bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Keynote) Cathodic Electrocatalysis Mediated By Polyoxometalates: Reduction of Carbon Dioxide and Reductive Activation of Molecular Oxygen for Hydrocarbon Oxidation
Authors: Neumann Ronny 
Published: February 2020

The talk will report on recent developments in our laboratory in electrochemical reactions catalyzed by polyoxometalates. First, combining a specifically designed di-Re(I) catalyst with H3PW12O40 in a hybrid compound, we show that upon electrochemical reduction of the polyoxometalate at a relatively low negative potential of 1.3 V versus Ag/AgNO3, photoexcitation of the polyoxometalate with visible light is enabled through excitation of the intravalence charge transfer band. This leads to electron transfer to the Re(I) catalyst for the overall photoelectrochemical reduction of CO2 to CO. Conceptually this means that such a polyoxometalate can be an electron “shuttle” between a water oxidation reaction on the one hand that produces electrons/protons and O2 and a CO2 photoreduction catalyst. Second, tri-transition metal substituted polyoxometalates such as b-[SiW9O37(CuIIH2O)3]10– are shown to be outstanding electrocatalysts for the selective reduction of CO2 to CO with a turnover frequency by foot-of the wave analysis of nearly 3000 sec–1 without addition of an acid. Very high stability in electrolytic reactions was observed with stable currents for a period of 24h. at a potential of 2.5 V versus Fc/Fc+ and a Faradaic efficiency of >90%. Step-wise reduction of the catalyst followed by UV-vis and EPR spectroscopy indicates that the active species is a likely a four-electron reduced polyoxometalate. Additionally, similar compounds such as b-[SiW9O37(FeIII
2NiIIH2O)3]10– are shown to be functional models of CO hydrogenase/CO2 dehydrogenase enzymes that also have Fe-Ni active sites. As in the enzyme, the CO oxidation is one order of magnitude faster than the CO2 reduction.
An iron-tungsten oxide inorganic molecular catalyst, a Keplerate polyoxometalate with a capsular structure, with a short-hand notation, {Fe30W72}, was used for the cathodic oxidation of simple hydrocarbons such as ethane to acetic acid, ethylene to formaldehyde and benzene to phenol in water. The {Fe30W72} capsule is stabilized in the core by sulfate/bisulfate anions providing a protic environment where three iron atoms are located at each of the twenty pores of the capsule leading to a unique and potent active site for the aerobic hydrocarbon oxidation. This is the first example of the reductive electrochemical activation of O2 that functionally mimics the reactivity of iron-based monooxygenase enzymes. Turnover frequencies based of 300-600 min1– were obtained based on the surface area of the cathode. With a graphitic carbon fiber cathode and Pt anode Faradaic efficiencies of ~60% at a cell potential of 1.8 V were typically obtained where the uncoupled reduction of O2 to water was minimized. Extensive mechanistic research using EPR spectroscopy, kinetic isotope effect measurements as well as reactions of model compounds such a 1,4-difluorbenzene, indicate the intermediacy of a highly active high spin iron-oxo species as the oxygenating species.
(Keynote) Tuning the Activity and Selectivity of CO2 Electroreduction Catalysts through Nanostructuring and Controlled Oxidation
Authors: Roldan Cuenya Beatriz 
Published: February 2020

CO2 electroreduction (CO2RR) into useful chemicals and fuels is a promising technology that might be utilized to minimize the impact that the increasing industrial CO2 emissions are having on the environment. In this talk I will discuss the use of O2-plasma treatments and pulsed potential CO2 electrolysis for the activation of nanostructured metallic surfaces and the re-generation of surface oxides.
Although plasma-oxidized silver surfaces were found to display a considerably decreased overpotential for the production of CO, the hydrogen evolution reaction (HER), a competing reaction against CO2 reduction, was found to increase over time. More stable and C1-product selective SnOx/AgOx catalysts will be presented. Additionally, a direct correlation between the presence of Cu2O on well-defined single crystal and nanostructured Cu surfaces and the enhanced production of C2+ products will be illustrated.
Electrochemical tests combined with ex situ SEM/TEM-EDS, quasi
in situ XPS, operando EC-AFM and XAFS data will be used to extract correlations between the activity, selectivity and stability of CO2RR catalysts and their morphology, structure, composition, and chemical state.
(Keynote) Electroreduction of CO2 on Pb and Bi Nanoneedles
Authors: Guay Daniel , Fan Mengyang , Garbarino Sebastien , Tavares Ana C , Prabhudev Sagar , Botton Gianluigi A. 
Published: February 2020

The rise in atmospheric CO2 concentration since the beginning of the Industrial Age has raised concerns on its potential effect on global temperatures. While several factors such as natural climate changes, variations in solar activity, and volcanic eruptions may also contribute to observed variations in CO2 concentrations, it has been well established that anthropogenic emissions contribute to the annual emission of over 30 billion tonnes of CO2, only about half of which is recycled through natural pathways.
CO2 conversion into value-added products is an avenue explored to mitigate environmental issues. Conversion methods appear promising, as they offer the potential to produce liquid and gaseous fuels for use either in the aeronautics industry, or as a chemical storage method for the intermittent energy produced by windmills and photovoltaic panels. Fuel synthesis may be achieved via either the production of a syngas mixture (H2 and CO) through the water gas shift reaction and subsequent conversion into hydrocarbon fuel through processes such as Fisher-Tropsch, or by direct electrochemical reduction of CO2. While all methods may result in similar conversion yields, depending on the catalyst used, direct electrochemical conversion of CO2 into value-added products is a low-temperature process, with the further advantage of requiring relatively simple equipment.
Formic acid, or formate salts, are used in a variety of chemical processes such as electrowinning, leather tanning, and aircraft de-icing. Alternatively, formic acid and formate salts may be considered a hydrogen storage medium. Direct formic acid, and more recently, direct formate fuel cells, have been investigated in the literature as they demonstrate significant benefits over methanol fuel cells, including higher open circuit voltage and lower crossover.
Among earth-abundant CO2 electrocatalysts, Sn, Pb and Bi are known to be highly selective for formate production, with faradic efficiency (FE) > 90%. However, several challenges need to be addressed for these materials to become viable alternatives for industrial applications based on an ERC process to become economically viable. In particular, issues related with large overpotential and low current densities need to be addressed, along with the long term stability of electrodes.
In this study, we compared the activity and stability for CO2 electroreduction of high surface area metallic Bi and Pb nanoneedles (see Figure 1). In both cases, the materials films were prepared through a direct electrodeposition (potentiostatic method). Both types of films were extensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and x-ray diffraction (XRD), while electrochemical activities were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and potentiostatic measurements.

Figure 1
Chemically Regenerative Redox Fuel Cell As Alternative to Conventional Proton Exchange Membrane Fuel Cell
Authors: Blanchard Pierre-Yves , Donzel Nicolas , Dupont Marc , Rozière Jacques , Jones Deborah J. 
Published: February 2020

Here we present the development of a non-conventional fuel cell with a liquid redox cathode. The originality of the project comes from the regeneration of a redox mediator in an additional tank outside of the cell. Instead of oxygen classically used at the cathode, a liquid catalyst is reduced and a fuel (H2) is oxidized at the anode. This system is called a chemically regenerative redox flow cell (CRRFC). This technology allows to answer both issues i.e. price (Platinum free cathode) and chemical stability (absence of ROS at the interface electrode/membrane).
Few examples of chemically regenerative redox fuel cell have been described in the literature[1] with different redox couples (NO3-/NO2-,[2] polyoxometalate[3]). The best performances have been obtained with polyoxometalate derivatives developed and commercialized recently by the ACAL-energy company.[4] The Flowcath® technology is based on a polyoxometalate (POM) solution as catholyte. Their technology has been able to provide energy during more than 10,000 hours. The major issues arising from their technology are the crossover of the polyoxometalate and the efficiency during regeneration process.
In this study, we first synthesize and characterize molecules as redox mediator to carry electron between the regenerator and the electrode. The redox molecule belongs to the family of polyoxometalate containing vanadium moiety. These molecules are a key element of the device and needs to answer some criteria such as a fast electron transfer, a redox potential below 1.23 V vs. ESH and a fast chemical oxidation by dioxygen.
A specific cell stand has been developed with an additional tank to oxidize the redox mediator. All the challenge comes from the regenerator chamber in order to not be limited by mass transport of the oxidised species. Polarization curves have been recorded to give access to the cell performances.
[1] Tolmachev, Y. V.; Vorotyntsev, M. A. Russ. J. Electrochem.
2014, 50, 403–411, doi:10.1134/S1023193514020050.
[2] Han, S. B.; Kwak, D. H.; Park, H. S.; Choi, I. A.; Park, J. Y.; Kim, S. J.; Kim, M. C.; Hong, S.; Park, K. W. Angew. Chemie - Int. Ed.
2017, 56, 2893–2897, doi:10.1002/anie.201610738.
[3] (a) Ward, D. B.; Gunn, N. L. O.; Uwigena, N.; Davies, T. J. J. Power Sources
2018, 375, 68–76, doi:10.1016/j.jpowsour.2017.11.035. (b) Ward, D. B.; Davies, T. J. Johnson Matthey Technol. Rev.
2018, 62, 189–203, doi:10.1595/205651318X696800.
[4] Creeth, A. Pt-free PEM cathode technology with fundamental durability benefits: FlowCath®. Fuel Cells Bull.
2011, 2011, 12–15, doi:10.1016/S1464-2859(11)70126-2.
(Keynote) Promoting Electrochemical Oxygen Evolution in Acidic Media: Hydrophobic Stabilization of Earth Abundant Catalysts
Authors: Galan-Mascaros Jose Ramon , Garcés-Pinedaa Felipe , Yua Jiahao 
Published: February 2020

The oxygen evolution reaction (OER) is a key process in the general development of sustainable solar fuels, and essential in the progress/growth of an alternative hydrogen economy. This is a very demanding reaction, since a OER catalysts must be fast and efficient, but also stable and robust to high oxidation potentials, water, oxygen, acids or bases, etc. Several earth abundant metal oxides have appeared as excellent OER electrocatalysts in neutral and basic conditions, with multiple examples from different labs.1 However, the situation in acidic media is quite different. Only noble metal oxides are able to exhibit OER activity in acid, where the hydrogen evolution reaction (HER) is easier and faster, and proton exchange membrane can be used to separate the products, allowing to reach high currents. Transition metal oxides are unstable, whose structural integrity is pH dependent.
Recently, we have demonstrated how Co-containing polyoxometalates (POMs), molecular metal oxide fragments,2 are active OER catalysts in acidic conditions.3 Our strategy consists of incorporating water-insoluble salts of these POMs into a hydrophobic composite electrode, yielding very good stability and, remarkably, competitive electrocatalytic performance when compared with noble metals. We also disclosed that this strategy is also useful with bulk metal oxides of abundant transition metals, becoming a general approach for the development of cost-effective OER catalysts. In this communication we will present our latest results regarding acidic OER catalysis with POMs and bulk metal oxides, shedding some light into the origin of the hydrophobic-catalytic synergy for this electrochemical process.
[1] J. R: Galan-Mascaros, ChemElectroChem, 2015, 2, 37.
[2] H. Lv, Y. V. Geletii, C. Zhao, J. W. Vickers, G. Zhu, Z. Luo, J. Song, T. Lian, D. G. Musaev, C. L. Hill, Chem. Soc. Rev, 2012, 41, 7572.
[3] M. Blasco-Ahicart, J. Soriano-Lopez, J. J. Carbó, J. M. Poblet, J. R. Galan-Mascaros, Nat.
Chem.
2018, 10, 24.
Nanocrystalline Electro-Chemo-Mechanical Actuator Operating at Room Temperature
Authors: Makagon Evgeniy , Mishuk Eran , Cohen Sidney , Wachtel Ellen , Lubomirsky Igor 
Published: February 2020

Chemical expansion of a solid refers to dimensional change due to change in stoichiometry. Dimensional change due to charged defect redistribution in an electric field has been termed the electro-chemo-mechanical (ECM) effect. Such instability is clearly deleterious for batteries or fuel cells, but, as recently suggested, has potential for use in actuation[
1
]. A typical ECM actuator includes: electrode1\WB1\solid-electrolyte(SE)\WB2\electrode2, where WB denotes working-body solids with a large chemical expansion coefficient. The main advantage of ECM is that it can simultaneously deliver large strain and large stress, which is difficult to achieve with other actuation mechanisms. We have constructed a room temperature ECM nanocrystalline membrane actuator (2mm diameter and »2µm thick) with Gd-doped ceria as SE. We tested two alternatives for the WB’s: (1) metal/(metal oxide) or (2) ceria/metal nanocrystalline composite. Electrical and electromechanical measurements demonstrated that the actuator response with metal/metal oxide WB’s is limited by the rate of oxygen diffusion from the solid electrolyte to the metal surface. Actuators with ceria/metal composite WB’s provide shorter response time (»20sec) and larger vertical displacement (>3.5µm). Our findings suggest that ECM may become a viable actuation mechanism.
[1] J. G. Swallow, J. J. Kim, J. M. Maloney, D. Chen, J. F. Smith, S. R. Bishop, H. L. Tuller, K. J. Van Vliet, Nat. Mater. 2017, 16, 749.

Figure 1
Development of a Graphene-Nickel Composite Electrode for Hydroxyl Ion Sensing Applications
Authors: Jafari Behnaz , Botte Gerardine G. 
Published: February 2020

The control and measurement of hydroxyl ion (OH-) concentration in solution are crucial in numerous industrial applications, namely treatments of natural water and wastewater, and food industries [1]. However, no portable method has been reported to directly measure OH ion concentration[2].
This study aims to develop a portable nickel-based electrochemical sensor which directly detects OH ion. The sensor signal is based on the current produced by the following reaction that happens between the nickel electrode and the hydroxyl ions present in solution [3, 4];

Ni(OH)2(s)+OH−

⇄
NiOOH(s)+H2O(l)+e−

(1)

The analysis of the nickel reactions was evaluated by cyclic voltammetry. Furthermore, chronoamperometry measurements were performed for a nickel electrode in alkaline solutions and the results demonstrated mathematical correlation between the current and OH- concentration.
In order to maximize the sensitivity of the sensor, graphene-nickel composite electrodes were designed and used in the hydroxyl ion sensor. Graphene was synthesized by chemical vapor deposition (CVD) method and its characterization was carried out by Raman spectroscopy. Findings of this work will be presented.

References

Alam, P., et al., Highly Selective Detection of H+ and OHâ€“with a Single-Emissive Iridium (III) Complex: A Mild Approach to Conversion of Non-AIEE to AIEE Complex. Organometallics. 34(18): p. 4480-4490.

Sun, D., et al., A low-cost portable electrical sensor for hydroxyl ions based on amorphous InGaZnO4 thin film at room temperature. Sensors and Actuators B: Chemical. 239: p. 679-687.

Medway, S., et al., In situ studies of the oxidation of nickel electrodes in alkaline solution. Journal of Electroanalytical Chemistry, 2006. 587(1): p. 172-181.

Jafari, B., M. Muthuvel, and G.G. Botte. Development of a Portable Nickel-Based Sensor for Hydroxyl Ion. in Meeting Abstracts: The Electrochemical Society.
Electrochemical Determination of Copper(II) Ions in Soil of Cultivation of Vegetables with Use of Bordeaux Syrup
Authors: Sussuchi Eliana Midori , Silva Jonatas O. S. , Lima Jéssica B. S. , Carvalho Sanny W. M. M. , Farias Ravir R. , Victor Maurício M. 
Published: February 2020

Organic agriculture is growing and among the inputs produced are vegetables. Bordeaux syrup, prepared from lime and copper(II) sulphate, is able to protect them from the most common insects and diseases. Copper is responsible for important functions in the development of plants and is strongly related to the process of respiration and photosynthesis, for example. However, it can increase Cu2+ levels in vegetables and copper ions in high concentration in the soil can lead to problems for distribution of other ions important for the development of the plant and can cause diseases in the human body [1]. The development of modified carbon paste electrodes comes as a sensible, low-cost, and easy-to-move alternative for detection of this species [2-3]. In this study, a modified electrode with the organic ligand 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol, which was able to detect Cu2+ in soil samples of vegetables cultivation with use of bordeaux syrup through interactions involved in the formation of the metal-L complex.
The optimization of parameters resulted in better analytical signals in B-R buffer solution at pH 5.00 as the electrolyte, potential of - 0.4 V for 900 s for preconcentration, scan rate of 10 mV s-1 and amount of modifier of 5%. The electroanalytical method obtained linear behavior in the range of 1.00 10-8 to 1.30 10-7 mol L-1, linear coefficient equal to 0.994 for determination of copper with LQ = 5.05 10-9 mol L-1 and LD = 1.67 10-9 mol L-1 (Figure 1). The electrode is successfully applied for the determination of copper(II) in samples of soil.

Acknowledgements: FAPITEC, CNPq, CAPES, Corrosion and Nanotechnology Laboratory – NUPEG and CLQM (Center of Chemistry Laboratories Multi-users) from Federal University of Sergipe for the analysis support.
[1] J. Liu, J. Wang, S. Lee, R. Wen. Plos One. 13 (2018) 1-12.
[2] A. Nezhadali, S. Sadeghzadeh. Sens. Actuators, B. 224 (2016) 134-142.
[3] J. C. Santos, C.R.S. Matos, G.B.S. Pereira, T.B.S. Santana, H.O. Souza, L.P. Costa, E. M. Sussuchi, A.M.G.P. Souza, I.F. Gimenez. Microporous Mesoporous Mater. 221 (2016) 48-57.

Figure 1
(Invited) The Role of Electronic Bulk and Surface Structures for Efficient Photo-Electro-Synthesis
Authors: Jaegermann Wolfram 
Published: February 2020

For an effective conversion of solar energy to a chemical fuel a lot of different materials as well as device structures have been suggested but only very few provide technological competitive conversion efficiencies. Limitations and loss processes can be deduced from a detailed consideration of the involved photovoltaic and electrochemical elementary steps. Optimized performance can only be reached when the photovoltaic and electrolytic boundary conditions of integrated systems are comparable to those of separated devices with no extra loss due to the coupling process.
Feasible solutions seem to be possible for water splitting and H2-generation, as we will show with a number of investigations performed recently combining electrochemical investigations with surface science studies. Especially photoemission results on the demands on the bulk and surface electronic structure provide clear boundary conditions on the material’s and surface properties: i) the semiconductors must provide a wide splitting of quasi Fermi levels which will be provided by multli-junctions but hardly can be expected for low band gap oxides based on localized d electron states as e. g. hematite due to polaron formation. ii) the interaction of H2O and their intermediates directly onto the light energy converting junction must be avoided because of possibly formed surface states. As a consequence a buried junction is needed. iii) Photocatalytic converters must be prepared which uses different junction properties in opposing directions (Janus type surfaces) as proven for facet engineering or hetero structure formation.
In summary, we do believe that effective photoelectrochemical devices need the input of different disciplines and expertise ranging from solid state physics, surface science to electrochemistry. Based on an improved understanding of the correlation of material’s properties with the involved elementary steps promising advanced technological solutions seem possible.
(Invited) Electrochemistry for Sustainable Solar Photovoltaics
Authors: Tao Meng 
Published: February 2020

Commercial solar photovoltaic technologies such as Si and CdTe are traditionally considered to be in a separate domain from electrochemistry. Their device operation is governed by semiconductor physics and their production involves non-electrochemical processes such as diffusion, screen printing, fractional distillation, etc. However, electrochemistry will likely play an indispensable role in sustaining the commercial solar technologies. This talk will discuss three roadblocks to sustainable solar photovoltaics and how electrochemistry can remove these roadblocks: 1) storage of intermittent solar electricity, 2) scarce Ag used in today’s Si solar cells, and 3) high energy input in producing solar Si wafers. An off-grid route is proposed for solar electricity storage based on a closed loop of Zn↔ZnO [1], in which Zn rods are produced in a solar electrolyzer from ZnO. The Zn rods are shipped to homes, offices, factories, and electric vehicles to be inserted into mechanically-recharged Zn/air batteries, for electricity on demand. The spent Zn anodes are collected for regeneration of Zn in the solar electrolyzer. This Zn↔ZnO loop is advantageous over the H2↔H2O loop in terms of theoretical performance and technical readiness. Electroplated Al on Si is proposed to replace the screen-printed Ag electrode in Si solar cells [2]. 18% efficiency has been demonstrated in a Si solar cell with an electroplated Al front electrode and a screen-printed Al back electrode, i.e., an Ag-free all-Al Si solar cell. To overcome the high resistivity of the solar Si wafer, direct Al plating on Si without any seed layer is developed through light-induced Al plating. Direct Al plating on Si drastically simplifies the metallization process for Al, resulting in a significantly-lower cost than competing technologies. Finally, electrochemical refining of metallurgical-grade Si for solar-grade Si has been unsuccessful. While metals up to 99.99% purity are readily produced by electrolysis, solar-grade Si requires a purity of at least 99.99999%. This is coupled with non-electrochemical difficulties in Si purification such as oxidation of the Si anode and crystallinity of the Si cathode. An analysis will be presented on ultrapure materials by electrolysis [3]. The reason for unsuccessful Si electrochemical refining will be discussed through an analogy between electrochemical refining and fractional distillation. A revised method for electrochemical refining of Si is proposed.
[1] M. Tao, A Zn↔ZnO loop for terawatt-scale storage of solar electricity, 43rd IEEE Photovoltaic Specialist Conference (Portland, OR, 2016), p. 2011
[2] 1. L. Wang, W.-H. Huang, W. J. Shin, M. Tao, B. Deng, and D. Wang, Light-induced plating of aluminum on silicon in a Lewis acidic chronoaluminate ionic liquid, Journal of the Electrochemical Society, 165, D381 (2018)
[3] M. Tao, Impurity segregation in electrochemical processes and its application to electrorefining of ultrapure silicon, Electrochimica Acta, 89, 688 (2013)