Kinetics of the Hydrogen Oxidation on Pt Modified Moox Nano-Sized Catalyst in the Presence of Carbon Monoxide

Poster presented at the 11th Conference of the Materials Research Society of Serbia - YUCOMAT 2009, Herceg Novi, Montenegro, August 31 – September 4, 2009

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

Kinetics of the hydrogen oxidation on pt modified MoOx nano-sized catalyst in the presence of carbon monoxide

Due to the importance of the HOR in fuel-cells technology, various Pt-based catalysts have been examined from the viewpoint of immunity of the electrocatalysis of the HOR from CO-poisoning of the anode catalysts. An appreciable improvement of the CO tolerance has been found at Pt with adatoms such as Ru, Sn [1,2], Pt-M (M=Ru, Rh, Os, W Sn) [3-5] based alloys, and Pt with oxides (RuOxHy) [6]. In the present work, the electrocatalytic of home made highly dispersed nano-sized MoOx-Pt/C catalysts prepared by the polyole method combined by MoOx post-deposition was investigated in the presence of CO, in 0.5 moldm-3 HClO4 solution. The partial pressure of CO in CO/H2 gas mixture was 100 ppm. Carbon monoxide was adsorbed on the RDE for various time interval with keeping the potential at 0.05 V (RHE). The coverage of CO was determined by applying the first potential sweep (from 0.04 to 1.20 V), in N2 saturated solution at potential scan rate of 0.1 Vs-1 and compared it with the sweep on the clean electrode, by measuring the decrease in the hydrogen desorption charge, ΔQH. MoOx(20%)Pt/C catalyst exhibits an excellent CO tolerance, as it was found that the reduction in kinetic current, Ik, is negligible even at ΘCO = 0.46. It was found for this catalyst too, that the CO adsorption rate was much slower than that of Pt and the Pt sites for HOR were not so rigidly blocked by adsorbed CO partially due to its enhanced mobility, resulting from their modified electronic structure of surface Pt sites. Voltammetric studies suggest that an excellent CO tolerance of this catalyst could be also result of the oxidation of adsorbed CO to CO2 by oxophilic MoOx species at low overpotentials by a redox-mediated mechanism.Poster: [https://hdl.handle.net/21.15107/rcub_dais_266

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

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

Seroprevalencija infekcije izazvane uzročnikom Anaplasma phagocytophilum kod pasa u Autonomnoj Pokrajini Vojvodini, Srbija.

Granulocytic anaplasmosis in dogs is a disease that is distributed worldwide, caused by the pathogen Anaplasma phagocytophilum. This disease is transmitted by ticks of the Ixodes genus. So far, no data have been published about the presence and prevalence of dog infections with A. phagocytophilum in the Autonomous Province of Vojvodina and the Republic of Serbia proper. The aim of this seroepidemiological research was to determine the seroprevalence of IgG antibodies to the agent A. phagocytophilum in the population of dogs in Vojvodina, Serbia. This seroepidemiological research involved 84 randomly selected dogs from the area of the Autonomous Province of Vojvodina. Aiming to determine the presence of antibodies of class G to the agent Anaplasma phagocytophilum, we used the indirect immunofluorescence antibody test (IFAT). By applying IFAT, in the area of the Autonomous Province of Vojvodina, Serbia, specifi antibodies of class G to agent A. phagocytophilum were found in the serums of 13/84 dogs, which points to a seroprevalence of 15.5 %. The detection of antibodies to the agent A. phagocytophilum in the dog population in the area of the Autonomous Province Vojvodina is the basis for further epidemiological, clinical and diagnostic research of this infection.Granulocitna anaplazmoza pasa proširena je diljem svijeta, a prouzročena je vrstom Anaplasma phagocytophilum. Prenosi se krpeljima roda Ixodes. Do sada u Autonomnoj Pokrajini Vojvodini i Republici Srbiji nema objavljenih podataka o prisutnosti i raširenosti infekcije pasa uzročnikom A. phagocytophilum. Cilj je ovoga seroepidemiološkog istraživanja da se utvrdi seroprevalencija IgG protutijela za A. phagocytophilum u populaciji pasa u Vojvodini, Srbija. Ovim seroepidemiološkim istraživanjem, obuhvaćena su 84 nasumično izabrana psa s područja Autonomne Pokrajine Vojvodine. U cilju utvrđivanja prisutnosti protutijela razreda IgG za A. phagocytophilum rabljen je test indirektne imunofl uorescencije (IFAT). Primjenom IFATa, na području Autonomne Pokrajine Vojvodine, Srbija, utvrđena su specifična protutijela IgG na uzročnika A. phagocytophilum u serumu 13 pasa, što predstavlja seroprevalenciju od 15,5 %. Dokaz protutijela za A. phagocytophilum u populaciji pasa na području Autonomne Pokrajine Vojvodine osnova je za daljnja epidemiološka, klinička i dijagnostička istraživanja ove infekcije

Seroprevalencija infekcije izazvane uzročnikom Anaplasma phagocytophilum kod pasa u Autonomnoj Pokrajini Vojvodini, Srbija.

Granulocytic anaplasmosis in dogs is a disease that is distributed worldwide, caused by the pathogen Anaplasma phagocytophilum. This disease is transmitted by ticks of the Ixodes genus. So far, no data have been published about the presence and prevalence of dog infections with A. phagocytophilum in the Autonomous Province of Vojvodina and the Republic of Serbia proper. The aim of this seroepidemiological research was to determine the seroprevalence of IgG antibodies to the agent A. phagocytophilum in the population of dogs in Vojvodina, Serbia. This seroepidemiological research involved 84 randomly selected dogs from the area of the Autonomous Province of Vojvodina. Aiming to determine the presence of antibodies of class G to the agent Anaplasma phagocytophilum, we used the indirect immunofluorescence antibody test (IFAT). By applying IFAT, in the area of the Autonomous Province of Vojvodina, Serbia, specifi antibodies of class G to agent A. phagocytophilum were found in the serums of 13/84 dogs, which points to a seroprevalence of 15.5 %. The detection of antibodies to the agent A. phagocytophilum in the dog population in the area of the Autonomous Province Vojvodina is the basis for further epidemiological, clinical and diagnostic research of this infection.Granulocitna anaplazmoza pasa proširena je diljem svijeta, a prouzročena je vrstom Anaplasma phagocytophilum. Prenosi se krpeljima roda Ixodes. Do sada u Autonomnoj Pokrajini Vojvodini i Republici Srbiji nema objavljenih podataka o prisutnosti i raširenosti infekcije pasa uzročnikom A. phagocytophilum. Cilj je ovoga seroepidemiološkog istraživanja da se utvrdi seroprevalencija IgG protutijela za A. phagocytophilum u populaciji pasa u Vojvodini, Srbija. Ovim seroepidemiološkim istraživanjem, obuhvaćena su 84 nasumično izabrana psa s područja Autonomne Pokrajine Vojvodine. U cilju utvrđivanja prisutnosti protutijela razreda IgG za A. phagocytophilum rabljen je test indirektne imunofl uorescencije (IFAT). Primjenom IFATa, na području Autonomne Pokrajine Vojvodine, Srbija, utvrđena su specifična protutijela IgG na uzročnika A. phagocytophilum u serumu 13 pasa, što predstavlja seroprevalenciju od 15,5 %. Dokaz protutijela za A. phagocytophilum u populaciji pasa na području Autonomne Pokrajine Vojvodine osnova je za daljnja epidemiološka, klinička i dijagnostička istraživanja ove infekcije

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

The occurrence of Trichophytosis among people and cattle on a farm in Vojvodina, Serbia

Dermatophytoses are frequent contagious fungal skin diseases that affect the skin of people and animals. Zoophile dermatophytes pose a significant problem for both human and veterinary medicine, and they are especially present among bovines. In this paper we showed a simultaneous occurrence of trichophytosis among professionally exposed people and bovines on a farm in Vojvodina, Serbia. The tested samples (skin scrapings and hair) originating from people and animals, were positive for Trichophyton verrucosum dermatophyte which was determined by applying a direct microscopic examination of the smears, as well as the isolation and identification of the agents

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