bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enabling Solar Fuels Technology By High Throughput Discovery of Earth Abundant Oxygen Evolution Reaction Catalysts
Authors: Haber Joel A. , Gregoire John M. , Guevarra Dan , Jones Ryan , Shinde Aniketa , Becerra-Stasiewicz Natalie , Xiang Chengxiang , Slobodan Mitrovic , Jung Suho , Kisielowski Christian , Yano Junko , Jin Jian 
Published: February 2020

The High Throughput Experimentation (HTE) project of the Joint Center for Artificial Photosynthesis performs accelerated discovery of new earth-abundant photoabsorbers and electrocatalysts. We will describe several new screening instruments for high throughput (photo-)electrochemical measurements and summarize the discovery pipelines. This approach will be illustrated using the high throughput discovery, follow-on verification, and device implementation of a new quaternary metal oxide catalyst. Discovering improved electrocatalysts for the oxygen evolution reaction (OER) is of great importance for efficient solar fuels generation, regenerative fuel cells, and recharging metal air batteries. We report a new Ce-rich family of active catalysts composed of earth abundant elements, which was discovered using high-throughput methods to produce 5456 discrete compositions in the (Ni-Fe-Co-Ce)Ox composition space. The activity and stability of this new OER catalyst was verified by re-synthesis and extensive electrochemical testing of samples in a standard format in 1.0 M NaOH. Characterization of selected compositions by XRD, XPS, SEM, TEM, EDS, XRF mapping, and EXAFS both as-synthesized and after electrochemical testing, reveal the important of nanostructure to the observed electrochemical performance. The discovery of additional electrocatalysts by expansion of this composition space investigated and of new composition spaces tested for OER activity and stability under acidic conditions will be reported.
High-Efficiency Tandem Absorbers for Economical Solar Hydrogen Production
Authors: Deutsch Todd G , Young James L. , Döscher Henning , Wang Heli , Turner John A 
Published: February 2020

In this talk I will present an overview of our research strategy to develop a semiconductor-based device capable of over 20% solar-to-hydrogen efficiency with several thousand hours of stability under operating conditions. Our goal is to improve solar-to-hydrogen (STH) efficiency from 12.4% to over 20% by developing novel tandem semiconductor materials and configurations. Our approach focuses on classes of materials that have either demonstrated exceptionally high efficiency or theoretically can produce highly efficient materials. The four tandem material sets in our research portfolio are III-Vs on GaAs, InGaN on Si, III-V-N on Si, and dual photoelectrode pairings. We are evaluating catalytic nitride, oxide, and sulfide-based semiconductor surface modifications to extend durability from a few hundred hours to nearly 1000 hours, with a stretch target of 3500 hours. Cost reductions in the synthesis of high-efficiency III-V photoelectrochemical devices could be realized from emerging epitaxial synthesis technologies such as spalling, epitaxial lift-off, close-space vapor transport, or hydride vapor phase epitaxy to yield economical hydrogen production. Our group addresses synthesis cost, in a limited capacity, by investigating novel material configurations.
Within the next few years, we plan to demonstrate a prototype photoreactor that produces 3 L of standard hydrogen within an 8-hour period under moderate solar concentration (10x), which can be accomplished using only 6 cm2 of a 20% STH material.
Microfluidic Photocatalytic Device Utilizing Anodized Titania Nanotube Arrays: Application and Simulation Validation
Authors: Smith York R. , Jayamohan Harikrishnan , Hansen Lauryn , Mohanty Swomitra K. , Gale Bruce K. , Misra Mano 
Published: February 2020

Microfluidic photocatalytic reactors have advantages over conventional bulk reactors such as large surface-area-to-volume ratio and high control of fluid flow. Although titania nanotubular arrays (TNA) have shown enhanced photocatalytic degradation compared to nanoparticle films in a batch reactor configuration, their application in a microfluidic format has yet to be fully explored. The photocatalytic performance of a microfluidic reactor with TNA catalyst was compared with the performance of microfluidic format with TiO2 nanoparticulate (commercial P25) catalyst. The microfluidic device was fabricated using non-cleanroom based soft lithography, making it suitable for economical large-scale manufacturing. The photocatalytic performance was evaluated at different flow rates ranging from 25 to 200 μL/min. The TNA microfluidic system demonstrated enhanced photocatalytic performance over microfluidic TiO2 nanoparticulate layers, especially at higher flow rates (50-200 μL/min).
A computational model of the microfluidic format was developed to evaluate the effect of diffusion coefficient and rate constant on the photocatalytic performance. The improved performance of the TNA photocatalyst over the nanoparticle film can be attributed to higher generation of, and improved diffusion of oxidizing species. The model and microfluidic platform developed can easily be modified to suit other channel geometries and pollutants. A comparison of similar microfluidic photocatalytic platforms was made on the basis of dimensionless Peclet number. The system described in this study demonstrates high advective flow compared to otherwise similar microfluidic photocatalytic systems.
Enhanced Water Splitting at Thin Film WO3 Photoanodes Modified with the Electro-Catalysts
Authors: Solarska Renata , Bienkowski Krzysztof , Augustynski Jan , Kulesza Pawel J 
Published: February 2020

An effective solar light-driven water splitting in photo-electrochemical devices requires use of materials which combine high photo-conversion efficiency and long term stability. For the latter reason the choice of the suitable systems is restricted to the semiconducting oxides that, in most cases, do not undergo photo-corrosion in aqueous solutions and are able to absorb efficiently the visible light. However, although the nanostructured scaffold of the semiconducting photo-electrodes contributes generally to decrease the bulk charge recombination by reducing the minority charge carriers pathway to reach the solution species, at the same time, it tends to enhance the recombination of charges at the surface due to the increased contact area with the electrolyte. Common approach to reduce recombination losses, involves deposition at the photo-electrode surface of electrocatalysts allowing to overcome slow kinetics of oxygen evolution. There are only few, precious metal (Pt, IrO2), oxygen-evolution electrocatalysts that can be used in pH acidc in which WO3 operates effectively. In this regard, we will present an increase of water photo-oxidation currents at WO3 photo-anodes, caused by presence of polyoxometalates (POMs), such as phosphomolybdate (PMoO40
3-) Keggin type ions. This class of compounds is known to undergo reversible, stepwise multi-electron transfer reactions that are combined with their excellent proton conductivity. What is more, the POMs might act as a buffer layer when form a cover for a metallic nano - particles largely used as a regular catalysts. The POMs may act either as relays for photogenerated electrons or as catalysts directly involved in the hole transfer reactions. In particular, they may affect the pathway of water oxidation by modifying the stability of the intermediates (e.g., peroxides) involved in this processes. Ongoing efforts devoted to minimize the bias voltage required to perform visible light-driven photo-oxidation of water at NS WO3 photoanodes also include the use of dopants or incorporation of plasmonic metal nanostructures allowing to enhance the light capture by the WO3 films1.
1. R. Solarska, K. Bienkowski, S. Zoladek, A. Majcher, T. Stefaniuk, P. J. Kulesza and J. Augustynski, Angew. Chem. Int. Ed.
2014, 53: DOI: 10.1002/anie.201408374
Bismuth-Based Multimetal Oxides: Evaluation of Their Photoelectrochemical and Photocatalytic Properties
Authors: Subramanian Vaidyanathan 
Published: February 2020

One of the approaches used to improve the photocatalytic activity of single metal oxides is to use a foreign atom as a dopant to facilitate improved light absorbance/charge separation. Unlike, single metal oxides, using multimetal oxides offer the option to include an additional element as a defacto part of the structure to aid in tuning the band edge positions, improving light absorbance, and enhancing photocatalysis.
Of particular interest is the use of bismuth which allows the shifting of the valence band closer to the conduction band to reduce bandgap. In this presentation, bismuth titanates will be examined as a case study on multimetal oxides. BTO will be evaluated for its photocatalytic and photoelectrochemical properties. The role of 3d elements in altering the photocatalytic properties of the BTO is presented. Photoelectrochemical techniques can aid in the fundamental understanding of the charge generation, separation, and transport in such oxides. To this end, the electrochemical responses of the bismuth titanate films and the effects of a third element inclusion will be discussed.
The insights drawn from this work can aid in designing new formulations that represent other oxide family groups such as scheelites, delafossites, or perovskites.
Theoretical and Experimental Study of Cobalt Spinel Oxides for Solar Driven Hydrogen Production
Authors: Yan Yanfa 
Published: February 2020

Using sunlight and semiconductors to split water in a photoelectrochemical (PEC) process to generate hydrogen provides a viable way to produce renewable fuel. Metal oxide photoelectrodes are of particular interest due to their low cost and relatively high stability in aqueous media. Spinel Co-Fe-Al oxide system has shown the potential for PEC hydrogen production. The electronic and optical properties of Co based spinel oxides, CoX2O4 (X =Al, Ga, In) are calculated using first-principle density functional theory. We show that the desirable properties for solar photoconversion can be obtained by controlling the alloy compositions. The ability to manipulate the electronic and optical properties is attributed to the different s-orbital energies and sizes of the cations. Our calculated bandgaps as function of composition provide detailed practical guidance for synthesizing Co based spinel oxides with electronic and optical properties necessary to achieve high efficiency PEC decomposition of water for hydrogen production by sunlight. Our experimental work demonstrated the tunable band gaps and the PEC responses of the Co based spinel oxides.
Gold-Based Nanomaterials for Catalytic CO2 Conversion Applications
Authors: Matranga Christopher 
Published: February 2020

Managing carbon emissions is one of the most pressing issues currently faced by the energy sector. In addition to technical challenges associated with the capture and storage of CO2, are cost issues that make implementation of these technologies impractical. One interesting approach for dealing with these issues is to catalytically convert CO2 into liquid fuels, olefins, aromatics, and industrial chemicals that can be sold to offset carbon management costs. This approach requires the development of novel catalysts capable of utilizing carbon-friendly forms of energy to activate CO2 and drive a chemical reaction. My talk will focus on two Au-based catalyst currently being developed for CO2 applications. The first system is based on atomically precise Au25

q
clusters (q = -1, 0, +1) where we have manipulated the electronic structure and ground-state charge of the cluster to tailor its interaction with CO2, H+, OH-, O2 and other key species in order to improve electrocatalytic activity and direct chemical reaction pathways. The second system is based on Au-ZnO heterostructures where visible-light plasmonic excitations in Au nanoparticles are used to generate heat and drive chemical reactions on the ZnO substrate. These two systems demonstrate how the size of Au nanoparticles can be altered to create dramatically different electronic structures (bound vs. free electrons), modulate catalytic activity, and impact how we finally utilize these materials for different catalysis applications.Managing carbon emissions is one of the most pressing issues currently faced by the energy sector. In addition to technical challenges associated with the capture and storage of CO2, are cost issues that make implementation of these technologies impractical. One interesting approach for dealing with these issues is to catalytically convert CO2 into liquid fuels, olefins, aromatics, and industrial chemicals that can be sold to offset carbon management costs. This approach requires the development of novel catalysts capable of utilizing carbon-friendly forms of energy to activate CO2 and drive a chemical reaction. My talk will focus on two Au-based catalyst currently being developed for CO2 applications. The first system is based on atomically precise Au25

q
clusters (q = -1, 0, +1) where we have manipulated the electronic structure and ground-state charge of the cluster to tailor its interaction with CO2, H+, OH-, O2 and other key species in order to improve electrocatalytic activity and direct chemical reaction pathways. The second system is based on Au-ZnO heterostructures where visible-light plasmonic excitations in Au nanoparticles are used to generate heat and drive chemical reactions on the ZnO substrate. These two systems demonstrate how the size of Au nanoparticles can be altered to create dramatically different electronic structures (bound vs. free electrons), modulate catalytic activity, and impact how we finally utilize these materials for different catalysis applications.
Corrosion and Passivation of p-GaInP2 Photocathodes at Light-Dark Boundaries
Authors: Young James L , Döscher Henning , Deutsch Todd G , Turner John A 
Published: February 2020

The tandem GaAs:GaInP2 PV:PEC (photovoltaic:photoelectrochemical) cell has achieved a record 12.4% solar-to-hydrogen water splitting efficiency, but the instability of the p-GaInP2 PEC junction greatly limits device lifetime. We have developed surface modifications to stabilize p-GaInP2 for 300+ hours, but failure can often be associated with corrosion that initiates at photoelectrode edges, beneath stationary bubbles, and at defects. Common to these conditions that initiate corrosion, is the presence of sharp light-dark boundaries, which may accelerate corrosion. In this work, we investigate photo-corrosion behavior of p-GaInP2 at light-dark boundaries. A light-dark boundary was simulated by illuminating a ~2 mm diameter region at the center of a 6 mm diameter photoelectode and a set of durability tests were performed in 3M sulfuric acid at constant current. After each test, samples were analyzed with optical microscopy, profilometry, and SEM with EDS and the corrosion products in solution were quantified with ICP-MS. We observe a corrosion trench at the outer perimeter of the illuminated region and spatially-dependent corrosion features that correspond with the placement of the counter electrode as well as a region where corrosion is inhibited that corresponds with the direction of evolving H2 bubbles. To explain these observations, we will present a set of experiments and measurements to show how spatial variation in surface band bending and H2 saturation can explain corrosion characteristics at light-dark boundaries.
Efficient Photocatalytic Hydrogen Production By Ta2O5 Nanotube Powders Sputtered Decorated with Ni Nanoparticles
Authors: Gonçalves Rentao , Wender Heberton 
Published: February 2020

Modern life requires abundant and economical energy, and the sun is the best source of energy on earth. Research into materials and techniques which enable the transformation of energy from the sun has increased in recent decades due to the environmental problems associated with the use of fossil fuels. In this context, after the pioneering work of Honda and Fujishima using semiconductor photoanodes for water splitting,[1] photocatalytic hydrogen production has emerged as a low-cost alternative process for producing clean and renewable fuels. A number of oxide semiconductor photocatalysts, such as TiO2, NaTaO3 and Ta2O5, have been studied. They show reasonable photolysis efficiency, especially in Ta-based photocatalysts under UV light irradiation.[2-4] The photocatalytic activity can be drastically improved by loading NiO-Ni nanoparticle (NP) co-catalysts onto the surface of these Ta-based materials. In this respect, loading NiO-Ni NP co-catalysts onto Ta-based oxides has been reported as an important strategy for enhancing the overall activity of photocatalytic water splitting. Here we prepared very small Ni(0) nanoparticles (NPs) supported onto Ta2O5 nanotubes by magnetron sputtering deposition method. Ta2O5 nanotubes with 0.126 wt% of Ni showed superior photocatalytic activity for hydrogen production by water splitting when compared to pure Ta2O5 nanotubes, with a photonic efficiency estimated at 7.41%. In addition, insights into the role of Ni co-catalysts were obtained using in situ X-ray absorption spectroscopy (XAS) experiments performed at the Ta L3-edge and the Ni K-edge, both with and without simulated solar irradiation.
REFERENCES
1. A. Fujishima and K. Honda, Nature, 1972, 238, 37-38.
2. P. Zhang, J. Zhang and J. Gong, Chem. Soc. Rev., 2014.
3. Z. Zou, et al, Nature, 2001, 414, 625-627.
4. R. V. Gonçalves, et al, J. Phys. Chem. C., 2012, 116, 14022-14030.
Facile Synthesis of Ultrafine Nanoparticles of Iron Based Oxides and Their Application in Solar Cells
Authors: Ahmmad Bashir , Hayasaka Shogo , Kanomata Kensaku , Basith M. a. , Kubota Shigeru , Hirose Fumihiko 
Published: February 2020

Facile and eco-friendly methods have been developed for the fabrication of ultrafine nanoparticles of iron based oxides. Initially, mesoporous α-Fe2O3 nanoparticles were prepared by the green tea mediated hydrothermal method. The nanoparticles of α-Fe2O3 were highly pure and well crystallized with an average particle size of 60 nm. For the fabrication of ultrafine nanoparticles, the as-prepared α-Fe2O3 were dispersed in propanol and sonicated for 1.5 h. TEM analysis confirmed the formation of single-crystalline nanoparticles with a mean size of 15 nm. The ultrafine nanoparticles showed improved performance when applied in a solar cell. We also prepared Gd and Ti doped BiFeO3 microparticles by solid state reaction technique, which was then subjected to ultrasonication for the fabrication of ultrafine nanoparticles. The average particles size of the sample was found to be 12 nm. The ultrafine nanoparticles and their bulk counterparts were successfully applied to a solar cell.
Controlling Active Surface Area of TiO2 Nanotube Imprinted Ti Foils for Efficient Dye-Sensitized Solar Cells
Authors: Lin Lu-Yin , Yeh Min-Hsin , Chen WeiChieh , Ho KuoChuan , Ramamurthy Vittal 
Published: February 2020

The counter electrode (CE) of dye–sensitized solar cells (DSSCs) plays an important role for transferring electrons and catalyzing the I−/I3
− reduction. Active surface area of the substrate determines the reduction sites of the deposited catalyst as well as the catalytic ability of the CE. A simple and effective method for enhancing and controlling the active surface area of metal foils is provided in this study. The Ti foils are imprinted by TiO2 nanotubes (TNT) via anodization and ultrasonic vibration techniques. The active surface area of imprinted Ti foils is controlled by varying the anodization voltage to produce TNT imprints with different diameters and depths. A solar–to–electricity conversion efficiency (η) of 9.35% was obtained for the DSSC with a TNT–imprinted Ti foil as the CE substrate, while the cell with an imprints–free Ti foil shows an η of 7.81%. The enhanced η is due to the improved electrocatalytic ability of the CE by using the TNT–imprinted Ti foil as the substrate with higher active surface area.
The Structural Aspects of PFSA Ionomers As Determined By STEM and Simulations
Authors: Paddison Stephen J. 
Published: February 2020

The need for next generation polymer electrolyte membrane fuel cells (PEMFCs) has driven considerable research effort into the development of novel membrane materials that are highly proton conducting at low temperatures. At present, perfluorosulfonic acid (PFSA) ionomers are the electrolyte of choice in current PEMFCs. PFSA ionomers including the benchmark Nafion™, consist of a hydrophobic poly-tetrafluoroethylene (PTFE) backbone with pendant perfluorinated vinyl ether side chains each terminated with a sulfonic acid group (i.e., –SO3H). The chemistry and molecular structure of the side chains and backbone in PFSAs play a crucial role in determining the hydrated morphology and transport properties especially in the presence of water. Under hydrated conditions, the mesoscale phase separation occurs due to the hydrophobic and hydrophilic segments of the macromolecules. This is mainly due to the aggregation of ionic clusters and the reorganization of the PTFE backbones, which have been investigated by a variety of experimental and modeling approaches.
We have recently examined the morphology of dry and hydrated perfluorosulfonic acid (PFSA) ionomers at cryo and room temperature using TEM/STEM with EELS capability. Z-contrast imaging was utilized to identify the micro-phase separation of the hydrophilic side chains containing water and the hydrophobic polytetrafluoroethylene (PTFE) backbones. The results compare very favorably with hydrated morphologies obtained through mesoscale dissipative particle dynamics (DPD) simulations. The cryo-STEM images of plunge-frozen samples was also found to agree with morphologies based on SAXS experiments. Chain conformations of the perfluorosulfonic acid (PFSA) ionomers: Nafion™ and Aquivion® were investigated with electron energy-loss spectroscopy (EELS) on a 200 kV transmission electron microscope (TEM) equipped with a monochromator. The results were compared with polytetrafluoroethylene (PTFE) to evaluate the effect of the pendant perfluoroether side chains of the ionomers on the structure of the PTFE backbone. Several unique spectroscopic features corresponding to conformational changes were identified in the low-loss region and the fine structures of the carbon K-edge. Results obtained from high-level density function theory (DFT) based electronic structure calculations confirm the conformational dependence of the EEL spectra of the PFSA ionomers. Comparison with the spectra obtained from the experiments revealed the correlation between the specific side chain chemistry and backbone conformation. This spectroscopic information will allow us to further explore the morphological properties of these materials when combining with additional imaging techniques.