What Controls Activity Trends of Electrocatalytic Hydrogen Evolution Reaction?-Activation Energy Versus Frequency Factor

Renewable energy storage via water electrolysis strongly depends on the design of electrified electrode–electrolyte interfaces at which electricity is converted into chemical energy. At the core of the hydrogen evolution reaction (HER) and the oxygen evolution reaction conversion efficiency are interfacial processes with complex dynamic mechanisms, whose further acceleration is practically impossible without a thorough fundamental understanding of electrocatalysis. Here, we communicate new experimental insights into HER, which will potentially further deepen our general understanding of electrocatalysis. Of special note is the very surprising observation that the most active metals (i.e., noble metals) for HER, which exhibit the lowest overpotentials at a defined current density, exhibit the highest activation energies in comparison to the other metals from the d-block. This suggests a major, if not dominant, impact of the frequency factor on activity trends and the need for deeper reconsideration of the origins of electrocatalytic activity

The Effect of Iron Impurities on Transition Metal Catalysts for the Oxygen Evolution Reaction in Alkaline Environment: Activity Mediators or Active Sites?

There is an ongoing debate on elucidating the actual role of Fe impurities in alkaline water electrolysis, acting either as reactivity mediators or as co-catalysts through synergistic interaction with the main catalyst material. This perspective summarizes the most prominent oxygen evolution reaction (OER) mechanisms mostly for Ni-based oxides as model transition metal catalysts and highlights the effect of Fe incorporation on the catalyst surface in the form of impurities originating from the electrolyte or co-precipitated in the catalyst lattice, in modulating the OER reaction kinetics, mechanism and stabilit

Study of the genetic homogeneity of Albarino (Vitis vinifera L.) growing in Galicia (Spain) using isozyme and RAPD markers

Research NoteAn evaluation of the genetic diversity of cv. Albarino (Vitis vinifera L.) was carried out. Centenarian and young plants were selected from vineyards, some of them showing slight ampelographic differences. Using ELISA tests 5 out of 24 plants were found to be infected with grapevine leafroll-associated virus 3 (GLRaV-3). In order to evaluate genetic polymorphism, 10 enzyme systems and 42 RAPD primers were used. The 73 isozyme and 308 RAPD markers were common in the samples tested. The results show the existence of a genetic homogeneity within Albarino cultivated in Galicia. Minor ampelographic differences among samples could be due to external factors rather than to genetic differences

Influence of elevation and slope exposure on must volatiles of mencía cultivar from Ribeira Sacra (NW Spain)

Ribeira Sacra is a Spanish Denomination of Origen (D.O.) that produces young red wines from Mencía cultivar (Galicia, NW). The orography of the Ribeira Sacra D.O. is very characteristic and renders a wide variety of situations that combine elevation, orientation, slope exposure and slope inclination. Indeed, in this area all have terraced vineyards are very close to just one meter wide, where it is only a single row of vines and spread over the slopes which normally have a large inclination (70 to 80 ° slope). With a south-southwest direction, the vineyards are protected from cold winds from the north and the sun bathes the terraces throughout the day. The stone warmed by the sun during the day blunted the lower night temperatures avoiding frost. During the year 2009 we have studied the volatile composition of Mencía cultivar in six different situations (orientation and altitude) of Amandi subzone (Ribeira Sacra D.O.) and the relationship with the altitude and exposition. The results showed the influence climatic and topographic conditions on the volatile composition of Mencía grape grown along Amandi site from Ribeira Sacra D.O. Six different situations were studied and the data were analysed by analysis of variance and mean differences between situations were calculated using the LSD Fishers’ test. Biplot principal component analysis (PCA) was performed with mean of volatile compounds identified and quantified. The results showed significant differences among the different situations studied, showed different ripening states in the vineyard

Electrocatalysis Beyond 2020: How to Tune the Preexponential Frequency Factor

After a century of research on electrocatalytic reactions, a universal theory of electrocatalysis is still not established due to limited understanding of complex energy conversion processes at electrified electrode-electrolyte interfaces. Most of the research efforts directed toward the acceleration of important electrocatalytic reactions (e. g. hydrogen evolution reaction) were in the direction of minimizing activation energy by tuning the adsorption energies of key intermediates. This kind of approach is well-established and, importantly, in some cases it was valuable by predicting the design of electrocatalysts with advanced properties. However, in some very important research endeavors, advancement in performance of newly designed electrocatalysts could not be attributed to altered/minimized activation energy. Important to note is that modern electrocatalysis almost completely disregards influence of the preexponential factor on reaction rate. In this work, we open some important questions relevant for future of electrocatalysis and electrochemical energy conversion, with special focus on preexponential factor as major contributor to electrocatalytic reaction rate

The Impact of Household Possessions on Youth\u27s Academic Achievement in the Ghana YouthSave Experiment

Households play an important role in youth’s academic achievement. Household assets as part of youth’s family background have been found to have a significant impact on youth’s academic achievement. In this study, the impact of household possessions on youth’s academic achievement in the Ghana YouthSave experiment is investigated. Findings support the hypothesized positive direction of the impact of household possessions on academic achievement of youth. Using propensity score optimal matching and matching estimators, results show youth from households that reported owning at least one of the five household items measured scored almost 1 unit higher on English than their peers from households that do not own any. However, results indicate ownership of household possessions do not have a statistically significant impact on Math scores of youth in the Ghana YouthSave experiment. Although the impact of ownership of household possessions on English scores is consistent across different tests used in this study, the impact of ownership of household possessions on Math scores is less conclusive. Policy implications are discussed

Cellulosomics, a gene-centric approach to investigating the intraspecific diversity and adaptation of Ruminococcus flavefaciens within the rumen

Peer reviewedPublisher PD

A new strategy to design SIW-fed arrays

In this work, a new full-wave strategy, with very low iteration times, is proposed for the optimization and design of antenna arrays fed by substrate integrated waveguides. The device is decomposed into fixed and modifiable (to be optimized) sections, whose generalized scattering matrices are precomputed. The response of the array is calculated by considering firstly only the interactions between the fixed sections, which are then coupled to the modifiable ones in each iteration of an optimization process. To validate the proposed strategy, a transversal 16-slot antenna array, placed on the top plate of a substrate integrated waveguide, has been designed. A speed-up factor of over 2000 times, compared to general purpose commercial software, has been obtained in this optimization process. The final design presents a 1.05 GHz bandwidth under - 10 dB in terms of |S11|, a maximum realized gain of 17.5 dBi at 17 GHz, and a 99.95% maximum efficiency (without dielectric and conductor losses). Index Terms—Addition theorems, cylindrical modes, spherical modes, optimization process, antenna array, substrate integrated waveguide (SIW)

La variedad Albariño en el Valle del Salnés (D.O. Rias Baixas)

El Valle del Salnés es la subzona de la D.O. Rías Baixas con más del 50% de la superficie vitícola de la D.O.. Dentro de las variedades de uva cultivadas en esta D.O., la Albariño (Vitis vinifera L.) se destaca como la más representativa, suponiendo un 95% de la producción total (Consello Regulador D.O. Rías Baixas, datos cosecha 2009). En el presente trabajo, se realizó una caracterización aromática de la uva Albariño producida en el Valle del Salnés en la cosecha 2009