A novel platinum-based nanocatalyst at a niobia-doped titania support for the hydrogen oxidation reaction

The kinetics of the hydrogen oxidation reaction (HOR) was studied at Pt nanoparticles supported on niobia-doped titania (Pt/N-T). The catalyst support, with the composition of 0.05NbO2.5-δ-0.995TiO2 (0<δ<1), was synthesized by a modified sol-gel procedure and characterized by the BET and X-ray diffraction (XRD) techniques. The specific surface area of the support was found to be 70 m2 g-1. The XRD analysis revealed the presence of the anatase TiO2 phase in the support powder. No peaks indicating the existence of Nb-compounds were detected. Pt/N-T nanocatalyst was synthesized by the borohydride reduction method. Transmission electron microscopy revealed a quite homogenous distribution of the Pt nanoparticles over the support, with a mean particle size of about 3 nm. The electrochemical active surface area of Pt of 42±4 m2 g-1 was determined by the cyclic voltammetry technique. The kinetics of the HOR was investigated by linear sweep voltammetry at a rotating disc electrode in 0.5 mol dm-3 HClO4 solution. The determined value of the Tafel slope of 35 mV dec-1 and an exchange current density of 0.45 mA cm-2 per real surface area of the Pt are in good accordance with those already reported in the literature for the HOR at polycrystalline Pt and Pt nanocatalysts in acid solutions. This new catalyst exhibited better activity for the HOR in comparison with Pt nanocatalyst supported on Vulcan® XC-72R high area carbon

Preparation and Characterization of Pt Nanocatalyst on Tungsten Based Support for Alkaline Fuel Cells Applications

Poster presented at the 13th Annual Conference of the Materials Research Society of Serbia - YUCOMAT 2011, Herceg Novi, Montenegro, September 5–9, 201

CHEMICAL CHARACTERISTICS OF CULTIVATED ELDERBERRY FRUIT

This work is consered with the processing value of Elderberry fruit (berries) from domestic plantation selection (Horgoš region). Chemical analyses of reference parameters confirmed high nutritional and physiological value of samples and full validity of work on this selection and production in plantation conditions

Synthesis and characterization of Pt nanocatalyst on tin oxide based support for oxygen reduction

Platinum nanocatalyst on Sb doped tin oxide support has been synthesized and characterized as a catalyst for oxygen reduction reaction in 0.5 mol dm-3 HClO4 solution, at 25°C. Sb doped tin oxide support has been synthesized by sol-gel procedure. Synthesized support was characterized by BET (Brunauer, Emmett, Teller), X-ray diffraction and cyclic voltammetry techniques. Specific surface area of the support determined from nitrogen adsorption/desorption isothermal curves was 42 m2 g-1. Platinum nanocatalyst at modified tin oxide support has been synthesized by borohydride reduction method and characterized by XRD and TEM techniques. Quite homogenous Pt nanoparticles distribution over the support, without pronounced particle agglomeration was observed. Electrochemically active surface area of the catalyst was determined from adsorption/desorption charge of hydrogen atoms, after double layer charge substraction, taking into account the reference value of 210 μC cm-2 for full coverage with adsorbed hydrogen species. The oxygen reduction reaction at Pt/SbSnO2 catalyst has been studied by cyclic voltammetry and linear sweep voltammetry at rotating disc electrode. Two different Tafel slope were observed: one close to 60 mV dec-1 in low current density region, and other close to 120 mV dec-1 at high current densities region, as it was already reported in literature for oxygen reduction at pure polycrystalline Pt, as well as at Pt nanoparticles in acid solutions. The specific activities, expressed in terms of kinetic current densities per electrochemically active surface area at the constant potential, of this new catalyst and Vulcan supported Pt were compared. Pt/SbSnO2 catalyst exhibited similar catalytic activity for oxygen reduction reaction compared to carbon supported one. Better durability of Pt/SbSnO2 catalyst under repetitive cycling up to 1.4 V vs RHE was confirmed, comparing with Pt on carbon support

Površinska modifikacija platine zlatom i zlata platinom i njen uticaj na reakcije izdvajanja vodonika i redukcije kiseonika

Surface modification of the electrodes was conducted from sulfuric acid solutions containing the corresponding metal-chloride complexes using cyclic voltammeter. Comparing the charges of the hydrogen underpotential deposition region, and the corresponding oxide reduction regions, it is concluded that a platinum overlayer on gold forms 3D islands, while gold on platinum forms 2D islands. Foreign metals present in an amount of up to one monolayer exert an influence on the change in reaction rate with respect to both hydrogen evolution (HER) and oxygen reduction (ORR) reactions. Aplatinum overlayer on a gold substrate increases the activity for HER and for ORR, compared with pure gold. These results can be understood in terms of a simple model, in which the change in the H and OH binding energies are directly proportional to the shift of the d-bond center of the overlayer. On the contrary, a gold layer on platinum slightly decreases the activity for both reactions compared with pure platinum.Površinska modifikacija platine zlatom i zlata platinom je izvršena iz rastvora sumporne kiseline i odgovarajućih hloridnih kompleksa metala primenom ciklične voltametrije. Poređenjem količine naelektrisanja u oblasti potpotencijalne depozicije vodonika i odgovarajućih oblasti redukcije oskida čistih i modifikovanih elektroda zaključeno je da platina na zlatu formira 3D, a zlato na platini 2D ostrva. Aktivnosti ovako modifikovanih površina za reakcije izdvajanja vodonika i redukcije kiseonika u rastvoru sumporne kiseline poređene sa aktivnostima čistih metala. Elektroda od zlata modifikovana platinom značajno uvećava aktivnost za obe ispitivane rekacije u poređenju sa čistim zlatom. Sa druge strane, elektroda od platine modifikovana zlatom ima neznatno manju aktivnost u poređenju sa čistom platinom. Zbog ograničenih resursa i visoke cene platine platina modifikovana zlatom može biti zamena za čistu platinu kao dobar katalizator za reakciju redukcije kiseonika, posebno u gorivim spregovima u oblasti niskih temperatura

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e. a controlling message) compared to no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly-internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared to the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly-internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing: Controlled motivation was associated with more defiance and less long-term behavioral intentions to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

A global experiment on motivating social distancing during the COVID-19 pandemic

Significance Communicating in ways that motivate engagement in social distancing remains a critical global public health priority during the COVID-19 pandemic. This study tested motivational qualities of messages about social distancing (those that promoted choice and agency vs. those that were forceful and shaming) in 25,718 people in 89 countries. The autonomy-supportive message decreased feelings of defying social distancing recommendations relative to the controlling message, and the controlling message increased controlled motivation, a less effective form of motivation, relative to no message. Message type did not impact intentions to socially distance, but people’s existing motivations were related to intentions. Findings were generalizable across a geographically diverse sample and may inform public health communication strategies in this and future global health emergencies. Abstract Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

Adsorption and corrosion inhibitive properties of some organic molecules on iron electrode in sulfuric acid

Adsorption and corrosion inhibitive properties of three different organic molecules: 2-naphthalenesulfonic acid, 2,7-naphthalenedisulfonic acid and 2-naphthol-3,6-disulfonic acid are investigated on Armco-iron electrode cathodically polarized, in 0.5 mol dm -3 H 2 SO 4 solution. The examinations show that the three organic molecules behave as a cathodic corrosion inhibitors. The inhibitive efficiency, changes with the number of functional groups substituted on benzene ring and increases with concentration. The experimentally obtained adsorption isoterms follow the Frumkin equation [0/n(1-0) n ] exp(-2aθ) = Bc and the best fit is obtained for n = 2 (for 2-NSA) and n = 3 (for 2,7-NDSA and 2N-3,6-DSA). The calculated values for the parameter a are 2.1-2.9 and Gibbs energies are 17-21 kJ mol -1 . The adsorption rate constants are very small, proving that iron surface permanently changes due to the corrosion processes