Cost effective alloys based catalysts for alkaline fuel cells application

Alkaline fuel cells (AFCs) have recently become attractive as environmental friendly future power sources. It was really important having in mind that in alkaline media less expensive non noble catalysts could be used. Namely, successful alkaline anion exchange membrane development enabled benefits of faster kinetics of oxygen reduction reaction in alkaline solutions. In this study electrodeposited silver-palladium alloys of various composition were investigated and tested as the prospective catalysts for direct ethanol fuel cells application. All samples were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, as well as by electrochemical techniques: cyclic voltammetry, polarization measurements at rotating disc electrode. The electrochemical active surface area was determined from the charge values corresponding to the reduction of Pd (II) oxide, assuming 420 μC for full oxide monolayer coverage. The optimal alloy composition showing the best catalytic activity for oxygen reduction and ethanol oxidation, with as much as possible lower content of Pd, was determined. It was found that it could be possible to obtain alloys containing only ~ 20% of more noble metal – palladium, showing high activity for both anode and cathode reaction. The stability testing gave very promising results, as well

Accelerated service life test of electrodeposited NiSn coatings as bifunctional hydrogen and oxygen evolution catalysts for alkaline water electrolysis

Electrodeposited NiSn alloy coatings were tested for application as cathodes and anodes in the cell for alkaline water electrolysis in 30 wt.% KOH at 80 ºC. The "accelerated service life test" (ASLT) was performed for HER and OER reactions, and compared to those for Ni electrode. The morphology and chemical compositions of the NiSn and Ni coatings were investigated by SEM and EDS, while their surface composition was investigated by XPS before and after the ASLT for both reactions, respectively. It was shown that the cell voltage at j = 0.3 A cm-2 saving with the NiSn electrodes amounts to about 435 mV before and about 304 mV after the ASLT. SEM results showed that no changes in the morphology of as prepared samples could be detected after the ASLTs for both reactions. EDS and XPS analysis confirmed that some changes occurred during the ASLT, particularly for the oxygen content in the surface layer. This work was financially supported by Ministry of Education, Science and Technological Development Republic of Serbia, under Contract No. 172054. he authors would like to acknowledge networking support by the COST Action MP1407

Comparative study on noble metal based nanocatalysts on different supports for low temperature fuel cells application

Platinum based nanostructures on carbon support are state of the art materials for proton exchange membrane fuel cells application. Contemporary research directions in this field imply synthesis and characterization of novel carbon free catalysts supports to overcome disadvantages of carbon supported ones. We have recently synthesized platinum and palladium nanocatalysts onto different novel metal oxide based supports: titanium-oxide, tin oxide and tungsten oxide, doped by different metals (Nb, Ru, Sb), to achieve satisfactory conductivity. These novel nanostructures were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), as well as by electrochemical techniques. The synthesized nanostructured catalysts were tested for oxygen reduction reaction. Obtained catalytic activities and stabilities were compared to the same noble metal loading catalysts on Vulcan XC-72 support. The results of comparison revealed many advantages of carbon free supported nanocatalysts, regarding both activity and stability

Synthesis and characterization of Pd nanocatalyst at tungsten carbide based support for fuel cells application

Tungsten carbide was prepared by polycondensation of resorcinol and formaldehyde in the presence cetyltrimethylammonium bromide (CTABr) surfactant. Pd nanocatalyst at this support was synthesized by borohydride reduction method. The obtained materials were characterized by XRD, HRTEM, EELS, XPS and electrochemical measurements. TEM analysis revealed Pd nanoparticles size in the range of a few nanometers, even the clusters of Pd atoms. X-Ray Photoelectron Spectroscopy was applied to determine surface composition of the substrates. The presence of palladium based species was revealed. The catalytic activity for the hydrogen oxidation reaction and oxygen reduction were investigated in 0.5 M HClO4 by cyclic voltammetry and linear sweep voltammetry at the rotating disc electrode. The catalysts’ activities were compared to the carbon supported Pd nanoparticles (Vulcan XC 72). WC supported Pd nanoparticles have shown higher CO tolerance, compared even to Pt based catalyst. Acknowledgements: This work was financially supported by Ministry of Education, Science and Technological Development, Republic of Serbia, contract No. 172054.The authors would like to acknowledge networking support by the COST Action MP1407

Synthesis and characterization of Pd nanocatalyst at tungsten carbide based support for fuel cells application

Tungsten carbide was prepared by polycondensation of resorcinol and formaldehyde in the presence cetyltrimethylammonium bromide (CTABr) surfactant. Pd nanocatalyst at this support was synthesized by borohydride reduction method. The obtained materials were characterized by XRD, HRTEM, EELS, XPS and electrochemical measurements. TEM analysis revealed Pd nanoparticles size in the range of a few nanometers, even the clusters of Pd atoms. X-Ray Photoelectron Spectroscopy was applied to determine surface composition of the substrates. The presence of palladium based species was revealed. The catalytic activity for the hydrogen oxidation reaction and oxygen reduction were investigated in 0.5 M HClO4 by cyclic voltammetry and linear sweep voltammetry at the rotating disc electrode. The catalysts’ activities were compared to the carbon supported Pd nanoparticles (Vulcan XC 72). WC supported Pd nanoparticles have shown higher CO tolerance, compared even to Pt based catalyst. Acknowledgements: This work was financially supported by Ministry of Education, Science and Technological Development, Republic of Serbia, contract No. 172054. The authors would like to acknowledge networking support by the COST Action MP1407

Synthesis and characterization of Pd nanocatalyst at tungsten carbide based support for fuel cells application

Tungsten carbide was prepared by polycondensation of resorcinol and formaldehyde in the presence cetyltrimethylammonium bromide (CTABr) surfactant. Pd nanocatalyst at this support was synthesized by borohydride reduction method. The obtained materials were characterized by XRD, HRTEM, EELS, XPS and electrochemical measurements. TEM analysis revealed Pd nanoparticles size in the range of a few nanometers, even the clusters of Pd atoms. X-Ray Photoelectron Spectroscopy was applied to determine surface composition of the substrates. The presence of palladium based species was revealed. The catalytic activity for the hydrogen oxidation reaction and oxygen reduction were investigated in 0.5 M HClO4 by cyclic voltammetry and linear sweep voltammetry at the rotating disc electrode. The catalysts’ activities were compared to the carbon supported Pd nanoparticles (Vulcan XC 72). WC supported Pd nanoparticles have shown higher CO tolerance, compared even to Pt based catalyst. Acknowledgements: This work was financially supported by Ministry of Education, Science and Technological Development, Republic of Serbia, contract No. 172054.The authors would like to acknowledge networking support by the COST Action MP1407

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements