oxidation potentials of aromatic compounds due to the π-complex formation between BF3 and aromatic rings.2 BFEE used as a solvent and an electrolyte in voltammetric studies successfully decreased the oxidation potential of P3HT, and increased the oxidation potential of chloride ions. These interesting effects of BFEE also worked in the macroscale electrolysis of P3HT, giving higher current efficiency compared to the conventional methods.
References

S. Hayashi, S. Inagi, K. Hosaka, T. Fuchigami, Synth. Met., 2009, 159, 1792.

S. Jin, G. Xue, Macromolecules, 1997, 30, 5753.

Figure 1
Anodic Thiocyanation of Alkenes in Formic Acid
Authors: Becker James Y. , Gitkis Anna 
Published: February 2020

Previously we studied the anodic thiocyanation of aromatic compounds [1, 2] followed by a one-pot anodic thiocyanation and isothiocyanation of alkenes in both acidic two-phase (water-dichloromethane) and homogeneous one-phase (water-acetonitrile) media [3]. The present talk will describe a two-step thiocyanation of alkenes in formic acid [4] and a plausible mechanism for this reaction.
At the bottom there is a typical example showing the type of a major product obtained in this process.

References
[1] A. Gitkis, J.Y. Becker, J. Electroanal. Chem., 593 (2006) 29-33.
[2] A. Gitkis, J.Y. Becker, Electrochim. Acta, 55 (2010) 5854-5859.
[3] A. Levy, J.Y. Becker, Electrochim. Acta, 178 (2015) 294–302.
[4] A. Gitkis, J.Y. Becker, Electroanalysis, 28 (2016) 2802-2807.

Figure 1
Controlled Interactions between Engineered Proteins and Acidic Polymer Electrolytes
Authors: Su Zihang , Waston Skylar T. , Renner Julie N. 
Published: February 2020

Bio-electrochemical technologies have an important and growing role in healthcare, with applications in sensing and diagnostics, as well as the potential to be used as implantable power sources and be integrated with automated drug delivery systems. Enzymatic bio-electrodes are especially attractive because they are biocompatible, highly selective, and efficient catalysts at physiological conditions. Challenges associated with enzyme-based electrodes include low current density and short functional lifetimes. An important aspect in creating efficient electrochemical devices is facilitating proton transfer in electrode layers. Often solid polymer electrolytes (ionomers) are utilized in industrial devices such as fuel cells and electrolyzers, but these polymers need to be carefully controlled in bio-electrochemical environments, such that they do not denature enzymes.
Protein engineering is emerging as a powerful tool to overcome the challenges in manufacturing enzyme-based electrodes. By taking advantage of the ability to precisely define protein sequences, electrodes can be organized into high performing structures. While many protein engineering tools have been developed for bio-electrodes, no proteins have been specifically designed to help organize ionomer on conductive surfaces. We propose to utilize highly tunable and easily manufactured structural protein sequences found in nature to control the placement of these ionomers, thus potentially enable their use in a multitude of devices.
In this talk, we will discuss the protein design, binding and aggregation behavior with ionomer, the effect of ionomer on protein secondary structure, and surface analysis of samples. Specifically, mass change data from a quartz crystal microbalance with dissipation (QCM-D) and hydrodynamic radii data gathered using dynamic light scattering (DLS) show proteins can be modified to bind with ionomer (Nafion®), and this interaction happens in solution as well as when the proteins are immobilized on metal surfaces. Circular dichroism (CD) data shows the secondary structures of the proteins in the presence on ionomer remain unchanged. Surface analysis is performed using x-ray photoelectron spectroscopy (XPS) and an atomic force microscope (AFM) and corroborate the binding analysis results. Since the purpose of these composite materials is to facilitate proton transfer, conductivity through thin films is also characterized. Overall, this work shows for the first time that protein sequences could serve as a promising tool in controlling ionomer architecture. This discovery has broad applications in bio-electrodes, but can also be used to understand the impact of ionomer organization on fuel cell and electrolysis membrane electrode assemblies as well.
Electron Transfer Processes Enabling Genotoxicity Sensor Arrays
Authors: Rusling James F 
Published: February 2020

Design of biosensor arrays for drug development and diagnostic applications has become a major activity in bioelectrochemistry. Achieving efficient electron transfer processes to produce reliable, reproducible, and sensitive output signals is a critical goal for such devices. This paper describes key electron transfer processes in our development of sensors for the chemistry of genotoxicity, defined here as resulting from the damage and oxidation of DNA by chemicals and their metabolites. This research is driven mainly by the need to screen for the potential genotoxicity of new drug and environmental chemical candidates, about 30% of which have toxicity issues that do not manifest until human clinical trials. A major issue is metabolic chemistry driven mainly by cytochrome (cyt) P450s and other enzymes, and we needed to produce metabolites in our arrays. Metabolic chemistry involves electron-transfer catalysis of organic reactions, usually involving oxygen transfer in the case of cyt P450s. We have found ways to efficiently transfer electrons into cyt P450s in thin films via their natural reductase electron-transfer partners to catalyze metabolic reactions electrochemically via mechanisms that are the same as in our livers and other organs. Optimizing the electrode-driven electron transfer chain from electrode to reductase to cyt P450 has allowed us to replace expensive NADPH as reducing agent and simplify our genotoxicity arrays.
We also needed a way to detect the resulting metabolite-related DNA damage in sensors combining thin LbL films of metabolic enzymes and DNA in which the metabolites are generated and react with DNA. We found that guanines in DNA chains can react in an electrocatalytic process involving electron transfer to a Ru or Os metallopolymer (RuPVP) to output visible light via electrochemiluminescence (ECL). A complex electron transfer sequence drives an electrocatalytic process that oxidizes RuII to RuIII to oxidize guanine moieties in the DNA and produces visible light. The OsII/OsIII redox couple can be used in a similar ways to design sensor arrays selective for DNA oxidation.
Electrocatalytic Cyt P450 oxidations, ECL generation and microfluidics are combined in our most sophisticated genotoxicity sensor arrays. When DNA is adducted by metabolites, its double-stranded structure is disrupted and RuIII sites in the film gain better access to guanine moieties to produce more ECL light. The primary oxidation product in DNA oxidation is 8-oxo-guanine, which in a second step is selectively oxidized by OsIII complexes to give ECL at a lower applied potential that for RuIII/RuII. Examples of metabolite-related DNA damage and oxidation, including the genotoxic potential of e-cigarettes, will be discussed.
THz SERS Observation of Benzenethiol Monolayers on Electrode Surfaces
Authors: Ikeda Katsuyoshi 
Published: February 2020

Surface-selective vibrational spectroscopy is a powerful tool to study various interfacial phenomena such as electrochemical reactions at electrode/electrolyte interfaces. Among various spectroscopic methods, surface enhanced Raman scattering (SERS) is a promising method to conduct in-situ observation in IR- and THz-opaque media. According to recent technological advancements in fabrication of optical filters, elimination of Rayleigh scattering has become highly efficient. Thus, it is now expected that very low-frequency vibrations such as THz vibrations can be observed even in aqueous solutions [1]. Figure shows that an extramolecular vibration of benzenethiol monolayers with ultra-low frequency is indeed observable using this method. We will discuss charge transfer resonances at metal/molecule interfaces based on this low frequency vibration.
Figure caption
THz-SERS spectra of monolayers of benzenethiol derivatives on a roughened Au substrate
Reference
[1] M Inagaki, K. Motobayashi, K. Ikeda, J. Phys. Chem. Lett., 8, 2017, pp. 4236-4240.

Figure 1
Detection of Reactive Oxygen Species in AEM Fuel Cells Using in Situ Fluorescence Spectroscopy
Authors: Zhang Yunzhu , Parrondo Javier , Sankarasubramanian Shrihari , Ramani Vijay 
Published: February 2020

Anion exchange membrane (AEM) stability is a long-standing challenge that has limited the widespread development and adoption of AEM fuel cells. It is essential to understand the mechanism of AEM degradation during fuel cell operation. There are multiple modes of AEM degradation, broadly classified as chemical, mechanical and thermal degradation. Chemical degradation is among the most destructive modes, and can be further sub-divided into nucleophilic degradation (induced by the hydroxide ion), and oxidative degradation (induced by reactive oxygen species). While the former has been extensively studied, there has been minimal work on oxidative AEM degradation.
The reactive oxygen species produced during the operation of an AEM fuel cell have hitherto not been detected during operation. Given the high pH, it is postulated that superoxide anion radicals (O2
⋅-), as opposed to hydroxyl radicals, are primarily involved in the degradation progress. The objective of this study was to confirm O2
⋅- formation during AEM fuel cell operation and to monitor in real-time the rate of O2
⋅- generation in an operating fuel cell using in situ fluorescence spectroscopy.
1,3-diphenlisobenzofuran (DPBF) was chosen as the fluorescence probe, the sensitivity of which towards O2
⋅- was evaluated by performing ex situ experiments in a semi-batch reactor. We demonstrate that the fluorescence intensity of this dye selectively decreased upon exposure O2
⋅-. DPBF was then incorporated into an AEM (membrane was solution cast after mixing the dye with the casting solution), which was assembled into a fuel cell. O2
⋅-
generation in an operating AEM fuel cell was then monitored via in situ fluorescence spectroscopy using a bifurcated optical fiber probe, when the cell was operated in H2/O2 mode. To confirm the impact of O2
⋅- on AEM degradation, independent experiments (without dye) were performed under identical conditions, under both H2/O2 and N2/N2 modes, and the ionic conductivity and ion exchange capacity were monitored to estimate degradation extent based purely on nucleophilic degradation. From our in situ fluorescence studies, we were able to independently estimate the rate constants and activation energy for oxidative AEM degradation in an operating AEM fuel cell.
Characterization of the Electrochemical Detection of NG-Hydroxy-L-Arginine
Authors: Arral Mariah Lynn , Halpern Jeffrey Mark 
Published: February 2020

NG-Hydroxy-L-arginine (NOHA) is a suspected biomarker in breast cancer due to its involvement in the L-arginine metabolism [1]. Previous research in human breast cancer cells has shown that NOHA, a potent arginase inhibitor, has an antiproliferative and apoptotic actions on the arginase-expressing cells [1]. NOHA is a stable intermediate product in the production of NO from the consumption of L-arginine [1]. L-ornithine and L-citrulline are also involved in the metabolism of L-arginine through the urea cycle; the urea cycle has been known to be disrupted in cancer patients [1]. Early detection of cancer is important for rapid treatment options to be available [2]. Electrochemical detection is an established, cost-effective method that has potential to detect the onset of cancer because of its ability to successfully detect low levels of analyte concentrations. Before a robust biosensor sensor can be made the characterization of the electrochemical detection of NOHA needs to be done.
Electrochemical activity of NOHA was investigated with cyclic voltammetry and differential pulse voltammetry. NOHA was found to have an oxidation and reduction peak at 355 mV and 188 mV vs. Ag/AgCl respectively. In cyclic voltammetric measurements a scan rate of 50 mVs-1 was used over the applied potential of -0.2 to 0.6 V vs Ag/AgCl. Triplicate data was obtained for serial dilutions of NOHA in two different buffers; Phosphate Buffer Saline solution pH 7.3 (PBS) and 100uM L-Ornithine, 10uM L-Citrulline, and 100uM L-Arginine in PBS (LOCA). The electrochemical detection of NOHA in a LOCA solution was done to understand the effect of a urea cycle metabolite mixture on electrode fowling and sensitivity. A shift in oxidation peak voltage was found for the LOCA solution by 5 mV to 360 mV. The sensitivity of the NOHA in PBS and LOCA solutions were found to be 5.4 nA/uM and 4.8 nA/uM respectively. In addition to our multiple data points to discuss sensitivity and reproducibility in the detection of NOHA, we will report kinetic information including the number of electrons transferred and diffusivity. We will also discuss our progress to decrease the limit-of-detection of NOHA in an effort to make a more sensitive bioanalyte sensor.
[1] R. Singh, S. Pervin, A. Karimi, S. Cederbaum, and G. Chaudhuri, “Arginase activity in human breast cancer cell lines: Nω-hydroxy-L-arginine selectively inhibits cell proliferation and induces apoptosis in MDA-MB-468 cells,” Cancer Res., vol. 60, pp. 3305–3312, (2000)
[2] Zhen Zhang, Robert C. Bast, Jr., Yinhua Yu, Jinong Li, Lori J. Sokoll, Alex J. Rai, Jason M. Rosenzweig, Bonnie Cameron, Young Y. Wang, Xiao-Ying Meng, Andrew Berchuck, Carolien van Haaften-Day, and Neville F. Hacker, Henk W. A. de Bruijn, Ate G. J. van der Zee, Ian J. Jacobs, Eric T. Fung, and D. W. Chan, “Three Biomarkers Identified from Serum Proteomic Analysis for the Detection of Early Stage Ovarian Cancer,” Cancer Res., vol. 64, pp. 5882–5890, (2004)
Photorechargeable Lithium-Ion Battery Electrode Based on Nanocrystals of Anatase TiO2 Combining Energy Conversion and Storage
Authors: Bouteau Gaspard , Sagaidak Iryna , Andriamiadamanana Christian , Nguyen Van Nhien Albert , Sauvage Frédéric 
Published: February 2020

The intermittent nature of renewable energies, in particular solar, limits its utilization at demand. Its hybridization with an energy storage reservoir is required, such as an electrochemical battery, to accommodate the balance between grid delivery and consumer demand. Although photovoltaic and batteries are two mature technologies widespread, their combination require electronics management, good assessment on both power dimensioning and ageing of each component, and still require a substantial cost reduction to become competitive with fossil fuels and nuclear.
With long term view, the approach of bridging together the functions of solar conversion and its storage at the molecular level is worth attention for both scientific and technological point of view to pave the way towards photo-rechargeable ion batteries or non-intermittent photovoltaic displays.
Tributsch in the early 80’s demonstrated the possibility to trigger light-induced interfacial ion transfer in mixed electronic/ionic semi-conductors as a result from the charge separation process within the depletion region (1). Up to now, the charges stored in such materials are only confined to the extreme surface (energy density less than 1 Wh/Kg), limited by the Debye length of the space charge layer (2). In this presentation, we will expose our strategy based on anatase TiO2 nanocrystals of 4 nm size assembled in carbon-free electrode to overcome this limitation. Anatase TiO2 with its n-type semi-conducting properties affords the de-insertion of lithium ions under illumination to counterbalance the hole transfer to Ti3+ induced by light. As a result from downsizing to such a nanoscale, surface reactions are promoted with respect to the total volume of particles. Consequently, our results, which will be discussed in-depth, show the possibility to quantitatively photorecharge an electrode of ca. 700 µAh/cm2 capacity in about one hour light exposure (Fig. 1). Both the mechanism and electrode performances will be discussed during this communication.

Figure 1