Evidence of Local pH Changes during Ethanol Oxidation at Pt Electrodes in Alkaline Media

Local changes of the interfacial pH can significantly affect the rate and mechanism during the course of an electrodic reaction. For instance, different pH values will have a significant effect on the equilibrium properties of both solution and surface species, altering the reactions kinetics. Ethanol oxidation at platinum electrodes in alkaline media involves the fast consumption of OH− species that will change the local pH at the electrode surface, decreasing the reaction rate. In this study, the local pH change during ethanol oxidation in alkaline media is accomplished by using rotating ring-disc electrode (RRDE) experiments. The current at the ring when polarized at the onset of hydrogen evolution serves as a measure of the local pH in the vicinity of the electrode. The results show that the current at the ring at 0.1 V (vs. RHE) becomes more negative during ethanol oxidation, owing to a change in the equilibrium potential of the hydrogen evolution reaction caused by a change in the local pH.

Silica Microparticles Supported Gold and Copper Ferrite Nanoparticles: A Magnetically Recyclable Bimetallic Catalyst for Sonogashira Reaction

Novel silica supported gold and copper ferrite nanoparticles (NPs) have been synthesized, characterized and used as a separable dual catalyst in Sonogashira type reaction. These Au.CuFe2O4@Silica NPs show a high efficiency as catalyst in the alkynylation not only of aryl iodides but also aryl bromides. By using only 0.5 mol% loading and t-BuOK as base in N,N-dimethylacetamide as solvent, aryl iodides react at 115 ºC in 1 d, whereas for aryl bromides the cross-coupling takes place at 130 ºC in 2 d. The catalyst can be successfully recycled using an external magnet for four consecutive runs.

Gold Nanoparticles Supported on Polyacrylamide Containing a Phosphorus Ligand as an Efficient Heterogeneous Catalyst for Three-Component Synthesis of Propargylamines in Water

Gold nanoparticles supported on a polyacrylamide containing a phosphinite ligand have been synthesized and characterized using different techniques such as TEM, SEM, EDX, XPS, and solid UV analyses. The new material was successfully applied as a heterogeneous catalyst for the three-component A3 coupling of amines, aldehydes, and alkynes to give propargylamines. Reactions are performed in neat water at 80 °C with only 0.05 mol% catalyst loading. The heterogeneous catalyst is recyclable during seven consecutive runs with small decrease in activity.

Oxidation of Ethanol and Its Derivatives on Well Defined Pt Single Crystal Electrodes Vicinal to Pt(111): A Comparative Study

The oxidation of ethanol (EtOH) at Pt(111) electrodes is dominated by the 4e path leading to acetic acid. The inclusion of surface defects such as those present on stepped surfaces leads to an increase of the reactivity towards the most desirable 12e path leading to CO2 as final product. This path is also favored when the methyl group is more oxidized, as in the case of ethylene glycol (EG) that spontaneously decomposes to CO on Pt(111) electrodes, thus showing a more effective breaking of the C-C bond. Some trends in reactivity can be envisaged when other derivative molecules are compared at well-ordered electrodes. This strategy was used in the past, but the improvement in the electrode pretreatment and the overall information available on the subject suggest that relevant information is still missing.

Improving the photoactivity of bismuth vanadate thin film photoanodes through doping and surface modification strategies

Currently, one of the most attractive and desirable ways to solve the energy challenge is harvesting energy directly from the sunlight through the so-called artificial photosynthesis. Among the ternary oxides based on earth–abundant metals, bismuth vanadate has recently emerged as a promising photoanode. Herein, BiVO4 thin film photoanodes have been successfully synthesized by a modified metal-organic precursor decomposition method, followed by an annealing treatment. In an attempt to improve the photocatalytic properties of this semiconductor material for photoelectrochemical water oxidation, the electrodes have been modified (i) by doping with La and Ce (by modifying the composition of the BiVO4 precursor solution with the desired concentration of the doping element), and (ii) by surface modification with Au nanoparticles potentiostatically electrodeposited. La and Ce doping at concentrations of 1 and 2 at% in the BiVO4 precursor solution, respectively, enhances significantly the photoelectrocatalytic performance of BiVO4 without introducing important changes in either the material structure or the electrode morphology, according to XRD and SEM characterization. In addition, surface modification of the electrodes with Au nanoparticles further enhances the photocurrent as such metallic nanoparticles act as co-catalysts, promoting charge transfer at the semiconductor/solution interface. The combination of these two complementary ways of modifying the electrodes has resulted in a significant increase in the photoresponse, facilitating their potential application in artificial photosynthesis devices.

Model of an Arizona gold mine.

no.1(1922)

Gold Company Claims, Witwatersrand, South Africa, 1895 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Bacon's new map of the Witwatersrand goldfields in the districts of Pretoria and Heidelberg, Transvaal, S. A. R. : shewing the main and other reefs, with the farms, gold mining company's claims and concessions : from information in the Surveyor-General's Department. It was published by G. W. Bacon & Co. in 1895. Scale [ca. 1:88,992].The image inside the map neatline is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator (UTM Zone 35S, meters, WGS 1984) projected coordinate system. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, roads, railroads, cities and other human settlements, administrative boundaries, farms, homesteads, main reefs, other reefs, probable connections, and mills. Includes also notes and inset: "Enlarged map of the farms Lanlaagte, Turffontein, Dornfontein & Elandsfontein, shewing the boundaries of the principal deep level gold mining coys. on the Witwatersrand goldfields" and a geological profile of the area north of Magaliesberg to the south of Witwatersrange.This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection. These maps typically portray both natural and manmade features. The selection represents a range of originators, ground condition dates, scales, and map purposes.

The Eurozone crisis and the erosion of democratic legitimacy: Lessons from the gold standard. ACES Cases No. 2013.3

This paper makes four propositions. First, it argues that the euro’s institutional design makes it function like the interwar gold exchange standard during periods of stress. Just like the gold exchange standard during the 1930s, the euro created a ‘core’ of surplus countries and a ‘periphery’ of deficit countries. The latter have to sacrifice their internal domestic economic equilibrium in order to restore their external equilibrium, and therefore have no choice but to respond to balance of payments crises by a series of deflationary spending, price and wage cuts. The paper’s second claim is that the euro’s institutional design and the EU’s response to its ‘sovereign debt crisis’ during 2010-13 deepened the recession in the Eurozone periphery, as EMU leaders focused almost exclusively on austerity measures and structural reforms and paid only lip service to the need to rebalance growth between North and South. As Barry Eichengreen argued in Golden Fetters, the rigidity of the gold standard contributed to the length and depth of the Great Depression during the 1930s, but also underscored the incompatibility of the system with legitimate national democratic government in places like Italy, Germany, and Spain, which is the basis for the paper’s third proposition: the euro crisis instigated a crisis of democratic government in Southern Europe underlining that democratic legitimacy still mainly resides within the borders of nation states. By adopting the euro, EMU member states gave up their ability to control major economic policy decisions, thereby damaging their domestic political legitimacy, which in turn dogged attempts to enact structural reforms. Evidence of the erosion of national democracy in the Eurozone periphery can be seen in the rise of anti-establishment parties, and the inability of traditional center-left and center-right parties to form stable governments and implement reforms. The paper’s fourth proposition is that the euro’s original design and the Eurozone sovereign debt crisis further widened the existing democratic deficit in the European Union, as manifested in rising anti-EU and anti-euro sentiment, as well as openly Eurosceptic political movements, not just in the euro periphery, but also increasingly in the euro core.

REACHING FOR BLUE GOLD - How the EU can rise to the water challenge while reaping the rewards. EPC Issue Paper No. 80, November 2015

Foreword. Climate change is bad news for water resources – and thus for human development, societies, economies, the environment, and local and global security. The increasing frequency and severity of extreme weather events such as droughts and floods serves as a reminder of the effects climate change can have on the quantity and quality of global water reserves, and thus on various other aspects of life. Even though the effects differ from region to region, this is a global challenge with far-reaching consequences to which Europe is not immune. As the world leaders gather in Paris in December 2015 to discuss a new international climate deal, it is worth to remind politicians, businesses and citizens of the water challenge and its wider implications, which already affect us today – and which will only get worse with climate change. However, water-related risks resulting from climate change are not a fatality and damage control doesn’t have to be the only mantra. Placing the water challenge at the centre of political and security dialogues, development strategies and climate mitigation and adaptation measures, and implementing smarter water management, could also bring great economic, environmental and social benefits, in and outside the European Union. It would also contribute to global security. Water matters – now more than ever. This is also what this publication demonstrates. Building on the European Policy Centre’s, two-year “Blue Gold” project, this publication shows the rationale for action, how the EU could use its existing internal and external policy instruments to tackle the water challenge with its various dimensions and the benefits of action.