bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Europe Section Heinz Gerischer Award) A Perspective of Photoelectrochemistry: Past Expectations and Present Realities
Authors: Heller Adam 
Published: February 2020

It was Heinz Gerischer who got me interested in and taught me semiconductor electrochemistry when he visited me just after the Oil Crisis of 1973. He, I and later many others dreamed of a world powered by semiconductor-liquid junction solar cells, hoping that that these would be simpler and cheaper than the silicon p-n junction solar cells that powered at the time communication satellites, remote terrestrial communication relays, wristwatches, calculators and other portable electronic devices. By 1981 research on the semiconductor -liquid junctions led to the uncovering of truths of nature and to 12 % solar conversion efficiencies, both to electrical power and in the generation of hydrogen. However, I did not see how efficient photo-electrochemical conversion could provide a technological edge over all-solid silicon and thin-film solar converters, because their packaging cost were lower and their stability was superior. After 34 years of fine research leading to solar conversion efficiency now at 20 %, packaging cost and stability still prevent photo-electrochemical solar converters from being preferred over all solid solar cells.
In the absence of technologically relevant semiconductor-liquid junction based solar converters we joined Akira Fujishima and Kazuhito Hashimoto in their quest for technologically relevant photo-catalytic surfaces that clean themselves of accumulating organic grime by catalyzing its air oxidation. On the fundamental side, the truth that Heinz Gerischer and I uncovered during his repeated stays at the University of Texas in Austin has been that the rate of the n-TiO2 –photo-catalyzed O2 oxidation of organic matter was not controlled by the rate of photo-generation of holes, but by the rate of reduction of adsorbed O2 by trapped electrons. On the practical side, we developed photo-stable binders that allowed the incorporation of photo-catalytic n-TiO2 in coatings; and a method of producing self-cleaning window glass.
Surface Chemistry of Electrocatalysts for CO2 Reduction to Fuels
Authors: Kronawitter Coleman X. , Chen Zhu , Zhao Peng , Koel Bruce E. 
Published: February 2020

The surface chemistry of electrocatalysts for the production of fuels by CO2 reduction was explored by surface science model studies using high-resolution spectroscopy and atomic scale imaging, as well as by electrochemical analysis of active electrodes. Using an experimental surface science approach, ultrahigh vacuum conditions were used to facilitate the fabrication of highly characterizable electrode-adsorbate systems. We have utilized a range of techniques for surface analysis to determine the structure and properties of single-crystal surfaces and unique alloys formed by vapor deposition under controlled conditions. Specifically, XPS, LEIS, LEED and STM were used to characterize the composition and structure of III-V semiconductors and bimetallic model catalysts. TPD, UPS, and vibrational spectrocopy using HREELS and IRAS were used to study the binding and electronic structure of adsorbates.
Many of our experiments are designed to explain the role of the electrode surface in the high selectivity observed in pyridine and other N-heterocycle-catalyzed CO2 reduction systems. We examined the preferential adsorption sites, bonding interactions, and reactivities of these molecular catalysts and other relevant adsorbates on the surfaces of photoactive electrode materials. Ambient pressure photoemission spectroscopy (APPES), STM, and vibrational spectroscopies were used to study the interaction of water and CO2 reduction catalysts with the surfaces of III-V semiconductors.
We have applied these techniques to also study bimetallic alloy electrocatalysts. Bimetallic alloys have been shown to exhibit lower overpotentials for CO2 reduction to fuels when compared to their metal constituents. By tuning the composition of the alloys, one can influence the binding of adsorbates and therefore reaction selectivity. We synthesized bimetallic surface alloys in controlled UHV environments to investigate the relationship between surface composition and electronic structure. We studied the interaction of relevant adsorbed species with the bimetallic alloy surfaces using TPD, IRAS, HREELS, and UPS to begin to understand the surface chemistry of these electrodes.
In parallel to these surface science investigations, we studied the electrochemical behavior of single crystals and bimetallic alloys. The purpose of these studies is to correlate CO2 reduction product selectivity to the quantitative measurements of surface chemistry made in UHV discussed above. Specifically we examined the relationship between electrochemical activity, surface composition, and the binding strengths of intermediates along CO2 reduction pathways. This work aids development of a molecular-level understanding of the heterogeneous processes involved the reaction mechanisms of efficient electrocatalytic fuel generation.
This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0012455.
Photocatalytic Coversion of CO2 By H2o As an Electron Donor Using Various Solid-State Photocatalysts
Authors: Teramura Kentaro 
Published: February 2020

The use of heterogeneous photocatalysts to reduce CO2 into storable feedstock is of particular interest because of its simplicity and low cost of operation. We have reported that CO as a main product is obtained for the photocatalytic conversion of CO2 in the presence of H2 over ZrO2, MgO, ATaO3 (A = Li, Na, and K), and Ga2O3, of which Ga2O3 exhibited the highest conversion of CO2: 7.8% over 48 h of photoirradiation. Unfortunately, these bare metal oxides function as photocatalysts in the presence of H2O not for reduction of CO2 but for overall water splitting. As of late, we found that Zn-doped, Ag-modified Ga2O3 exhibits higher formation rate of CO and selectivity toward CO evolution than bare, Ag-modified Ga2O3 for the photocatalytic conversion of CO2 by H2O as an electron donor. An isotope experiment using 13CO2 and mass spectrometry clarified that the carbon source of the evolved CO is not the residual carbon species on the photocatalyst surface, but the CO2 introduced in the gas phase. In addition, stoichiometric amounts of evolved O2 were generated together with CO. Only in recent years, XAFS measurement identified that ZnGa2O4 is generated on the surface of Ga2O3; therefore, it suppresses the evolution of H2, which results in the higher selectivity toward CO evolution.
Mathematical Modeling of Solar-Fuel Generators
Authors: Stevens John , Xiang Chengxiang , Singh Meenesh , Chen Yikai , Weber Adam Z 
Published: February 2020

A solar-fuel generator is a multicomponent device composed of light absorbers, electrocatalysts, membranes, and electrolytes in a specific system geometry. The overall solar-to-fuel conversion efficiency of such a system depends on the performance and materials properties of the individual components as well as the design of the system. In this talk, efforts in the Joint Center for Artificial Photosynthesis (JCAP) aimed at the continuum-scale modeling of these various components will be presented. In particular, the tradeoffs between the transport phenomena, kinetics, and photon capture will be detailed for different geometries and conditions. For example, the use of optically concentrating lenses can result in efficiency gains and lower cost systems, although the increased temperatures have both beneficial (e.g., transport properties and kinetics) and detrimental (light absorber efficiency and solvent stability) impacts that are ideally optimized through modeling. In addition, applications of the modeling framework to both hydrogen generation via water splitting and fuel formation via carbon reduction will be discussed, where the product distribution of the latter is heavily influenced by the local electrode overpotential.
SnO2 and F:SnO2 Inverse Opal Based Photoelectrochemcial Water Splitting
Authors: Kang Soon Hyung 
Published: February 2020

Nowadays, the exploration of new photoelectrode architectures to improve the light-harvesting and charge-collection properties of photoelectrochemical cells and related devices have been regarded as a challenging work. Here, we synthesized the inverse opal SnO2 for photoelectrochemical water splitting by the spin-coating method exploring the polystyrene beads with a size of approximately 350 nm. The SnO2 inverse opal structure shows the photonic crystal effect with a well-ordered hexagonal structure packing. Upon this film, the photoactive TiO2 layer with various thicknesses from 10 nm to 40 nm was deposited by atomic layer deposition. Herein, it is expected that an optimal TiO2 layer takes part in a role as a photoactive material. Adding to these results, the F doping on the SnO2 inverse opal film was also examined with the TiO2layers. These results were confirmed using Field-emission scanning electron microscopy, X-ray diffraction and ultraviolet-visible spectrophotometer. Detail results and discussion would be presented.

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Guiding Practical Pathways for Photo-Electrochemical Solar-Hydrogen Generation
Authors: Haussener Sophia , Dumortier Mikael 
Published: February 2020

Photo-electrochemical electrolysis of water provides a direct pathway for the conversion of solar energy into an energy-dense, storable and transportable fuel. The practical implementation of photo-electrochemical approaches requires focusing simultaneously on four key developmental concerns: device and system i) efficiency, ii) durability and reliability, iii) environmental sustainability, and iv) scalability with economic viability.
We developed a techno-economic model and coupled it to a life cycle assessment (LCA) in order to jointly assess efficiency, hydrogen cost, energy input, and lifetime/degradation of photo-electrochemical devices. The model we used accounted for optical losses in the concentrator, recombination and resistive losses in the photoabsorbers, overpotentials in the electrocatalysts (including mass transport limitations, relevant at high irradiation concentrations), as well as photoabsorber and electrocatalytic degradation. The sustainability assessment accounted for the energy input required for material mining and manufacturing of the device components, as well as operation. The cost assessment accounted for material and component cost and manufacturing. The model was used to investigate and compare a class of 16 devices: combinations of devices using i) concentrated or non-concentrated irradiation (irradiation concentration, C), ii) low quality Si-based or high quality III-V-based photoabsorbers, iii) earth abundant or rare electrocatalysts, and iv) integrated photoabsorber and electrocatalyst with the same or different absorber and electrolysis area (current concentration, F).
The results predict that maximum efficiency does not guarantee minimum hydrogen price or minimum energy demand, as depicted in figure 1 for a selection of devices. Devices using large irradiation concentration and III-V-based photoabsorbers showed low hydrogen prices and best efficiencies while non-concentrating devices using Si-based photoabsorbers and rare electrocatalysts showed slightly higher energy demand and hydrogen price. An increase in the component’s lifetime was generally beneficial to efficiency, cost, and energy demand. Degradation significantly influenced all three characteristics, and the calculations provided guidance for the most suitable exchange time of individual components – keeping overall device efficiency high while reducing energy and cost resulting from component exchange – during the lifetime of the complete device.
The coupled techno-economic-ecologic approach provides quantitative design guidelines for photo-electrochemical devices and can support decision-making for the implementation of large-scale, sustainable and competitive solar hydrogen production.

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Benchmarking Nanoparticulate Metal Oxides for the Alkaline Water Oxidation
Authors: Jung Suho , McCrory Charles C L , Peters Jonas C , Jaramillo Thomas F 
Published: February 2020

Nanoparticulate metal-oxide catalysts are among the most prevalent systems for alkaline water oxidation. However, comparisons of the electrochemical performance of these materials has been challenging due to the numerous methods of attachment and catalyst loadings used in the literature. Herein, we have identified a conventional drop-casting method that ensures adhesion of the catalysts and consistently applied to a variety of metal oxides for water oxidation reactions in alkaline condition. The nanoparticulate materials were characterized using XRD, XPS, BET, and SEM. The activity and Tafel slopes of the nanoparticulate catalysts attached by this method have been compared directly to similar systems synthesized by different methods such as electrodeposition, sputtering, etc. A brief discussion of the differences and similarities in the surface area as measured by BET and determined from the double-layer capacitance of the system is also provided.
Sol Gel Dip Coated Yb and Tm Doped Indium Oxide Dye Sensitizrd Solar Cells
Authors: Murali Kollegal Ramakrishna 
Published: February 2020

In2O3 thin films were deposited by the sol gel dip coating method adopting the following procedure. Clean ITO substrates were used for the deposition of the films. 10 ml of 0.33 M solution of Indium (III) nitrate was taken in a clean glass beaker. The solution was heated to 70˚C and the pH was brought to 9 by the addition of ammonia, then 1 gm of Acrylamide was added followed by the addition of 0.25 gm of N,N,bis methylene acrylamide. After 20 min, 5 mg ammonium persulphate initiator was added to this mixture. The solution became viscous. Cleaned microglass slides (2.5 cm x 7.5 cm) were immersed into the viscous solution and withdrawn at the rate of 1cm min-1. The film formed on the surface was dried in an air oven for about 15 min followed by annealing in air at different temperatures in the range of 350 - 500˚C for different durations in the range of 15 min to 90 min. Doping with Tm and Yb was done by adding 0.1 g of Yb(NO3)3 and 0.1 g of Tm(NO3)3 to the Indium nitrate solution before gelling. The doped and undoped films were dipped in N719 dye for 24 hours. a sandwich structure was formed by bonding the FTO substrate with dye coated In2O3 and a Pt counter electrode together through a hot-melt spacer, and a drop of electrolyte (0.60 M 1-butyl-3-methylimidazolium iodide (BMII), 0.03 M I2 was injected into the device through predrilled holes on the Pt counter electrode. DSSCs based on In2O3:Yb and In2O3:Tm were also fabricated via the same process.
The XRD patterns of the In2O3, In2O3:Tm and In2O3:Yb. . All the patterns can be assigned to cubic phase standard card (JCPDS 06-0416) without any additional diffraction peaks. The UV–vis absorption spectra of the doped and undoped In2O3 exhibit the absorption peak of the pure In2O3 about 3.85 eV, which is consistent with the results published, and it icreases to 3.93 eV and 4.00 eV respectively as Tm and Yb are doped into In2O3.
The J-V characteristics of the doped and undoped Indium oxide films indiacted that the Voc increased from 410 mV for undoped films increased to 530 mV and 630 mV for Tm and Yb doped films respectively. The Jsc increased from 2.45 mA cm-2 for the undoped films increased to 3.50 mA cm-2 and 4.25 mA cm-2 for Tm and Yb doping respectively.IPCE measurements indicated that for doped films the PCE was higher than that of undoped films. The fill factor of the films increased by doping with Tm and Yb. The larger Voc obtained with Yb doping can be explained on theb basis that the conduction band edge of Yb doped films is higher than that of undoped and Tm doped Indium oxide.
Electroreduction of CO2 to Synthesis Gas and Hydrocarbons on Doped Carbons
Authors: Varela Ana Sofia , Strasser Peter 
Published: February 2020

Strategies to close the anthropogenic carbon cycle through a renewable energy-driven efficient chemical conversion of CO2 into usable chemical feeds have become a scientific priority. Conversion of CO2 rich streams from steel mills, concrete- or coal-fired power plants, into syn-gas alcohols or hydrocarbons is of tremendous interest for industry. Of all chemical ways to convert CO2 into hydrocarbons, the electrocatalytic coupling of water splitting and CO2 reduction appears attractive, as it is a one-step process step, occurs at ambient temperature and pressures, involves solely water and CO2 as reactants, and may involve renewable electricity from wind, solar or hydro power plants.
CO2 electroreduction is typically carried out on the surface of metal catalysts. Cu catalysts generate various gas products such as H2, CO, methane and ethylene, while Au and Ag are the catalysts of choice for the selective electroreduction of CO2 into CO/H2 synthesis gas mixtures. On all metal catalysts the CO2 electroreduction suffers from prohibitively high kinetic overpotentials and limited product selectivity. This is why the identification of new catalysts or new catalyst formats, such as nanoparticles or core shell architectures, with reduced overpotentials combined with the exploration of new strategies to control and improve product selectivities has become the two key goals for CO2 reduction.
In this contribution, we share recent work on the electroreduction of CO2. In particular, we discuss a family of heteroatom-doped carbon catalysts for the generation of synthesis gas. We show evidence that carbon catalysts meet and exceed the activity and selectivity of traditional Au catalysts providing an intriguing cost-effective alternative.
Fully Integrated Stand-Alone Device for Gas-Phase CO2 Reduction Using Sunlight: Proof of Concept
Authors: Arab Mobin , Church Tamara L. , Li Xiaobo , Maschmeyer Thomas , Minett Andrew I. 
Published: February 2020

The conversion of CO2 to fuels can be a promising pathway to reduce the carbon intensity of the economy, if the energy required for its conversion is supplied from renewable sources. We showcase a fully integrated, wireless, stand-alone unbiased photoelectrochemical cell (PEC) for the conversion of CO2 and H2O to chemicals and fuels in gas phase. Simulated sunlight at 1 Sun intensity is used to drive the conversion reaction. Proof-of-concept experiments show that the device is operational in dilute CO2 streams (10% CO2, 2% H2O, Ar balance) as well as in concentrated CO2 streams (98% CO2, 2% H2O). With a Cu sheet as the cathode catalyst, the device offers a CO2 reduction selectivity of ~50%; when Cu2O nanorods are employed, the selectivity toward CO2 reduction increases to ~90%. Experiments related to improving the performance of the device, testing other catalyst materials, and detecting the products is ongoing. The cell is lightweight, built of earth-abundant materials, and easy to assemble and scale. Further, it operates in dilute CO2 streams and the gas-phase operation facilitates the separation of liquid products. Thus the device represents a promising avenue toward the direct conversion of CO2 from flue gas or even air, without the need to first capture the CO2.
Figure 1- Chronoamperometry experiments when the device is under interval illumination with difference cathode materials; a) Cu2O Nanorods, b) Cu sheet.

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Magnetic Fields That Enhance the Rates of Multistep Reactions Important in Energy Storage and Conversion
Authors: Gellett Wayne L. , Lee Heung Chan , Reed Jessica Jewett , Leddy Johna 
Published: February 2020

Reactions at the electrode solution interface are ubiquitous and integral in electrochemical generation and storage systems. As the number of steps in the electron transfer process increases, the probability of reduce energy efficiency increases through undesirable side reactions and slow steps. When the electron transfer step slows the overall reaction rate, electrocatalysts can increase net efficiency.
Incorporation of magnetic microparticles to the electrode has been shown to increase the efficiency of various electrochemical energy systems that include fuel cells, batteries, photovoltaics, and supercapacitors. It is generally observed that energy and power are increased by 40 % on incorporation of magnetic microparticles.
Every interfacial electron transfer process is composed of multiple steps. The simplest model is mass transport of the reactant to the electrode surface, the electron transfer, and mass transport of the product into the solution. In multistep processes, additional steps may be important such as adsorption, multiple electron transfers, and chemical reaction on the surface or in the bulk. The electron transfer step is usually envisioned as a simple charge transfer. However, the electron transfer includes transfer of charge and spin. Magnetic properties of the electron and molecular entities arise through the spin. Addition of magnetic microparticles alters the rates of interfacial electron transfers.
Here, three examples of magnetoelectrocatalysis in reactions important to electrochemical generation and storage are presented. In each of these systems, chemically inert micromagnets are held to the electrode surface in a coating of Nafion (R). In these reactions, there are components of mass transport, adsorption, interfacial spin and charge transfer, and surface reactions.

The hydrogen evolution reaction (HER) is facilitated at magnetically modified, single crystal p-Si. Overpotential is reduced >500 mV on magnetic modification.

Hydride storage in palladium is improved as the interfacial rates of H∙ transfer are increased by several orders of magnitude and overpotentials reduced by several hundred millivolts.

CO oxidation on platinum occurs near the thermodynamic potential at room temperature in water. The overpotential is reduced 600 mV with micromagnets.

In each of these technologically important reactions, magnetic microparticles increase the rates of inherently slow, interfacial reactions. The effect is a physical interaction wherein magnetoelectrocatalysis effects substantially increased rates of electron transfer.