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To obtain highly efficient yet easily produced water-splitting cathodes, Ni-MoO2 composite coatings were electrodeposited at a Ni foam substrate with an open-pore structure, pore size of 450 µm, in a Watts-type bath. The concentration of MoO2 particles (about 100 nm) was varied, while the intensive mixing of the solution was provided by air bubbling with 0.5 L min−1. Electrodeposition was performed at different constant current densities at room temperature. The morphology and composition of the coatings were investigated by SEM and EDS. The hydrogen evolution reaction (HER) was tested in KOH of different concentrations, at several temperatures, in a three-electrode H-cell by recording polarization curves and EIS measurements. The lowest achieved HER overpotential was −158 mV at −0.5 A cm−2. Up-scaled samples, 3 × 3.3 cm2, were tested in a single zero-gap cell showing decreasing cell voltage (from 2.18 V to 2.11 V) at 0.5 A cm−2 over 5 h in 30% KOH at 70 °C with electrolyte flow rate of 58 mL min−1. Compared to pure Ni foams used as both cathode and anode under the same conditions, the cell voltage is decreased by 200 mV, showing improved electrode performance.

This study investigates the structure, electrochemical behavior and hydrogen evolution reaction (HER) performance of electrodeposited Ru–Co alloy coatings. The alloys were prepared from a 0.75 M Co2+ + 0.025 M Ru3+ solution at various potentials ranging from −0.5 to −1.2 V vs. SCE. Results reveal that the Ru and Co deposition processes are interdependent. The deposition of nobler Ru from the mixed metal solution reaches pure diffusion control already at −0.7 V compared to −1.0 V from a single Ru bath. On the other hand, Co deposition is significantly facilitated in the presence of Ru in the solution. Consequently, as the deposition potential changes from −0.6 to −1.0 V, Ru–Co solid solution coatings characterized by a distinct globular morphology are formed, with their Co content increasing from 22.1/7.4 to 70.2/86.1 wt% for the Cu/Ti2AlC MAX phase substrate applied. The alloy catalysts are found to show much better HER activity and stability in alkaline than in acidic solutions. The best Ru–Co@Ti2AlC sample, electrodeposited at −0.6 V, requires an overpotential of only −95 mV to deliver a current density of −100 mA cm−2 in 1 M KOH, thus outperforming most Ru–Co-based HER electrocatalysts reported to date.

Catalytic activity towards the oxygen reduction reaction (ORR) in 0.5 M H2SO4 was investigated at sub-monolayers and ultra-thin layers (corresponding to 10, 30 and 100 monolayers, (MLs)) of Pt electrochemically deposited on (Nb-Ti)2AlC substrate. Electrochemical deposition of Pt layers on (Nb-Ti)2AlC substrate was achieved from the solution containing 3 mM K2PtCl4 + 0.5 M NaCl (pH 4) under the conditions of convective diffusion (RPM = 400) using linear sweep voltammetry (LSV) at a sweep rate of 2 mV s-1, by determining limiting potential for deposition of each Pt sample from the QPt vs. E curves. The Pt samples were characterized X-ray photoelectron spectroscopy (XPS). XPS analysis showed that practically the whole surface of (Nb-Ti)2AlC substrate is covered with homogeneous layer of Pt, while Pt ion reduction was complete to metallic form – Pt(0) valence state. Then oxygen reduction was studied at rotating disc electrode by cyclic voltammetry and linear sweep voltammetry. Two different Tafel slopes were observed, one close to 60 mV dec-1 in low current densities region and second one ~ 120 mV dec-1 in high current densities region. This novel catalyst exhibited higher activity in comparison to carbon supported one, in terms of mass activity – kinetic current density normalized to Pt loading., Ispitivana je reakcija redukcije kiseonika na tankim slojevima platine u 0.5 mol dm-3 H2SO4. Tanki slojevi platine – čija količina naelektrisanja odgovara 10, 30 i 100 teorijskih monoslojeva Pt su istaloženi na nosaču od (Nb-Ti)2AlC. Za elektrohemijsko taloženje je korišćen rastvor 3 mM K2PtCl4 + 0.5 M NaCl pH = 4, u uslovima konvektivne difuzije (RPM = 400) primenom metode linearne skenirajuće voltametrije (LSV) pri brzini promene potencijala od 2 mV s-1 . Elektrohemijski dobijeni platinski katalizatori na pomenutom nosaču su okarakterisani metodom fotoelektronske spektroskopija X-zraka (XPS), kao i elektrohemijskim tehnikama. Za određivanje realne elektrohemijski aktivne površine elektrode je primenjena ciklična voltametrija, integracijom ispod anodnog dela voltamograma u oblasti adsorpcije vodonika na potpotencijalima. Za ispitivanje kinetike reakcije redukcije kiseonika je korišćena metoda linearne skenirajuće voltametrije na rotirajućoj disk elektrodi. Dobijene su dve vrednosti Tafelovog nagiba, jedna približno 60 mV dek-1 u oblasti malih prenapetosti, a druga ~ 120 mV dek-1 , u oblasti većih gustina struje. Katalitička aktivnost katalizatora je poređena sa vrednostima iz literature dobijenim na platini na ugljeničim nosačima na 0.85 V prema reverzibilnoj vodoničnoj elektrodi, izražena kao kinetička gustina struje po realnoj površini electrode, ili specifična aktivnost – izražena kao kinetička gustina struje po masi platine. Pokazano je da katalizator sa 10 monoslojeva platine poseduje veoma dobru katalitičku aktivnost, posebno izraženu po masi istaložene platine.

Two types of iridium oxide films formed at the Ti-2 AlC substrate were investigated: (1) anodically electrodeposited iridium oxide film from the solution based on IrCl(3)xH(2)O; (2) iridium oxide film prepared by cycling thin layer of electrodeposited Ir in the 0.5 M H2SO4 from - 0.25 to 1.20 V. It was shown that during anodic electrodeposition of iridium oxide film (1) coulombic efficiency decreases with increasing anodic potential, being only 3% atE = 0.7 V vs. SCE and 26% atE = 0.62 V vs. SCE. A pair of peaks corresponding to the transition Ir(III)-oxide/Ir(IV)-oxide was present on the CVs recorded in 0.5 M H2SO4. While cycling pure Ir thin layer in the solution of 0.5 M H2SO4 from - 0.25 to 1.20 V (2) up to 100 cycles, typical CV response was characterized with the prepeak and a pair of peaks corresponding to the Ir(III)/Ir(IV)-oxide transition. With the increase of cycles number to 150, additional peak at potential of 1.0 V appeared. This peak was formed on the account of pair of peaks corresponding to the Ir(III)/Ir(IV)-oxide transition. The oxygen evolution reaction (OER) was investigated at both iridium oxide films. It was shown that the Tafel slope for the OER was similar to 40 mV dec(-1)for the first polarization curve, confirming that the rds was a reaction S-OH - gt S-O-ads + H++ e(-). As the number of recorded polarization curves increased, the activity of both types of iridium oxide films decreased, due to dissolution of iridium oxide films at the potentials of the OER. It is shown that anodically electrodeposited iridium oxide film is more active for the OER than that obtained by cycling electrodeposited iridium layer. However, both iridium oxide films exhibited insufficient stability.

The hydrogen evolution reaction (HER) was investigated at sub-monolayers of iridium electrodeposited on Ti2AlC substrate. The lowest amount of electrodeposited iridium was 3 close-packed (111) monolayers (3 ML), while the highest one was 22 ML (3, 5, 10, 15 and 22 ML). The lowest and the highest amounts of iridium were electrodeposited by linear sweep voltammetry (LSV), while the other three samples were electrodeposited by controlled potential coulometry, from the solution containing 1 mM, or 3 mM K3IrCl6 + 0.5 M Na2SO4 (pH 6.2) at 70 °C. The HER was investigated by polarization and electrochemical impedance spectroscopy (EIS) measurements. Polarization curves for iridium sub-monolayers equal, or higher than 6 ML showed low Tafel slope of -14 to -16 mV dec-1 up to about -0.1 A cm-2, while at higher current densities the Tafel slopes increased, varying between -40 and -72 mV dec-1. The highest value of exchange current density (jo) was obtained for 6 ML of electrodeposited iridium, being -27.89 A g-1. The overpotential at j = -0.3 A cm-2 could be determined for samples containing 15 ML and 22 ML of iridium, being 82 mV., Izdvajanje vodonika ispitivano je u rastvoru sumporne kiseline na elektrohemijski istaloženim slojevima (od 3 monosloja do 22 monosloja) iridijuma na podlozi od Ti2AlC. Najmanja i najveća količina iridijuma (3 i 22 monosloja) elektrohemijski su istaložene metodom linearne voltametrije, dok su preostala tri uzorka (6, 10 i 15 monoslojeva) elektrohemijski istaložena pri konstantnom potencijalu do potrebne količine naelektrisanja iz rastvora 1 mM, ili 3 mM K3IrCl6 + 0.5 M Na2SO4 (pH 6.2) na temperaturi rastvora od 70 °C. Reakcija izdvajanja vodonika ispitivana je na svim elektrodama snimanjem polarizacionih krivih. Za uzorak sa 22 monosloja Ir primenjena je i metoda impedanse. Polarizacione krive za uzorke sa 6, 10, 15 i 22 monosloja Ir bile su okarakterisane malom vrednošću Tafel-ovog nagiba od -14 to -16 mV dek-1 u oblasti gustina struja do -0.1 A cm-2, dok se Tafel-ov nagib povećavao pri većim gustinama struja varirajući od -40 do -72 mV dek-1. Najveća vrednost specifične gustine struje izmene (jo) dobijena je kod uzorka sa 6 monoslojeva Ir i iznosila je - 27.89 A g-1. Za uzorke sa 15 i 22 monosloja Ir vrednost prenapetosti pri gustini struje j = -0.3 A cm-2 (uslovi industrijske proizvodnje vodonika) iznosila je 82 mV.

Pronalazak novih materijala koji bi omogućili komercijalizaciju gorivnih spregova i doprineli smanjenju upotrebe fosilnih goriva u proizvodnji energije je od velikog značaja za razvoj savremenog društva. Zbog toga je broj naučnih radova posvećen ovom problemu u značajnom porastu tokom proteklih godina. Kada je u pitanju oksidacija malih organskih molekula kao potencijalnih goriva za gorivni spreg, pored problema visoke cene platine koja se koristi kao katalizator, prisutan je i problem trovanja površine platine ugljen-monoksidom koji se formira kao intermedijar anodne reakcije. U ovom radu nanočestice platine na ugljeničnom nosaču sintetizovane su mikroemulzionim postupkom. Dodatkom različitih količina aditiva HCl tokom sinteze (od 0 do 35 %) ispitan je uticaj dodatka aditiva na oblik nanočestica. Pri optimalnoj koncentraciji od 25% HCl sintetizovane su nanočestice kubnog oblika. Četiri sintetizovana katalizatora okarakterisana su termogravimetrijskom analizom (TGA), rendgenskom difrakcijom X-zraka (XRD), transmisionom elektronskom mikroskopijom (TEM) i transmisionom elektronskom mikroskopijom visoke rezolucije (HRTEM). Ovim metodama potvrđena je promena oblika nanočestica izazvana dodatkom aditiva, utvrđen je udeo metala u katalizatoru (20%) i određena je veličina čestica, koja raste sa porastom udela aditiva (od 4 do 8 nm prema TEM analizi). Elektrohemijskom karakterizacijom i ispitivanjem reakcija oksidacije mravlje kiseline i metanola na ovim katalizatorima, ustanovljeno je da katalizator sa nanočesticama kubnog oblika, i većim udelom preferencijalno orijentisanih ravni (100) pokazuje bolju aktivnost za ove reakcije od katalizatora Pt sa konvencionalnim kub-oktaedarskim česticama. Razlog tome leži u lakšem uklanjanju adsorbovanog CO sa površine nanočestica sa zastupljenim kubnim oblikom., Development of novel materials that would enable the commercialization of fuel cell technology and contribute to reduction of fossil fuel usage in energy production is of great importance for the progress of modern society. As a result, the number of scientific papers devoted to this problem is in a significant increase over the past years. When it comes to the oxidation of small organic molecules (SOM) as potential fuel for the fuel cells, in addition to the problem of the high price of platinum used as a catalyst, there is a problem of poisoning the platinum surface by carbon-monoxide formed as an intermediate in the anodic reaction. In this research carbon supported platinum nanoparticles were synthesized by a water-in-oil microemulsion synthesis procedure. The effect of HCl as a capping agent on nanoparticle shape was investigated by adding up to 35 % HCl in the water phase of the microemulsion. The optimal HCl amount was found to be 25%, in which case platinum was synthesized in the form of cubic-shaped nanoparticles. Four prepared catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and (high resolution) transmission electron microscopy (HR)TEM. These analyses confirmed the change in particle shape induced by the capping agent. Metal loading in catalyst powder was determined to be close to 20%, and the particle size calculated from TEM data went from 4 to 8 nm, with the increase of the HCl amount used. The electrochemical characterization and the investigation of these samples in the reactions of formic acid and methanol oxidation revealed improved catalytic performance of the sample that predominantly contained cubic-shaped nanoparticles compared to conventional cube-octahedron shaped particles. The reason of the improved activity and stability of this catalyst lies in the facilitated CO removal from the catalyst surface, and thus improved tolerance to surface poisoning.

Low loading PtAu nanoparticles supported on high area carbon were synthesized by water-in-oil microemulsion method and examined for formic acid and methanol oxidation. Prepared catalyst powder was characterized by Xray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). These techniques revealed that the catalyst contains rather agglomerated quasi-spherical particles, similar to 4 nm diameter, composed of a solid solution of Pt and Au with only similar to 4 at% of Au. In spite of such low Au content, both onset and peak potentials for CO oxidation are shifted some 150 mV to more positive values in comparison to Pt synthesized in the same manner due to stronger binding of CO as a result of notable electronic effect. It is important that this small quantity of Au also significantly influences oxidation of formic acid promoting direct path and suppressing indirect path in formic acid oxidation in a degree as expected by a much larger quantity of Au. Such improvement could be due exclusively by ensemble effect of high number of small Pt domains which formation could be possible only by very fine dispersion of such low Au quantity. High number of small Pt domains is corroborated by lower activity for methanol oxidation in comparison to Pt catalyst synthesized by the same procedure. These results emphasize the importance of the Au dispersion on the surface of Pt over its quantity in PtAu catalyst with regards to both, the ensemble and the electronic effects.

Development of novel materials that would enable the commercialization of fuel cell technology and contribute to reduction of fossil fuel usage in energy production is of great importance for the progress of modern society. As a result, the number of scientific papers devoted to this problem is in a significant increase over the past years. When it comes to the oxidation of small organic molecules (SOM) as potential fuel for the fuel cells, in addition to the problem of the high price of platinum used as a catalyst, there is a problem of poisoning the platinum surface by carbon-monoxide formed as an intermediate in the anodic reaction. In this research carbon supported platinum nanoparticles were synthesized by a water-in-oil microemulsion synthesis procedure. The effect of HCl as a capping agent on nanoparticle shape was investigated by adding up to 35 % HCl in the water phase of the microemulsion. The optimal HCl amount was found to be 25%, in which case platinum was synthesized in the form of cubic-shaped nanoparticles. Four prepared catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and (high resolution) transmission electron microscopy (HR)TEM. These analyses confirmed the change in particle shape induced by the capping agent. Metal loading in catalyst powder was determined to be close to 20%, and the particle size calculated from TEM data went from 4 to 8 nm, with the increase of the HCl amount used. The electrochemical characterization and the investigation of these samples in the reactions of formic acid and methanol oxidation revealed improved catalytic performance of the sample that predominantly contained cubic-shaped nanoparticles compared to conventional cube-octahedron shaped particles. The reason of the improved activity and stability of this catalyst lies in the facilitated CO removal from the catalyst surface, and thus improved tolerance to surface poisoning., Pronalazak novih materijala koji bi omogućili komercijalizaciju gorivnih spregova i doprineli smanjenju upotrebe fosilnih goriva u proizvodnji energije je od velikog značaja za razvoj savremenog društva. Zbog toga je broj naučnih radova posvećen ovom problemu u značajnom porastu tokom proteklih godina. Kada je u pitanju oksidacija malih organskih molekula kao potencijalnih goriva za gorivni spreg, pored problema visoke cene platine koja se koristi kao katalizator, prisutan je i problem trovanja površine platine ugljen-monoksidom koji se formira kao intermedijar anodne reakcije. U ovom radu nanočestice platine na ugljeničnom nosaču sintetizovane su mikroemulzionim postupkom. Dodatkom različitih količina aditiva HCl tokom sinteze (od 0 do 35 %) ispitan je uticaj dodatka aditiva na oblik nanočestica. Pri optimalnoj koncentraciji od 25% HCl sintetizovane su nanočestice kubnog oblika. Četiri sintetizovana katalizatora okarakterisana su termogravimetrijskom analizom (TGA), rendgenskom difrakcijom X-zraka (XRD), transmisionom elektronskom mikroskopijom (TEM) i transmisionom elektronskom mikroskopijom visoke rezolucije (HRTEM). Ovim metodama potvrđena je promena oblika nanočestica izazvana dodatkom aditiva, utvrđen je udeo metala u katalizatoru (20%) i određena je veličina čestica, koja raste sa porastom udela aditiva (od 4 do 8 nm prema TEM analizi). Elektrohemijskom karakterizacijom i ispitivanjem reakcija oksidacije mravlje kiseline i metanola na ovim katalizatorima, ustanovljeno je da katalizator sa nanočesticama kubnog oblika, i većim udelom preferencijalno orijentisanih ravni (100) pokazuje bolju aktivnost za ove reakcije od katalizatora Pt sa konvencionalnim kub-oktaedarskim česticama. Razlog tome leži u lakšem uklanjanju adsorbovanog CO sa površine nanočestica sa zastupljenim kubnim oblikom.

Low loading PtAu nanoparticles supported on high area carbon were synthesized by water-in-oil microemulsion method and examined for formic acid and methanol oxidation. Prepared catalyst powder was characterized by Xray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). These techniques revealed that the catalyst contains rather agglomerated quasi-spherical particles, similar to 4 nm diameter, composed of a solid solution of Pt and Au with only similar to 4 at% of Au. In spite of such low Au content, both onset and peak potentials for CO oxidation are shifted some 150 mV to more positive values in comparison to Pt synthesized in the same manner due to stronger binding of CO as a result of notable electronic effect. It is important that this small quantity of Au also significantly influences oxidation of formic acid promoting direct path and suppressing indirect path in formic acid oxidation in a degree as expected by a much larger quantity of Au. Such improvement could be due exclusively by ensemble effect of high number of small Pt domains which formation could be possible only by very fine dispersion of such low Au quantity. High number of small Pt domains is corroborated by lower activity for methanol oxidation in comparison to Pt catalyst synthesized by the same procedure. These results emphasize the importance of the Au dispersion on the surface of Pt over its quantity in PtAu catalyst with regards to both, the ensemble and the electronic effects.

Sve veće potrebe za proizvodnjom energije iz obovljivih izvora, uslovile su intenzivna istraživanja u pravcu korišćenja ekološki prihvatljivih goriva. Oksidacijom vodonika u gorivnim spregovima postiže se proizvodnja energije na ekološki prihvatljiv način, a umesto vodonika mogu se koristiti i mali organski molekuli, poput mravlje kiseline koji su bezbedniji za upotrebu i transport. Njihova oksidacija u anodnom delu polimer elektrolitnog gorivnog sprega zahteva upotrebu plemenitih metala kao katalizatora, jer mogu da omoguće njihovu dehidrogenaciju kao početni stupanj reakcije. Kao do sada najbolji katalizatori za oksidaciju mravlje kiseline pokazali su se bimetalni PtAu katalizatori, zahvaljujući geometrijskom efektu zlata na platinu kojim se favorizuje direktni mehanizam oksidacije i izbegava stvaranje reakcionog intermedijara CO koji se ponaša kao katalitički otrov. U ovom radu PtAu katalizatori na aktiviranom ugljeniku sintetizovani su mikroemulzionim postupkom, sa uticajem aditiva kojim je izmenjen oblik čestica, čime je dodatno poboljšana njihova katalitička sposobnost., Ever rising needs for renewable energy, in order to decrease pollution and exploitation of limited fossil resources, have caused intensive research on the use of eco friendly fuels. Hydrogen electrooxidation in fuel cells is a promissing process of zero-emission energy production from a renewable source. Furthermore, using small organic molecules (SOMs) such as formic acid, instead of hydrogen, makes this process safer and fuel transportation easier to manage. Oxidation of SOMs in fuel cells requires a noble metal as catalyst, capable of enabling dehydrogenation of SOM as an initial step of the reaction. Bimetallic PtAu catalysts are the best catalysts for formic acid oxidation so far, due to the ensemble effect of Au on Pt which favors the direct oxidation of formic acid, avoiding the formation of CO that acts as a catalytic poison. In this reseach carbon supported PtAu nanocatalysts were synthesized by a microemulsion method, in presence of a capping agent that affected the particle shape, which made further improvement in catalytic performance of these nanoparticles.

Formic acid is one of the most promising small organic molecules that can be used as fuel in polymer electrolyte fuel cells. These systems are recognized as high-efficiency energy conversion devices which could offer energy generated from electrochemical processes. At carbon supported platinum nanoparticles as state of the art anodic catalysts formic acid oxidation reaction (FAOR) proceeds through a dual path mechanism that includes the formation of CO in the indirect reaction pathway. Since CO is a catalytic poison, the best way to address this problem is to synthesize catalysts that would either provide prompt CO oxidation and removal, or favour the direct reaction pathway to completely avoid CO formation and electrode poisoning. PtAu systems are considered as efficient catalysts for FAOR due to the ensemble effect of Au on Pt, however the optimal ratio of these two elements is still quite vague. Given the experience with water in oil microemulsion synthesis for preparation of shape controlled Pt nanoparticles,1 bimetallic PtAu/C nanocatalysts were synthesized by the same procedure, following a simultaneous precursor reduction methodology.2 The amount of the capping agent used, was varied in order to cause formation of nanoparticles with different shape (cubic or tetrahedron like). Addition of a very low, but very finely dispersed amount of Au significantly increases the catalytic activity, and also affects kinetic of the particle growth, influencing the particle shape. Ordered structure of these particles contributes to their stability as well. These results were obtained by Electrochemical and High Resolution Transmission Electron Microscopy characterization (HRTEM) with Energy Dispersive X-ray Spectroscopy (EDXS), along with X-Ray Diffraction and (XRD) and X-Ray Photoelectron Spectroscopy (XPS).

PtAu systems are recognized as good catalysts for the oxidation of formic acid electrooxidation, which is investigated as a possible anodic reaction in low-temperature fuel cells. In this research, bimetallic PtAu nanoparticles, supported on high area carbon Vulcan XC-72R, were synthesized by water in oil microemulsion method. The precursor reduction process took place in a single microemulsion, simultaneously, in the presence of 35% of HCl in the water phase, as a capping agent. Electrochemical behavior of the PtAu/C catalyst was investigated at as prepared electrodes by cyclic voltammetry in 0.5M H2SO4 as a supporting electrolyte, and also in the oxidation of adsorbed CO. The results were compared to the Pt/C catalyst prepared by the same synthesis procedure. PtAu/C catalyst powder was also characterized by X-Ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Average particle diameter, of 2nm, was calculated from XRD data, which is close to the value of 2.82 nm obtained from TEM images. Compared to identically synthesized Pt nanoparticles, the bimetallic ones are significantly smaller. EDS maps of PtAu/C sample confirm the presence of both elements, and indicate a very fine distribution of Au in the sample. Elemental composition of about 20% Au and 80% Pt was also determined from these maps. Prepared catalyst was tested for formic acid electro-oxidation in terms of its activity and stability over the long term cycling. The voltammograms recorded indicate the change of reaction mechanism and better utilization of the catalyst surface in comparison to Pt/C., PtAu sistemi se smatraju veoma dobrim katalizatorima za elektrooksidaciju mravlje kiseline, kao moguće anodne reakcije u niskotemperaturnim gorivnim galvanskim spregovima. U ovom radu bimetalne PtAu nanočestice sintetizovane su mikromulzionim postupkom, i u toku sinteze nanete na ugljenični nosač Vulcan XC-72R. Procesi redukcije prekursora odigravaju se simultano, unutar vodene faze iste mikroemulzije, u prisustvu 35% HCl. Elektrohemijske karakteristike katalizatora ispitivane su cikličnom voltametrijomv na 'as prepared' elektrodama u 0.5M H2SO4 kao osnovnom elektrolitu, kao i prilikom oksidacije adsorbovanog CO. Rezultati su upoređeni sa Pt/C katalizatorom sintetizovanim istim postupkom i pod istovetnim uslovima. Pripremljeni PtAu/C prah okarakterisan je takođe difrakcijom X-zraka, transmisionom elektronskom mikroskopijom i energetski disperzionom spektroskoijom. Veličina čestice određena analizom difraktograma X-zraka iznosi 2nm, što je blisko vrednosti dobijenoj analizom TEM snimaka od 2.82 nm. U poređenju sa Pt nanočesticama sintetizovanim na isti način, bimetalne nanočestice su znatno manjeg prečnika. Mape uzorka PtAu/C dobijene energetski disperzionom spektroskopijom potvrđuju prisustvo oba elementa i pokazuju veoma finu distribuciju Au u uzorku. Analizo mapa utvrđeno je i da je katalizator sastava 20% Au i 80% Pt. Konačno, ispitane su aktivnost i stabilnost bimetalnog katalizatora za oksidaciju mravlje kiseline. Snimljeni voltamogrami ukazuju na promenu reakcionog mehanizma i bolje iskorišćenje površine katalizatora u poređenju ra Pt/C katalizatorom sintetizovanim istim postupkom.

The AgPd alloys were electrodeposited onto Au and glassy carbon disc electrodes from the solution containing 0 001 mol dm(-3) PdCl2 + 0.04 mol dm(-3) AgCl + 0.1 mol dm(-3) HCl + 12 mol dm(-3) LiCl under the non-stationary diffusion (quiescent electrolyte) and convective diffusion (omega = 1000 rpm) to the different amounts of charge and at different current densities. Electro-deposited alloy layers were characterized by the anodic linear sweep voltam-metry (ALSV), scanning electron microscopy, energy dispersive X-ray spectro-scopy (EDS) and X-ray photoelectron spectroscopy (XPS). The compositions of the AgPd alloys determined by the EDS were almost identical to the theoretically predicted ones, while the compositions obtained by XPS and ALSV analysis were similar to each other, but different from those obtained by EDS. Deviation from the theoretically predicted values (determined by the ratio j(L)(Pd)/j(Ag)) was more pronounced at lower current densities and lower charges of AgPd alloys electrodeposition, due to the lower current efficiencies for alloys electrodeposition. The ALSV analysis indicated the presence of Ag and Pd, expressed by two ALSV peaks, and in some cases the presence of the additional peak, which was found to correspond to the dissolution of large AgPd crystals, formed at thicker electrodeposits (higher electrodeposition charge), indicating, for the first time, that besides the phase structure, the morphology of alloy electrodeposit could also influence the shape of the ALSV response. In addition to Ag and Pd, the XPS analysis confirmed the presence of AgCl at the surface of samples electrodeposited to low thicknesses (amounts of charge).

PtAu systems are recognized as good catalysts for the oxidation of formic acid electrooxidation, which is investigated as a possible anodic reaction in low-temperature fuel cells. In this research, bimetallic PtAu nanoparticles, supported on high area carbon Vulcan XC-72R, were synthesized by water in oil microemulsion method. The precursor reduction process took place in a single microemulsion, simultaneously, in the presence of 35% of HCl in the water phase, as a capping agent. Electrochemical behavior of the PtAu/C catalyst was investigated at as prepared electrodes by cyclic voltammetry in 0.5M H2SO4 as a supporting electrolyte, and also in the oxidation of adsorbed CO. The results were compared to the Pt/C catalyst prepared by the same synthesis procedure. PtAu/C catalyst powder was also characterized by X-Ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Average particle diameter, of 2nm, was calculated from XRD data, which is close to the value of 2.82 nm obtained from TEM images. Compared to identically synthesized Pt nanoparticles, the bimetallic ones are significantly smaller. EDS maps of PtAu/C sample confirm the presence of both elements, and indicate a very fine distribution of Au in the sample. Elemental composition of about 20% Au and 80% Pt was also determined from these maps. Prepared catalyst was tested for formic acid electro-oxidation in terms of its activity and stability over the long term cycling. The voltammograms recorded indicate the change of reaction mechanism and better utilization of the catalyst surface in comparison to Pt/C., PtAu sistemi se smatraju veoma dobrim katalizatorima za elektrooksidaciju mravlje kiseline, kao moguće anodne reakcije u niskotemperaturnim gorivnim galvanskim spregovima. U ovom radu bimetalne PtAu nanočestice sintetizovane su mikromulzionim postupkom, i u toku sinteze nanete na ugljenični nosač Vulcan XC-72R. Procesi redukcije prekursora odigravaju se simultano, unutar vodene faze iste mikroemulzije, u prisustvu 35% HCl. Elektrohemijske karakteristike katalizatora ispitivane su cikličnom voltametrijomv na 'as prepared' elektrodama u 0.5M H2SO4 kao osnovnom elektrolitu, kao i prilikom oksidacije adsorbovanog CO. Rezultati su upoređeni sa Pt/C katalizatorom sintetizovanim istim postupkom i pod istovetnim uslovima. Pripremljeni PtAu/C prah okarakterisan je takođe difrakcijom X-zraka, transmisionom elektronskom mikroskopijom i energetski disperzionom spektroskoijom. Veličina čestice određena analizom difraktograma X-zraka iznosi 2nm, što je blisko vrednosti dobijenoj analizom TEM snimaka od 2.82 nm. U poređenju sa Pt nanočesticama sintetizovanim na isti način, bimetalne nanočestice su znatno manjeg prečnika. Mape uzorka PtAu/C dobijene energetski disperzionom spektroskopijom potvrđuju prisustvo oba elementa i pokazuju veoma finu distribuciju Au u uzorku. Analizo mapa utvrđeno je i da je katalizator sastava 20% Au i 80% Pt. Konačno, ispitane su aktivnost i stabilnost bimetalnog katalizatora za oksidaciju mravlje kiseline. Snimljeni voltamogrami ukazuju na promenu reakcionog mehanizma i bolje iskorišćenje površine katalizatora u poređenju ra Pt/C katalizatorom sintetizovanim istim postupkom.

In this research, a water-in-oil microemulsion method with HCl as a capping agent was applied to synthesize carbon supported Pt catalysts. Varying the concentration of HCl caused changes in the shape of obtained nanoparticles, i.e. preferential growth of certain facets. Addition of catalyst support in the synthesis process facilitated the cleaning procedures necessary to remove the surfactant residues. Prepared catalyst powders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis indicated the influence of HCl addition on the crystallite size and crystal habit. TEM revealed that addition of higher amounts of the capping agent led to the formation of a noticable amount of particles with concave cubic or branched-like structures. Influence of the catalyst particles shape on its electrochemical properties was tested in the oxidations of COads, ammonia and formic acid. The latter one was examined in terms of both activity and stability of as prepared and oxide-annealed (electrochemically treated) catalysts. The results clearly demonstrate that even small changes in the nanoparticle surface structure give rise to distinct modifications in their properties. Concave cubic particles, in comparison to other catalysts, show improved catalytic properties and the contribution of their preferentially oriented {100} facets is electrochemically detectable.

Pt nanoparticles supported on Vulcan XC-72R were synthesized by water-in-oil microemulsion method. By incorporating different amounts of HCl as a capping agent in the precursor-containing water phase, nanoparticle shape was varied. Influencing the growth of certain facets leads to the changes of the particle shape depending on the preferential facets. As a result, nanoparticles exhibit some of the electrochemical features typical for single crystals. Commonly employed synthesis procedure for water-in-oil microemulsion method was altered with the addition of catalyst support in the system and changing the catalyst cleaning steps. Prepared catalysts were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and electrochemical methods. Activity and stability for methanol oxidation reaction (MOR), a structure-sensitive reaction, were tested. Electrochemical results reveal the influence of particle size, shape and exposed facets on the electrochemical processes. TEM investigations confirm electrochemical findings, while TGA verifies Pt loading in catalyst powder. Based on the results, optimal HCl concentration for cubic particle formation is determined, and structural effect on MOR activity and stability was tested. Cuboidal NPs show very good reaction activity and fair stability under applied experimental conditions.

Pt nanoparticles supported on Vulcan XC-72R were synthesized by water-in-oil microemulsion method. By incorporating different amounts of HCl as a capping agent in the precursor-containing water phase, nanoparticle shape was varied. Influencing the growth of certain facets leads to the changes of the particle shape depending on the preferential facets. As a result, nanoparticles exhibit some of the electrochemical features typical for single crystals. Commonly employed synthesis procedure for water-in-oil microemulsion method was altered with the addition of catalyst support in the system and changing the catalyst cleaning steps. Prepared catalysts were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and electrochemical methods. Activity and stability for methanol oxidation reaction (MOR), a structure-sensitive reaction, were tested. Electrochemical results reveal the influence of particle size, shape and exposed facets on the electrochemical processes. TEM investigations confirm electrochemical findings, while TGA verifies Pt loading in catalyst powder. Based on the results, optimal HCl concentration for cubic particle formation is determined, and structural effect on MOR activity and stability was tested. Cuboidal NPs show very good reaction activity and fair stability under applied experimental conditions.

Two types of iridium oxide films formed at the Ti-2 AlC substrate were investigated: (1) anodically electrodeposited iridium oxide film from the solution based on IrCl(3)xH(2)O; (2) iridium oxide film prepared by cycling thin layer of electrodeposited Ir in the 0.5 M H2SO4 from - 0.25 to 1.20 V. It was shown that during anodic electrodeposition of iridium oxide film (1) coulombic efficiency decreases with increasing anodic potential, being only 3% atE = 0.7 V vs. SCE and 26% atE = 0.62 V vs. SCE. A pair of peaks corresponding to the transition Ir(III)-oxide/Ir(IV)-oxide was present on the CVs recorded in 0.5 M H2SO4. While cycling pure Ir thin layer in the solution of 0.5 M H2SO4 from - 0.25 to 1.20 V (2) up to 100 cycles, typical CV response was characterized with the prepeak and a pair of peaks corresponding to the Ir(III)/Ir(IV)-oxide transition. With the increase of cycles number to 150, additional peak at potential of 1.0 V appeared. This peak was formed on the account of pair of peaks corresponding to the Ir(III)/Ir(IV)-oxide transition. The oxygen evolution reaction (OER) was investigated at both iridium oxide films. It was shown that the Tafel slope for the OER was similar to 40 mV dec(-1)for the first polarization curve, confirming that the rds was a reaction S-OH - gt S-O-ads + H++ e(-). As the number of recorded polarization curves increased, the activity of both types of iridium oxide films decreased, due to dissolution of iridium oxide films at the potentials of the OER. It is shown that anodically electrodeposited iridium oxide film is more active for the OER than that obtained by cycling electrodeposited iridium layer. However, both iridium oxide films exhibited insufficient stability.