Browsing by Author "Sljukic, Biljana"

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Mn2o3-Mo (Mo = Zro2, V2o5, Wo3) Supported Ptni Nanoparticles: Designing Stable and Efficient Electrocatalysts for Oxygen Reduction and Borohydride Oxidation
(Elsevier Science Bv, 2019) Martins, Marta; Milikic, Jadranka; Sljukic, Biljana; Soylu, Gulin S. P.; Yurtcan, Ayse B.; Bozkurt, Gamze; Santos, Diogo M. F.
PtNi nanoparticles (NPs) are synthesised by microwave irradiation technique and anchored onto three binary metal oxide (BMO) supports, namely Mn2O3-ZrO2, Mn2O3-V2O5 and Mn2O3-WO3, prepared by solid-state dispersion method. The BMO supports are characterised using SEM, FTIR, N-2-sorption and electrical conductivity measurements. XRD, XPS and TEM analysis confirm the formation of PtNi NPs on the BMO supports. Pt and Ni content over the support materials is set to 10 wt.% for each element. These electrocatalysts activity for oxygen reduction (ORR) and borohydride oxidation (BOR) reaction in alkaline media is assessed for the first time using voltammetric and chronoamperometric techniques. All three PtNi electrocatalysts revealed activity for ORR and BOR, with PtNi/(Mn2O3- ZrO2) exhibiting the highest current densities. The ORR onset potentials were observed to range from 0.84 to 0.97 V vs. RHE, with Tafel slopes ranging from 0.101 to 0.230 V dec(-1). BOR activation energies were found to range from 27 to 30 kJ mol(-1). Obtained results point out PtNi/(Mn2O3- ZrO2) as suitable electrocatalyst for fuel cell applications, particularly for BOR, with lower catalyst price due to partial replacement of the noble metal by a transition metal and improved stability achieved by introducing a binary metal oxide support.
Pt-Decorated Binary Transition Metal Oxides (MnO-NiO, MnO-TiO2) for Enhanced Electrocatalysis of Oxygen Reduction and Borohydride Oxidation
(Elsevier, 2024) Martins, Marta; Bozkurt, Gamze; Bayrakceken, Ayse; Soylu, Gulin S. Pozan; Sljukic, Biljana; Santos, Diogo M. F.
Integrating transition metal oxides with precious metals is a strategic approach to designing cost-effective electrocatalysts with enhanced stability. Herein, platinum (Pt) nanoparticles (NPs) were prepared by microwave irradiation and anchored onto MnO and two binary metal oxides, MnO-NiO and MnO-TiO2, obtained by solid-state dispersion. Voltammetric and electrochemical impedance spectroscopy techniques evaluated their performance for oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) in alkaline media. Tafel slope and the number of exchanged electrons, n, were determined to compare the three electrocatalysts' performance for fuel cell applications. Pt/MnO-NiO revealed a Tafel slope of 177 mV dec(-1) for ORR and an n value of ca. 4 and 3 e(-) for ORR and BOR, respectively. These findings demonstrate that Pt NPs supported on binary metal oxide supports, particularly Pt/MnO-NiO, are promising electrocatalysts for ORR and BOR in alkaline media, thus recommending their use in direct borohydride fuel cells.
Tailoring Metal-Oxide PtNi as Bifunctional Catalysts of Superior Activity and Stability for Unitised Regenerative Fuel Cell Applications
(Elsevier Science Inc, 2021) Mladenovic, Dusan; Santos, Diogo M. F.; Bozkurt, Gamze; Soylu, Gulin S. P.; Yurtcan, Ayse B.; Miljanic, Scepan; Sljukic, Biljana
Three different metal oxides based on Mn2O3 with TiO2 or NiO were synthesised. Pt or PtNi nanoparticles were anchored on each support, creating a set of nine samples that were tested for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). PtNi/Mn2O3-NiO showed the most promising results for ORR as evidenced by the lowest Tafel slope, the highest diffusion-limited current density and number of electrons exchanged, along with the highest stability. The best performance of PtNi/Mn2O3-NiO reflects its highest electrochemical surface area and the lowest charge-transfer resistance. Furthermore, this catalyst showed high activity for the OER as evidenced by the low Tafel slope and high current density at an overpotential of 400 mV. The present study indicated different active sites for the two reactions, i.e., PtNi NPs for the ORR and NiO for the OER.