Ordered Mesoporous Carbon as a Support of Pd Catalysts for CO2 Electrochemical Reduction

© 2020 by the authors.Ordered mesoporous carbons (OMCs) have been used as catalyst supports of Pd nanoparticles for the electrochemical reduction of CO2 in 0.1 M KHCO3. OMC with tunable porosity and morphology were obtained by the hard-template approach using synthesized SBA-15 templates. SBA-15 materials were prepared using a mass ratio of the silica precursor (TEOS) and the surfactant (P123) of 2 or 5. After removing silica particles by a purification treatment with NaOH-ethanol or HF, different OMCs were obtained, with a developed porosity (up to 1050 m2 g−1) and ordered 2D hexagonal mesostructure (p6 mm). An increase in the TEOS/P123 ratio as well as the treatment with HF resulted in a decrease in the structural ordering of the materials. Pd nanoparticles with an average size of around 3 nm were deposited on the OMC. However, larger nanoparticles were also observed, especially for the materials obtained using a mass ratio TEOS/P123 of 5. Despite these differences, electrochemical experiments showed that CO2 was successfully reduced to other species (mainly COad) for all Pd/OMC electrocatalysts. These reduced species were adsorbed on Pd active sites, inhibiting the hydrogen evolution reactionThe authors gratefully acknowledge the financial support given to the Fuel Conversion Group by the Aragón Government (T06).Peer reviewe

Spectroelectrochemical study of carbon monoxide and ethanol oxidation on Pt/C, PtSn(3:1)/C and PtSn(1:1)/C catalysts

PtSn-based catalysts are one of the most active materials toward that contribute ethanol oxidation reaction (EOR). In order to gain a better understanding of the Sn influence on the carbon monoxide (principal catalyst poison) and ethanol oxidation reactions in acidic media, a systematic spectroelectrochemical study was carried out. With this end, carbon-supported PtSnx (x = 0, 1/3 and 1) materials were synthesized and employed as anodic catalysts for both reactions. In situ Fourier transform infrared spectroscopy (FTIRS) and differential electrochemical mass spectrometry (DEMS) indicate that Sn diminishes the amount of bridge bonded CO (COB) and greatly improves the CO tolerance of Pt-based catalysts. Regarding the effect of Sn loading on the EOR, it enhances the catalytic activity and decreases the onset potential. FTIRS and DEMS analysis indicate that the C-C bond scission occurs at low overpotentials and at the same potential values regardless of the Sn loading, although the amount of C-C bond breaking decreases with the rise of Sn in the catalytic material. Therefore, the elevated catalytic activity toward the EOR at PtSn-based electrodes is mainly associated with the improved CO tolerance and the incomplete oxidation of ethanol to form acetic acid and acetaldehyde species, causing the formation of a higher amount of both C2 products with the rise of Sn loading.This research was funded by Fundación Cajacanarias (project BIOGRAF) the Spanish Ministry of Economy and Competitiveness (MINECO) under projects CTQ2011-28913-C02 and ENE2014-52158-C02 (co-funded by FEDER). R.R. acknowledges the FPI program (MINECO) for financial support. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI

Catalizadores basados en materiales grafénicos dopados para reacciones catódicas en pilas de combustible y electrolizadores de membrana polimérica

Los materiales grafénicos presentan interesantes propiedades que pueden ser modificadas mediante estrategias de dopado, convirtiendo estos materiales en candidatos para sustituir a los metales nobles en los electrodos de los dispositivos de almacenamiento y conversión de energía (pilas de combustible y electrolizadores). El objetivo de esta Tesis Doctoral es la síntesis y caracterización de electrocatalizadores basados en materiales grafénicos que aúnen una alta actividad electrocatalítica y bajo coste. Se han sintetizado materiales grafénicos dopados con distintos heteroátomos (nitrógeno, boro, fósforo y azufre) a los que se han incorporado metales no nobles (hierro y cobalto). La actividad electrocatalítica hacia la reacción de reducción de oxígeno se ha estudiado utilizando técnicas comunes en celda de tres electrodos y técnicas avanzadas de espectroscopia fotoelectrónica de rayos-X con electroquímica quasi in situ, estudios de estabilidad y en estación de pila de combustible. La actividad hacia la reacción de evolución de hidrógeno se ha estudiado utilizando técnicas clásicas de voltamperometría en celda de tres electrodos y mediante espectrometría de masas diferencial electroquímica (DEMS). La incorporación de heteroátomos y metales no nobles contribuye al aumento de la actividad catalítica para las dos reacciones en estudio.<br /

Gas diffusion electrodes for methanol electro-oxidation studied by a new DEMS configuration: Influence of the diffusion layer

A novel differential electrochemical mass spectrometry (DEMS) cell has been developed to study gas diffusion electrodes (GDEs) used in fuel cells under operating conditions. In this way, catalytic and diffusion properties of the electrodes can be evaluated at the same time. Moreover, DEMS, allows the detection of volatile and gaseous products and intermediates generated in the electrochemical reactions with good sensitivity. In this way, CO2 conversion efficiencies are evaluated during alcohol oxidation reaction. In the present communication, the electrochemical behaviour towards hydrogen evolution and CO and alcohol electrooxidation at different platinum-based catalysts has been studied using the new DEMS cell configuration. The relative yields of CO2 and by-side products during methanol oxidation have been evaluated to determine the CO2 conversion efficiency. In addition, the diffusional properties of diverse GDEs have been considered.This work has been supported by the Gobierno de Aragón and Obra Social LaCaixa under project GA-LC-008/2009 and by the Gobierno de Canarias under project PI2007/023. S. Pérez-Rodríguez also acknowledges Gobierno de Aragón for their DGA grant. G. García acknowledges to the JAE program (CSIC) for financial support.Peer reviewe

Nanoestructuras de carbono nitrogenadas para pilas de combustible de electrolito polimérico.

El reto de la descarbonización de la economía se ha encontrado con un hándicap añadido, como es la pandemia COVID-19, que va a condicionar una agenda ya de por sí comprometida y de difícil gestión para gobiernos, instituciones, empresas e incluso ciudadanos. En cambio, la gestión de esta crisis económica derivada de la alarma sanitaria podría utilizarse como palanca y motor del cambio para introducir con mayor diligencia la tan necesaria transición hacia el empleo de energías limpias y sostenibles en sustitución de los combustibles fósiles en los sectores de transporte y de generación de electricidad. Dentro de este escenario, el hidrógeno es un vector energético limpio y versátil, por lo que su aplicación en pilas de combustible supone una apuesta segura en la industria automovilística, ya que garantiza el objetivo de cero emisiones y presenta mejores prestaciones en términos de autonomía y tiempos de carga. En este contexto, el trabajo principal de esta Tesis Doctoral se ha basado en el estudio de catalizadores para su utilización en pilas de combustible, con el objetivo de reducir la cantidad de metal noble necesaria y, por tanto, la reducción de sus costes, manteniendo un alto rendimiento. Concretamente, la investigación se ha centrado en la modificación con grupos nitrogenados de materiales carbonosos que se utilizan como soporte, para mejorar sus características y analizar cómo influyen en el comportamiento de los catalizadores, buscando así reducir o incluso eliminar la cantidad de metal noble requerida.Para ello, se han sintetizado y caracterizado materiales de carbono de diferente naturaleza como son las nanofibras de carbono, los xerogeles de carbono y los materiales mesoporosos ordenados, y se han comparado con un negro de carbono comercial, Vulcan XC 72R. Se han aplicado diferentes técnicas de modificación con nitrógeno para cada uno de estos materiales, observándose que con aquellas en las que los grupos nitrogenados se introducían durante la síntesis de dichos materiales, se obtenían materiales carbonosos dopados con mayor cantidad de grupos nitrogenados que con los tratamientos de modificación después de la obtención del material. Asimismo, se ha realizado la caracterización fisicoquímica de los materiales carbonosos dopados con nitrógeno y se han estudiado electroquímicamente como catalizadores sin metal para analizar la influencia de los grupos nitrogenados en la reacción de reducción de oxígeno en medio básico. La mejor actividad se ha obtenido para los materiales mesoporosos ordenados dopados con N, que han sido, a su vez, los de mayor contenido en N. Finalmente, los materiales carbonosos con nitrógeno se han utilizado como soporte de catalizadores de Pt y de PtRu para su investigación en las reacciones de reducción de oxígeno y de oxidación de metanol, respectivamente. En este caso, el estudio ha comprendido tanto medio básico como medio ácido. De este modo, se ha analizado la influencia del dopado en la síntesis de dichos catalizadores, en la interacción del soporte-metal, así como en su actividad electroquímica en función del medio de reacción. En cuanto a los catalizadores de Pt, los catalizadores que presentan mayor actividad son los soportados sobre los materiales mesoporosos ordenados dopados con nitrógeno, debido a que los grupos nitrogenados han creado defectos que mejoran la interacción del electrolito con el catalizador. En cambio, en los catalizadores de PtRu, los que han presentado la actividad más elevada son los soportados sobre nanofibras de carbono y Vulcan XC 72R porque son los que se envenenan más lentamente por la formación de especies intermedias de reacción.<br /

Can financial ratios predict the Malaysian stock return?

The purpose of this paper is to use the dividend yield (DY), earning to price ratio (EP), and capital gain (CG) to predict the Malaysia stock market return from 1995 to 2005 by using the time series regression. We utilize both the univariate and multivariate Ordinary Least Square (OLS) regression analysis to test the future monthly and quarterly stock return. We apply the unit root test to test the stationary of the time series, and various diagnostic tests to check for the robustness of model. We find that the financial ratios and the capital gain have a positive relationship with expected monthly and quarterly stock return. Although not all the model show significant relationship between the financial ratios and stock return, it is proven that the financial ratios and capital gain have some predictive power to predict the Malaysia future stock return. From the overall findings, we can suggest that both the univariatre DY with dummy variable and multivariate DY model with dummy variable are the good models to predict the Malaysia monthly and quarterly future nominal stock return

A FTIR characterization of surface interactions of cyanide and coppercyanide with a platinum electrode in alkaline solution

In this paper, the nature of the species formed in the electrochemical interactions between a polycrystalline platinum surface and cyanide and copper-cyanide species in alkaline solution (pH 13) has been investigated by combining cyclic voltammetry with in situ FTIR spectroscopy. This study was performed because electrochemical reactors for the treatment of cyanide-containing industrial wastewaters have been shown to achieve viable destruction rates when copper ions are present in the alkaline solution through the formation of copper oxide films [1-3]. It has been found that the complexation of cyanide ions by copper species hinders the adsorption of the anion at the electrode, thus avoiding the characteristic electrode poisoning by CO that occurs in the absence of soluble copper species. Conversely, soluble copper-cyanide complexes can be electrooxidized at the platinum surface through the formation of cyanate species as intermediate, and of HCOOH and NO as end products. The addition of copper species to the electrolyte also facilitates this route for cyanide oxidation to occur at higher rates without poisoning the platinum electrodeFTIRvoltammetryplatinumcyanide oxidationcopper ionscatalysi

Spectroelectrochemical behavior of polycrystalline gold electrode modified by reverse micelles.

The increasing demand for raising the reliability of electronic contacts has led to the development of methods that protect metal surfaces against atmospheric corrosion agents. This severe problem implies an important economic cost annually but small amounts of corrosion inhibitors can control, decrease or avoid reactions between a metal and its environment. In this regard, surfactant inhibitors have displayed many advantages such as low price, easy fabrication, low toxicity and high inhibition efficiency. For this reason, in this article, the spectroelectrochemical behavior of polycrystalline gold electrode modified by reverse micelles (water/polyethyleneglycol-dodecylether (BRIJ 30)/n-heptane) is investigated by atomic force microscopy (AFM), potentiodynamic methods and electrochemical impedance spectroscopy (EIS). Main results indicate a strong adsorption of a monolayer of micelles on the gold substrate in which electron tunneling conduction is still possible. Therefore, this method of increasing the corrosion resistance of gold contacts is usable only in conditions of long-term storage but not in the operation of devices with such contacts. In this regard, the micelle coating must be removed from the surface of the gold contacts before use. Finally, the aim of the present work is to understand the reactions occurring at the surfactant/metal interface, which may help to improve the fabrication of novel electrodes

Identification of novel risk loci, causal insights, and heritable risk for Parkinson's disease: a meta-analysis of genome-wide association studies

Background Genome-wide association studies (GWAS) in Parkinson's disease have increased the scope of biological knowledge about the disease over the past decade. We aimed to use the largest aggregate of GWAS data to identify novel risk loci and gain further insight into the causes of Parkinson's disease. Methods We did a meta-analysis of 17 datasets from Parkinson's disease GWAS available from European ancestry samples to nominate novel loci for disease risk. These datasets incorporated all available data. We then used these data to estimate heritable risk and develop predictive models of this heritability. We also used large gene expression and methylation resources to examine possible functional consequences as well as tissue, cell type, and biological pathway enrichments for the identified risk factors. Additionally, we examined shared genetic risk between Parkinson's disease and other phenotypes of interest via genetic correlations followed by Mendelian randomisation. Findings Between Oct 1, 2017, and Aug 9, 2018, we analysed 7·8 million single nucleotide polymorphisms in 37 688 cases, 18 618 UK Biobank proxy-cases (ie, individuals who do not have Parkinson's disease but have a first degree relative that does), and 1·4 million controls. We identified 90 independent genome-wide significant risk signals across 78 genomic regions, including 38 novel independent risk signals in 37 loci. These 90 variants explained 16–36% of the heritable risk of Parkinson's disease depending on prevalence. Integrating methylation and expression data within a Mendelian randomisation framework identified putatively associated genes at 70 risk signals underlying GWAS loci for follow-up functional studies. Tissue-specific expression enrichment analyses suggested Parkinson's disease loci were heavily brain-enriched, with specific neuronal cell types being implicated from single cell data. We found significant genetic correlations with brain volumes (false discovery rate-adjusted p=0·0035 for intracranial volume, p=0·024 for putamen volume), smoking status (p=0·024), and educational attainment (p=0·038). Mendelian randomisation between cognitive performance and Parkinson's disease risk showed a robust association (p=8·00 × 10−7). Interpretation These data provide the most comprehensive survey of genetic risk within Parkinson's disease to date, to the best of our knowledge, by revealing many additional Parkinson's disease risk loci, providing a biological context for these risk factors, and showing that a considerable genetic component of this disease remains unidentified. These associations derived from European ancestry datasets will need to be followed-up with more diverse data. Funding The National Institute on Aging at the National Institutes of Health (USA), The Michael J Fox Foundation, and The Parkinson's Foundation (see appendix for full list of funding sources)

Electrochemical behavior of the carbon black Vulcan XC-72R: influence of the surface chemistry

The effect of chemical surface oxidation of the carbon black Vulcan XC-72R on the capacitance, tolerance to corrosion and electrochemical activity toward the hydrogen evolution reaction (HER) has been studied in 0.1 M NaHCO3. Acid treatments with HNO3 or a HNO3H2SO4 mixture resulted in a progressive introduction of oxygen-containing groups which led to a strong increase of the capacitance and a higher tendency to carbon corrosion. In contrast, an inhibition of the hydrogen evolution current (at potentials more negative than −1.0 V) was observed for oxidized samples in comparison to the un-treated material. HER was also tested in the presence of dissolved CO2 to study the influence of the surface chemistry on the CO2 electroreduction. An inhibition of the H2 evolution current was evidenced in the CO2 saturated electrolyte due to the adsorption of species from CO2 reduction. A strong hydrogen current decrease (65–78%), and thus a higher tendency to adsorb (CO2)red species, was obtained on the original Vulcan and the HNO3-treated samples, in comparison to the carbon oxidized with HNO3H2SO4 (15%), which could be related to the highest content of basic groups of the last carbon.The authors gratefully acknowledge financial support given by Spanish MINECO (ENE2014-52158-C2-1-R and 2-R). S. Pérez-Rodríguez thanks Gobierno de Aragón for the DGA grant. Furthermore, the authors wish to acknowledge Dra. Ana Beatriz García for the TPD measurements.Peer reviewe