Yunus Yıldız

Bio: Yunus Yıldız is an academic researcher from Dumlupinar University. The author has contributed to research in topics: Catalysis & High-resolution transmission electron microscopy. The author has an hindex of 21, co-authored 22 publications receiving 1362 citations.

Enhanced electrocatalytic activity and durability of Pt nanoparticles decorated on GO-PVP hybride material for methanol oxidation reaction

Abstract: The alternative energy request is force to find effective electro catalysts used in fuel cell implementations and to enhance the efficiency of existing materials. In this study, graphene oxide (GO) and polyvinylpyrrolidone (PVP) supported shape-controlled platinum nanoparticles (Pt NPs) were newly synthesized with one-pot approach and used as anode materials in the direct methanol fuel cells (DMFCs). The examination for the performance of Pt @GO-PVP NPs was carried out in methanol oxidation reactions (MOR). Pt @GO-PVP catalysts exhibit high stability and activity against the MOR. The methanol oxidation reactions current can reach to 43 mA and can maintain 82.9% of the initial value even after 1000 cycles. The GO-PVP support material provides higher surface area and absorbs more methanol molecules for more efficient oxidation.

Enhanced electrocatalytic activity and durability of highly monodisperse Pt@PPy–PANI nanocomposites as a novel catalyst for the electro-oxidation of methanol

Abstract: Highly monodisperse Pt nanocomposites (Pt@PPy–PANI NPs) supported on polypyrrole (PPy)–polyaniline (PANI) have been successfully synthesized for the first time by a simple one-pot process, which involves the simultaneous reduction of the conducting polypyrrole (PPy)–polyaniline (PANI) and Pt precursors using DMAB (dimethylamine borane) as a reductant under ultrasonic conditions. Pt@PPy–PANI NPs have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). All the results show that highly crystalline and stable colloidal Pt@PPy–PANI NPs have been formed as one of the most active and long-lived catalysts with superior reusability performance for the electro-oxidation of methanol at room temperature. Compared to PPy or PANI supported Pt nanoparticles, Pt@PPy–PANI NPs exhibit extraordinary electrocatalytic activity and stability toward the electro-oxidation of methanol, showing their potential use as a new electrode material for direct methanol fuel cells (DMFCs). It should be primarily attributed to the PPy–PANI, which not only provided larger surface area and flaws for the deposition of Pt nanoparticles, but also the adsorption of more methanol molecules for further oxidation.

Dehydrogenation of Ammonia Borane by Metal Nanoparticle Catalysts

Abstract: Ammonia borane (AB), having a high hydrogen density of 19.6 wt %, has attracted much attention as a promising chemical hydrogen storage material. In the past few years, a number of highly active metal nanoparticle (NP) catalysts, which are easy to handle and separate, have been developed for AB dehydrogenation. In this Perspective, we summarize new progress in the development of metal NP catalysts, which are categorized into monometallic and heterometallic catalysts, with excellent activity and high recyclability for different AB dehydrogenation pathways, including solvolysis (hydrolysis and methanolysis) in protic solvents and dehydrocoupling in nonprotic solvents, and we survey the corresponding methods for the regeneration of AB. Moreover, the merits and drawbacks of solvolysis and dehydrocoupling are discussed.

Enantioselective photoredox catalysis enabled by proton-coupled electron transfer

Abstract: The first highly enantioselective catalytic protocol for the reductive coupling of ketones and hydrazones is reported. These reactions proceed through neutral ketyl radical intermediates generated via a concerted proton-coupled electron transfer (PCET) event jointly mediated by a chiral phosphoric acid catalyst and the photoredox catalyst Ir(ppy)2(dtbpy)PF6. Remarkably, these neutral ketyl radicals appear to remain H-bonded to the chiral conjugate base of the Brønsted acid during the course of a subsequent C-C bond-forming step, furnishing syn 1,2-amino alcohol derivatives with excellent levels of diastereo- and enantioselectivity. This work provides the first demonstration of the feasibility and potential benefits of concerted PCET activation in asymmetric catalysis.