Browsing by Author "Patil, B."
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Item Open Access Bioinspired copper coordination polymer catalysts for oxygen reduction reaction(Wiley, 2017) Mishra, R.; Patil, B.; Karadaş, F.; Yılmaz, E.Non–noble metal catalysts have recently emerged as promising alternatives to the expensive platinum catalysts for the oxygen reduction reaction (ORR). In this study, a new domain of materials, copper based coordination polymers, has been investigated as promising catalysts for ORR. The study was inspired by copper incorporating biomolecules, which efficiently catalyse the oxygen reduction reaction in nature. Two coordination polymers, [Cu2(μ−AcO)4Po)]n (shortened as[Cu–A]) and [Cu2(μ−BzO)4Po)]n (shortened as[Cu–B]), incorporating one–dimensional chains of Cu(II) paddle wheel units bridged with phosphineoxide ligands were combined with multi−walled carbon nanotubes (MCNTs) to prepare hybrid electrocatalysts for ORR. The electrochemical analysis demonstrates that [Cu–A] catalyses ORR with 3.24 numbers of electrons with Tafel slopes of 122/83 mV dec−1 while it is 2.37 numbers of electrons with Tafel slopes of 131/84 mV dec−1 for [Cu–B]. Rotating disk electrode measurements and evaluation of Tafel slopes reveal that acetate moieties attached to Cu site shift the onset potential of ORR anodically (ca. 40 mV) compared to the one with benzoate bridging groups. The effect of bridging ligands to the stability and activity of catalysts in alkaline media was also evaluated. This study opens a new perspective for the development of non–platinum ORR catalysts.Item Open Access Catalytic properties of vanadium diselenide: a comprehensive study on ıts electrocatalytic performance in alkaline, neutral, and acidic media(American Chemical Society, 2017) Ghobadi, T. G. U.; Patil, B.; Karadas, F.; Okyay, Ali Kemal; Yilmaz, E.Here, we report the synthesis of vanadium diselenide (VSe2) three-dimensional nanoparticles (NPs) and two-dimensional (2D) nanosheets (NSs) utilizing nanosecond pulsed laser ablation technique followed by liquid-phase exfoliation. Furthermore, a systematic study has been conducted on the effect of NP and NS morphologies of VSe2 in their catalytic activities toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline, neutral, and acidic conditions. Research on VSe2 clearly demonstrates that these morphologies do not have a significant difference for ORR and OER; however, a drastic effect of morphology was observed for HER. The ORR activity of both NSs and NPs involves ∼2.85 numbers of electrons with the Tafel slope of 120 mV/dec in alkaline and neutral pH. In alkaline solution, NPs are proved to be an efficient catalyst for OER with an onset potential 1.5 V; however, for HER, NSs have a better onset potential of −0.25 V. Moreover, the obtained NPs have also better catalytic activity with a 400 mV anodic shift in the onset potential compared to NSs. These results provide a reference point for the future application of VSe2 in energy storage and conversion devices and mass production of other 2D materials.Item Open Access Nanohybrid structured RuO2/Mn2O3/CNF as a catalyst for Na-O2 batteries(Institute of Physics Publishing, 2018) Tovini, M. F.; Patil, B.; Koz, C.; Uyar, Tamer; Yılmaz, E.A 3D RuO2/Mn2O3/carbon nanofiber (CNF) composite has been prepared in this study by a facile two step microwave synthesis, as a bi-functional electrocatalyst towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). RuO2 nanoparticles with the mean size of 1.57 nm are uniformly distributed on Mn2O3 nano-rods grown on electrospun CNFs. The electrocatalytic activity of the composites are investigated towards ORR/OER under alkaline condition. The ternary RuO2/Mn2O3/CNF composite showed superior ORR activity in terms of onset potential (0.95 V versus RHE) and Tafel slope (121 mV dec-1) compared to its RuO2/CNF and Mn2O3/CNF counterparts. In the case of OER, the RuO2/Mn2O3/CNF exhibited 0.34 V over-potential value measured at 10 mA cm-2 and 52 mV dec-1 Tafel slope which are lower than those of the other synthesized samples and as compared to state of the art RuO2 and IrO x type materials. RuO2/Mn2O3/CNF also exhibited higher specific capacity (9352 mAh ) than CNF (1395 mAh ), Mn2O3/CNF (3108 mAh ) and RuO2/CNF (4859 mAh g carbon -1) as the cathode material in Na-O2 battery, which indicates the validity of the results in non-aqueous medium. Taking the benefit of RuO2 and Mn2O3 synergistic effect, the decomposition of inevitable side products at the end of charge occurs at 3.838 V versus Na/Na+ by using RuO2/Mn2O3/CNF, which is 388 mV more cathodic compared with CNF.