bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Electrochemical, Photoelectrochemcal and Photocatalytic Abatement of Emerging Pollutant
Authors: Hussain Sajjad 
Published: February 2020

Drug residues are unregulated emerging pollutants and are frequently found in the aquatic environment. Due to their extensive use, presence in the aquatic environment and their potential for impacts on wildlife and humans, it is becoming an important environmental issue. The present study evaluates the photo-assisted electrochemical treatment of sulfamethoxazole (SMX), an antibiotic used in the prevention and treatment of human and animal diseases. The experiments were carried out in a photo illuminated flow cell reactor and the effects of current density (10-60 mA cm-1) and concentration of sodium chloride in the supporting electrolyte were determined. The Drug could be removed completely at all current densities while TOC abatement was appreciable during the process. The process followed pseudo-first order kinetics and values of electrical energy-per-order were dependent on current density and sodium chloride concentration. Different reaction intermediates were separated and identified by liquid chromatography coupled with mass spectrometry (LC-MS), thereby providing an insight into the mechanistic details of the degradation pathway. The photo-assisted electrochemical degradation proceeded through competitive reactions such as chlorination, hydroxylation and substitution on the aromatic ring, while further ring opening gave rise to more simple organic compounds and, ultimately, the mineralization of SMX. The possible degradation route were also proposed and discussed. . The efficiency of photoelectrochemical process was compared with photo-catalytic and electrochemical separately, and showed a synergism for TOC removal.
A Simple Flow Cell for the Measurement of Groundwater Arsenic(3+/5+) in the Field
Authors: Mays Douglas , Hussam Abul 
Published: February 2020

The focus of this methodology is to use high performance automated square-wave anodic stripping voltammetry (HPSWASV - A technique where the background is subtracted dynamically in a square wave format while anodic stripping voltammetry is being recorded with two current sampling on the pulse. We have built the potentiostat and wrote the code to perform this technique specifically suitable for arsenic measurement on a gold microwire electrode.) as the technique in a system that is field deployable with a 2-electrode cell (a working and a reference electrode). The counter electrode, often made of platinum and can be one of the most expensive components is not needed in this system given the small current generated during the electroanalytical process. This methodology is perfectly suitable with microelectrodes with low current demand. It is inexpensive, simple and easy to fabricate anywhere or produced commercially. The cells can last for hundreds of measurements with novel in-situ pulsed cleaning. The estimated total cost with dedicated potentiostat, cell, and laptop computer is approximately 1000 USD. This a one-time cost.
The specifics of the electrochemistry are as follows: using anodic stripping voltammetry with reagent grade hydrochloric Acid (HCl) and 100 s deposition time. This deposition time shows the best results without any data exclusion. The preconditioning procedure employed was cyclic voltammetric (CV) from 0.0 to 1.5 V at a scan rate of 100 mV/sec in 0.5 M H2SO4. Oxidation and reduction peak potentials were examined closely. In the analysis of 200+ CV runs, the average oxidation and reduction peak potentials were 1.284 ± 0.01 V and 0.849 ± 0.005 V respectively. These values are within 10 – 15% of those potentials cited in the literature. The calculated surface areas were 0.0607 ± 0.0054 cm2 and 0.0095 ± 0.0030 cm2 for oxidation and reduction respectively. The average oxidation surface area was larger than the reduction and might be explained by differing oxidation states of clusters of Au atoms on the surface not being reduced or not in close enough proximity to the surface for reduction. A solid gold wire electrode, which requires no separate gold deposition, is much more acceptable when in the field.
Results from my prototype systems measure between 10 -100 ppb As(III) with good repeatability. As(V) is measured by first scanning for As(V) which comes off at a higher potential than As(III) and then determining the concentration using the method of standard addition. The As(V) in the sample solution is then reduced to As(III) and the sample solution is scanned again for As(III) and a standard addition conducted. The difference between the two (2) unknown sample concentrations is the quantitation of As(V).

Figure 1
Special Active Pt(100) Site for Room Temperature Electrochemical Activation of Methane
Authors: Ma Hai-bin , Sheng Tian , Zhou Zhi-You , Sun Shi-Gang 
Published: February 2020

Methane is the main component of natural gas and a byproduct of oil refining and chemical processing. Due to its inertness, high temperature and high pressure are required for the most popular way of converting methane. Electrochemical conversion of methane has been put a lot of interests due to its facile control of selectivity by monitor electrode potential and its relatively mild working conditions. Although many studies have been conducted to improve methane conversion rate and selectivity based on solid oxide fuel cells, the basic methane electrooxidation mechanism remians poorly understood. Single crystal electrode with defined atomic arrangement proves to be a good model for the study of surface reaction mechanism.
In this study, the interaction between methane and well-defined Pt single crystal surfaces at room temperature was studied by electrochemical method and in situ FTIR spectroscopy. The results demonstrated that, amongst the three basal planes of Pt single crystal (Pt(111), Pt(110), Pt(100)), only Pt(100) can activate methane, in which the dissociation of methane could be detected at potentials above 0.0 V (vs.SCE) (Fig.1). At potential range between 0.0 V and 0.15 V, methane may be mainly dehydrogenated to produce spices like CO/COH, resulting in the decrease of Hudp on Pt(100). At potentials above 0.15 V, such spices can be further oxidized to form CO2. In situ FTIR spectroscopy studies indicated that methane can be oxidized to CO on Pt(100) surface and the CO mainly bound to hollow sites, moreover no oxidation product was detected on Pt(111) and Pt(110). DFT calculations show that on Pt(111) and Pt(100), the most stable surface species both are CH*, while on Pt(100) the most stable one is CH2*. On Pt(100), CH* prefers to be oxidized by O* with the lowest barrier being 0.4 eV. However, on Pt(110) and Pt(111), CHx* oxidation is much more difficult since the coupling between the carbon species and OH* is as high as 1.03 eV and 0.85 eV, respectively.
This study revealed the surface structure-reactivity in methane activation on platinum catalyst, and will give more insight into the design and synthesis of electrocatalyst for methane conversion.

Figure 1
Hydrogen and Nitrogen Modification of Anodized TiO2 Nanotube Arrays for Photoelectrochemical Oxidation of Water
Authors: Xu Yin , Zangari Giovanni 
Published: February 2020

TiO2 nanotube arrays (NTs) made by electrochemical anodization exhibit significant potential as a photoanode in low cost, sustainable photoelectrochemical cells for solar water oxidation.1 The wide bandgap (3.2eV, λ < 387 nm) of these materials, however, limits the photocurrent, and the low mean free path of charge carriers further limits performance. Formation of substoichiometric phases or generation of suitable defects have been proven to enhance photoresponse.2 Thermal treatment of TiO2 under reducing atmosphere, for example, generates high-conductivity, oxygen deficient TiO2-xmaterials, including the Magneli phases. Similarly, nitrogen doping may decreases the band gap, enabling increased light absorption.
In this work, anodized TiO2 nanotubes were modified via hydrogen or ammonia gas treatments to generate various substoichiometric phases, characterized by reduced bandgap and higher conductivity. In particular, annealing in partial hydrogen pressure (5 at%) leads to a gradual phase transformation of anatase to rutile and various Magneli phases, yielding an enhanced photoelectrochemical response up to 2.2-fold at 1.23VRHE. Annealing in ammonia and argon flow on the other hand results in oxygen loss with barely detectable N incorporation, resulting in a 4-5 fold photocurrent enhancement at 1.23VRHE with a significant cathodic shift (~100 mV) of the onset potential. The fraction of the photogenerated charges utilized for water splitting was estimated by comparing photoelectrochemical performance with or without hole scavenger species.3 All modified samples displayed higher water oxidation efficiency (above 80%) compared with unmodified TiO2(~65%). In order to evaluate the surface disorder introduced by the modification, electrochemical impedance spectroscopy (EIS) was carried out, showing higher charge carrier density. Overall, this work demonstrates that hydrogen or ammonia annealing treatments enhance significantly photoelectrochemical performance.

References:

1. L. Tsui and G. Zangari, J. Electrochem. Soc. , 161, D3066–D3077 (2014)
2. X. Chen, L. Liu, and F. Huang, Chem. Soc. Rev., 44, 1861–1885 (2015)
3. L. Tsui, Y. Xu, D. Dawidowski, D. Cafiso, and G. Zangari, J. Mater. Chem. A, 4, 19070–19077 (2016).

Figure 1. Photochemical response of hydrogen reduced TiO2 (a) and nitrogen modified TiO2 (b).

Figure 1
Solar Photoelectrochemical Water Purification
Authors: Cruse Ryan , Sullivan Michael John , Smotkin Eugene S. 
Published: February 2020

Bipolar electrodes based on titanium dioxide are configured for water purification. The TiO­2 photo-anode oxidizes organic pollutants. Concomitant with photooxidation, oxygen is reduced at the dark cathode to yield hydrogen peroxide which serves as a bio-disinfectant. The device uses a very low cost semiconductor material (titanium dioxide with no sensitizer) and requires only low technology fabrication methods. The photoanode is prepared by arc-anodization of titanium foil. The dark cathode is prepared from hydrophilic carbon gas diffusion material typically used in fuel cells. The cell design and bio-disinfectant efficiency will be discussed.
Effects of Nanoscale Interfacial Design on Photocatalytic Hydrogen Generation Activity at Plasmonic Au–TiO2 and Au–TiO2/Pt Aerogels
Authors: Pietron Jeremy , DeSario Paul A. , Brintlinger Todd , Baturina Olga A , Stroud Rhonda , Rolison Debra R. 
Published: February 2020

We demonstrate that composite catalytic aerogels represent a superior materials design motif for the creation of solar fuels photocatalysts. We couple surface plasmon resonant (SPR) guests to the inherent compositional and interfacial design flexibility of catalytic aerogels to photogenerate molecular hydrogen (H2). We investigate the effects of synthetically modifying the TiO2 aerogel network and the nanoparticulate Au||TiO2 interfaces in plasmonic Au–TiO2 aerogels on H2 evolution under both broadband (i.e., UV + visible light) and visible excitation. We also introduce non-plasmonic Pt co-catalyst nanoparticles into our composite aerogels, creating Au–TiO2/Pt aerogels that perform visible light SPR-driven photocatalytic reduction of water to generate H2.
The fuels production achieved with this multicomponent photocatalytic nanoreactor demonstrates that the nanostructured high-surface-area network in the aerogel can spatially and effectively separate charge while electrochemically connecting plasmonic nanoparticle sensitizers and metal nanoparticle. In doing so, we prove several crucial concepts: (1) integration of a plasmonic sensitizer with a separate water reduction co-catalyst within the ultraporous aerogel nanoarchitecture; (2) wiring the electron–hole pairs generated under visible light at the plasmonic Au||TiO2 interface to the co-catalyst via the nanoscale TiO2 network; and (3) combining both the photocatalytic oxidation and reduction reactions critical to solar fuels photocatalysis into one composite material at length scales compatible with the reaction kinetics.
This work is supported by the Office of Naval Research.
(Invited) Photoelectrochemical Hydrogen Evolution Based on Plasmon-Induced Charge Separation
Authors: Tatsuma Tetsu , Kao Kun-Che , Wu Ling , Kuroiwa Yoshinori , Nishi Hiroyasu 
Published: February 2020

Plasmon-induced charge separation (PICS) occurs at the interface between plasmonic nanostructures of gold, silver, or copper and a semiconductor such as titanium oxide.1-3 PICS involves energetically uphill transfer of electrons (or holes) from the plasmonic nanostructure to the semiconductor, so that the active carriers are retained in the semiconductor for a certain period of time and used for electrochemical reduction (or oxidation). We reported PICS for the first time more than 10 years ago1-3 and studied its mechanisms1-6 and applications2,3 including photocatalysis. We have reported oxidation of alcohols and aldehydes by PICS,1 and recently worked on photocatalytic reduction of water to hydrogen based on PICS at gold nanoparticle/titanium oxide systems.
We coated an indium-tin oxide transparent electrode with a titanium oxide thin film. We deposited a hexagonal array of small plasmonic gold nanoparticles on the titanium oxide film, followed by deposition of cocatalysts such as platinum nanoparticles. This working electrode was connected with a counter electrode such as a platinum wire and those electrodes were immersed in an electrolyte solution containing an electron donor such as methanol. The working electrode was irradiated with visible light, and hydrogen was evolved at the counter electrode even without bias voltage application, although the hydrogen evolution rate was enhanced when a bias voltage was applied. We will report optimization of the cocatalyst systems.
1. Y. Tian and T. Tatsuma, J. Am. Chem. Soc., 127, 7632 (2005).
2 . T. Tatsuma, Bull. Chem. Soc. Jpn., 86, 1 (2013) [account].
3. T. Tatsuma, H. Nishi, and T. Ishida, Chem. Sci., in press (doi: 10.1039/C7SC00031F) [review].
4. E. Kazuma and T. Tatsuma, Adv. Mater. Interfaces, 1, 1400066 (2014).
5. H. Nishi and T. Tatsuma, Angew. Chem. Int. Ed., 55, 10771 (2016).
6. K. Saito, I. Tanabe, and T. Tatsuma, J. Phys. Chem. Lett., 7, 4363 (2016).
(Invited) Plasmonic Driving of Chemical Reactions
Authors: Wang Jianfang 
Published: February 2020

Noble metal nanocrystals, possessing localized surface plasmon resonance, can interact strongly with light, efficiently converting light into heat and generating hot electrons and hot holes. Both plasmonic photothermal conversion and generation of hot charge carriers can accelerate chemical reactions. While the acceleration of chemical reactions by photothermal conversion is straightforward, the driving and acceleration of chemical reactions by plasmonic hot charge carriers represents a new research field. Plasmonic hot charge carriers can not only enhance the reaction yield and selectivity, but also introduce new reaction pathways. A full understanding of the latter process requires the knowledge of localized plasmon, electron/hole dynamics, charge transfer, and electron/hole-induced reactions. The study of plasmonic driving of chemical reactions will be rewarding in both fundamental and technological aspects.
The lifetime of plasmonic hot charge carriers is on the femtosecond scale. Without utilization, they will rapidly relax, converting their energy into heat. Two approaches have mainly been developed to facilitate the utilization of plasmonic hot charge carriers. The first is the integration of Au or Ag nanocrystals with Pd or Pt nanoparticles. Au and Ag nanocrystals possess strong localized plasmon resonance, while Pd and Pt nanoparticles are excellent catalysts for a variety of chemical reactions. A combination of the two types of metal nanocrystals can lead to efficient light absorption and generation of plasmonic hot charge carriers, which can subsequently inject into molecules that are adsorbed on the Pd or Pt component. The second is the integration of plasmonic metals with semiconductors. A barrier is formed at the interface. The generated hot electrons and holes can quickly inject into the conduction or valence band and therefore get separated. The injected charge carriers can then drive chemical reactions. We have synthesized bimetallic nanocrystals as well as metal/semiconductor hybrid nanostructures to demonstrate plasmonic driving of chemical reactions by both approaches.
Demonstrating the Activity and Stability of Conformal RuO2 "Nanoskins" on Technologically-Relevant, 3D Electrode Suports for Water Oxidation in Acid Electrolyte
Authors: DeSario Paul A. , Chervin Christopher N. , Nelson Eric S. , Sassin Megan B. , Rolison Debra R. 
Published: February 2020

The commercial viability of many energy-storage and energy conversion devices is compromised by limited efficiency in oxidizing water to generate molecular oxygen (OER). Current state-of-the-art OER anodes fail to meet device-relevant rates of water oxidation at reasonable potentials and suffer from poor stability at the high oxidizing potentials they must adopt to sustain device-relevant O2 generation. Additionally, the high cost and scarcity of the most promising OER catalysts―RuO2 and IrO2―have motivated the search for electrode designs that deploy a nanoscopic amount of the active material while maintaining activity and stability. Most thin film preparations of IrO2 and RuO2 are not amenable with insulating supports and/or non–line of sight geometries. We leverage our solution-based electroless synthetic protocol to deposit conformal, ultrathin films of RuO2 (“nanoskins”) on three-dimensional supports and benchmark their activity under device-relevant conditions. When a self-wired RuO2 thin film is expressed as a nanoshell around the fibers in commercially available SiO2 paper, RuO2@SiO2 electrodes exhibit current densities (10 mA cm–2 @ η=280) 25-times higher than when expressed on planar, conductive supports. By wrapping the fibers with conductive graphitic carbon before nanoskin deposition, we retain the high specific activity of RuO2 nanoskins (40–60 mA mg–1 @ η=330 mV) and preserve the desirable macroscale properties of SiO2 fiber paper: porous, lightweight, flexible, and inexpensive. By efficiently expressing the electrocatalyst, we innately restrict the oxidizing potentials needed to meet a given rate of water oxidation, which diminishes dissolution of the catalyst and corrosion of its underlying current collector, thereby extending anode lifetime.
On the Evaluation of Charge Transport and Reaction Kinetics in Z-Scheme Semiconductor Particles for Solar Water Splitting
Authors: Bala Chandran Rohini , Ardo Shane , Weber Adam Z. 
Published: February 2020

Solar water splitting is a promising approach to convert and store solar energy in the form of stable chemical bonds. A tandem particle-suspension reactor design1 (shown in Figure 1), comprising semiconductor particles (photocatalysts) suspended in an aqueous solution to effect Z-scheme water splitting in the presence of soluble redox shuttles, is considered here. Using a device-scale numerical model1, we identified reactor designs and concentration of photocatalysts and redox shuttles to yield up to 3.8% solar-to-hydrogen conversion efficiency with diffusion-driven species transport. Higher energy conversion efficiencies are predicted with natural convection facilitated species mixing. In this design, each semiconductor particle is wetted by electrolyte that contains at least four chemical species that can be involved in redox reactions on the particle surface. Therefore, selective surface catalysis becomes crucial to achieve high solar-to-hydrogen conversion efficiencies. In the present study, we develop a numerical model to evaluate the transport and kinetics of photogenerated charge-carriers inside a spherical semiconductor particle and across the semiconductor–electrolyte interface. The potential distribution within the particle is obtained by solving the Poisson-Boltzmann equation self consistently with the charge-carrier transport equations. The fluxes of the majority and minority charge-carriers across the semiconductor–electrolyte interface take into account all plausible redox reactions at the interface. Modeling results elucidate the dependence of the reaction selectivity on not only the kinetic parameters, but also on variables such as irradiance, operating temperature, particle size, recombination pathways and the electrolyte electrochemical potential. Results are further interpreted to identify strategies to boost the energy conversion efficiency for Z-scheme water splitting systems.
References
(1) Chandran, R. B.; Breen, S.; Shao, Y.; Ardo, S.; Weber, A. Z. Meet. Abstr.
2016, MA2016-01 (38), 1919–1919.

Figure 1
Multiphysics Modeling of Gas Diffusion Electrodes for CO2 Reduction
Authors: Weng Lien-Chun , Bell Alexis T. , Weber Adam Z. 
Published: February 2020

One of the main challenges towards achieving high efficiency solar fuel generators performing carbon dioxide reduction is the mass transport limitations in traditional aqueous systems. Typically, the current density for liquid phase carbon dioxide reduction is limited to approximately 10 mA/cm2 due to concentration polarization near the cathode surface.1This can be overcome by introducing a gas diffusion electrode, which allows vapor phase carbon dioxide to be fed directly to the catalyst, significantly decreasing the diffusion length.
Experiments have shown almost two orders of magnitude improvement in efficiency for vapor-fed devices compared to traditional aqueous systems.2,3 This improvement is most likely due to a higher surface area in the porous electrode and an increased diffusivity of gas phase CO2. For this work, we have developed a multiphysics model for gas diffusion electrodes that simulates species transport in gas phase, liquid phase and solid phase, charge transport, and (electro)chemical reaction kinetics. The model will focus on understanding transport of species in and out of the catalyst layer, and investigate the effects of gas diffusion electrode properties such as thickness, porosity and hydrophobicity on cell performance.

Acknowledgements

This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993.

References

Singh, M. R.; Clark, E. L.; Bell, A. T., Physical Chemistry Chemical Physics, 2015, 17(29), 18924-36.

Verma, S.; Lu, X.; Ma, S.; Masel, R. I.; Kenis, P. J. A., Physical Chemistry Chemical Physics, 2015, 18, 7075-7084.

Kim, B.; Hillman, F.; Ariyoshi, M.; Fujikawa, S.; Kenis, P. J. A., Journal of Power Sources, 2016, 312, 192-198.