Browsing by Author "Gozeten, Ibrahim"

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The Catalytic Activity of Halloysite-Supported Ru Nanoparticles in the Methanolysis of Sodium Borohydride for Hydrogen Production
(Pergamon-elsevier Science Ltd, 2023) Gozeten, Ibrahim; Karakas, Kadir; Karatas, Yasar; Tunc, Mehmet; Gulcan, Mehmet
Finding environmentally friendly new energy sources is very urgent for a sustainable and clean energy future. It is vital to reach clean energy sources such as hydrogen, which does not create a polluting by-product when burned with oxygen. In this study, for a livable clean universe, hydrogen production studies were carried out from sodium borohydride (NaBH4), which is a very good hydrogen storage material, in a methanolysis environment, over ruthenium nanoparticles (Ru (0) NPs) impregnated on halloysite (Hall) support ma-terial (Ru (0)@Hall) at room conditions. The catalytic performance of the newly synthesized Ru (0)@Hall nanocatalyst was tested in the NaBH4 methanolysis reaction for hydrogen production. It was determined that Ru (0)/Hall nanocatalyst showed excellent activity (initial turn-over frequency (TOFinitial) = 1882 h-1; 31.37 min-1) and reusability (at the end of the 5th cycle, it retained 90% of its initial activity) performance in the catalytic meth-anolysis of NaBH4. The analyzes of the Ru (0)@Hall nanocatalyst, both fresh and at the end of the 5th catalytic cycle, were made with advanced analytical methods (ICP-OES, XRD, XPS, SEM, HRTEM, TEM, TEM-EDX, BET) and the nature of the catalytic material was clarified. The results showed the homogeneous distribution of Ru (0) NPs on the Hall surface (mean size = 1.53 +/- 0.17 nm). Kinetic studies of hydrogen production from catalytic methanolysis reaction of NaBH4 were performed based on nanocatalyst [Ru (0)@Hall], substrate [NaBH4] concentrations, and temperature (298-318 K). From the kinetic data, the kinetic parameters (Ea, DH*, and DS*) were calculated and the rate equation was determined.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Palladium Nanoparticles Supported on Activated Carbon (C) for the Catalytic Hexavalent Chromium Reduction
(Springer int Publ Ag, 2022) Gozeten, Ibrahim; Tunc, Mehmet
Hexavalent chromium is widely used in industry and causes human health and environmental problems due to its extremely toxic properties. On the contrary, trivalent chromium is necessary for living ecosystems. Therefore, reducing hexavalent chromium to trivalent chromium is the best strategy for detoxifying hexavalent chromium. Pd(0)@C nanocatalyst was prepared by a simple impregnationreduction method in solution under mild conditions at 298 K and was identified by XPS, XRD, TEM, TEM-EDX, HR-TEM, and ICP-OES analyses. TEM results showed that very well-dispersed Pd nanoparticles were formed on the C surface (mean particle sizes 3.98 +/- 0.24 nm). The catalytic performance of Pd(0)NPs impregnated on cheap and easily available commercial activated carbon were tested as heterogeneous nanocatalysts in the catalytic reduction of hexavalent chromium in the medium of formic acid, which is a good reducing agent, and sodium formate as the promoter at 298 K. It was determined that the formed Pd(0) nanoclusters could successfully reduce Cr(VI) to Cr(III) with high selectivity (similar to 97%) in formic acid and sodium formate solution under mild conditions. It was also observed that the Pd(0)@C catalyst retained a significant (>75%) initial activity even after the 5th use. In addition, the kinetic studies of the catalytic reduction reaction of Cr(VI) catalyzed by Pd(0)@C nanoparticles were investigated depending on the substrate [Cr2O72-], catalyst [Pd(0)@C], sodium formate [HCOONa], formic acid [HCOOH] concentrations, and temperature parameter. From the rich kinetic data obtained, the nature of the velocity equation was explained, and the activation parameters were calculated.
Palladium Nanoparticles Supported on Aluminum Oxide (Al2o3) for the Catalytic Hexavalent Chromium Reduction
(Springer, 2022) Gozeten, Ibrahim; Tunc, Mehmet
While Cr(VI), a hazardous industrial waste, is an acute toxic, carcinogenic, and proven mutagenic pollutant, Cr(III) is thought to be an essential element for living things. In this study, Pd(0)@ Al2O3 nanoclusters supported on Al2O3 were reproducibly prepared in aqueous solution at 25 degrees C by a simple impregnation-reduction method. The results showed that Pd(0)@Al2O3 nanoclusters with average particle size of 3.01 +/- 0.19 nm were formed, well dispersed over the Al2O3 surface. The Al2O3-supported Pd(0)@Al2O3 nanoclusters were used as heterogeneous nanocatalysts in the catalytic reduction of Cr(VI) in formic acid medium, which is a good reducing agent under mild conditions. It has been observed that catalyst Pd(0)@Al2O3 can catalyze the catalytic reduction of Cr(VI) with high selectivity (- %99) and efficiency (TOF) (138 mol Cr2O72-/ mol Pd min.). More importantly, the exceptional stability of the Pd(0)@Al2O3 nanocatalyst against flocculation, leaching, and CO poisoning showed that this catalyst is a reusable catalytic material in the catalytic reduction reaction of Cr(VI). It was observed that the Pd(0)@Al2O3 catalyst maintained a significant (> 84%) initial TOF value even after the 5th use. The Pd(0)@Al2O3 nanocatalyst was identified by advanced analytical methods (XPS, XRD, TEM, TEM-EDX, HR-TEM, ICP-OES). In addition, for the kinetic data of the catalytic reduction reaction of Cr(VI) catalyzed by Pd(0)@Al2O3, the rate equation and Ea, Delta H-#, and Delta S-# activation parameters were derived depending on the [catalyst], [Cr2O72-], [HCOOH], and [HCOONa] concentrations and temperature.
Volcanic Ash-Supported Ruthenium Nanoparticles as Effective Catalysts for Hydrogen Production From Ammonia Borane Methanolysis
(Elsevier, 2025) Gozeten, Ibrahim
In the increasing search for renewable clean energy, boron-based hydrogen carrier materials offer excellent advantages. Ammonia borane (H3NBH3, AB) is a solid hydrogen-rich molecular crystal material derived from boron mineral. Recently, it has become a remarkable material in the field of hydrogen production due to its high hydrogen content and controlled hydrogen release properties. Herein, the first synthesis, characterization, and catalytic performance of volcanic ash (VA)-grafted ruthenium nanoparticles (Ru(0)NPs) for H2 evolution from methanolysis of AB are reported. Ru(0)NPs supported on VA (Ru(0)NPs@VA) were synthesized and used as a high-performance catalyst in the methanolysis dehydrogenation of AB at room temperature. VA-decorated Ru(0) NPs solid catalytic materials were stable during isolation processing and characterized by FTIR, N2 adsorptiondesorption, ICP-OES, SEM-elemental mapping, SEM, SEM-EDX, XPS, HRTEM, TEM-EDX, TEM, XRD techniques. The results of the analysis the formation of excellent-distributed Ru(0)NPs by an average nanocrystal size of 1.37 +/- 0.52 nm on the VA support surface area, which keeps the host matrices stable. The Ru(0)NPs@VA nanocatalyst rapidly released 3.0 equivalents of hydrogen per mole of AB at 298 K, demonstrating a highly effective nanocatalyst property in the methanolysis dehydrogenation of AB by an TOFinitial value of 50.14 min(-1). VA-grafted Ru (0) NPs can be isolated, bottled, redispersed and reused as a very active nanocatalyst in the methanolysis of AB even at low doses and temperatures. In this study, all experimental details of a new set of kinetic data to determine the rate law of catalytic methanolysis AB are revealed, and the activation parameters (Ea, Delta H/= and Delta S/=) of the rate equation are calculated based on these data.