Nanoyapılı Multimetalik Pt-Sn-Cs/C ve Pt-M/C (M=Ag, Ca, Cd, Cs, Cu, Fe, Ir, Mg, Pd, Sn, Zr) Doğrudan Beslemeli Etanol Yakıt Pili Katalizörlerinin Elektrokatalitik Özellikleri

Carbon supported Pt and Pt-M (M=Ag, Ca, Cd, Cs, Cu, Fe, Ir, Mg, Pd, Sn, Zr) bimetallic nanocatalysts (10% Pt loading) and Pt-Sn-Cs trimetallic nanocatalysts were prepared by ethylene glycol (EG) reduction method. The ethanol electrooxidation (EOR) performance of these catalysts were studied by cyclic voltammetry (CV), chronoamperometry (CA), electrochemical impedance spectroscopy (EIS) techniques. Considering Pt-M bimetallic nanocatalysts, carbon supported Pt-Sn bimetallic nanocatalyst showed the best EOR activity as a result of these CV, CA, EIS measurements. Furthermore, Cs promoted Pt bimetallic nanocatalyst also improved the activity of reverse current, attributed to the basic character of Cs. Pt-Sn nanocatalyst was promoted by Cs to neutralize the surface acid sites of the Pt-Sn nanocatalyst. Pt-Sn-Cs/C nanocatalyst showed the superior activity compared to Pt-Sn nanocatalysts. Hence, we further performed EIS measurements on Pt-Sn-Cs, Pt-Sn, Pt-Cs nanocatalysts to compare their electrocatalytic activities.Karbon destekli Pt ve Pt-M (M=Ag, Ca, Cd, Cs, Cu, Fe, Ir, Mg, Pd, Sn, Zr) bimetalik nanokatalizörler (10% Pt yüklemesi) ve Pt-Sn-Cs trimetalik nanokatalizörler etilen glikol (EG) indirgenme yöntemi ile hazırlanır. Etanol elektro oksitlenme (EOR) performansları döngüsel voltametre (CV), kronoamperometre (CA) ve elektrokimyasal impedans spektroskopisi (EIS) yöntemleri ile çalışılmıştır. Yapılan CV, CA ve EIS ölçümleri sonucunda bimetalik nanokatalizörlerinden karbon destekli Pt-Sn kalay katalizörü en iyi EOR aktivitesini göstermiştir. Ayrıca, Cs katkılanmış Pt bimetalik katalizöründe geri akım pikin aktivitesinin arttığı gözlenmiştir. Bu artışın sebebi Cs metalinin bazik karakterde olmasına bağlanmıştır. Pt-Sn bimetalik nanokatalizörü de Pt-Sn katalizörünün yüzeyindeki asit sitelerini nötralize etmek amacı ile Cs ile katkılanmıştır. Pt-Sn-Cs/C trimetalik katalizörü Pt-Sn da dahil olmak üzere diğer bimetalik katalizörler ile karşılaştırıldığında en iyi aktiviteyi göstermiştir. Bu yüzden Pt-Sn-Cs, Pt-Sn, Pt-Cs nanokatalizörleri üzerinde EIS ölçümleri yapılarak bu katalizörlerin elektrokimyasal özellikleri ayrıntılı olarak incelenmiştir

Etanol elektro-oksitlenme katalizörlerinin sentezlenmesi ve karakterizasyonu.

In this study, the role of defects, the role of Sn in relation to defects, and the role of oxide phase of tin in ethanol electro-oxidation reaction were investigated. Firstly, adsorption calorimetry measurements were conducted on monometallic (1%Pt, 2%Pt, and 5%Pt) and bi-metallic (5% Pt-Sn) γ-Al2O3 supported Pt catalysts. It was observed that while saturation coverage values decreased, intermediate heats remained same for Pt-Sn catalysts by the increasing amount of tin. The effect of particle size was investigated on Pt/C (pH=5), Pt/C (pH=11) catalysts at different scan rates. At high scan rates (quite above diffusion limitations), current per site activities were nearly the same for 20% Pt/C (E-Tek), Pt/C (pH=11), and Pt/C (pH=5) catalysts, which explained as electro-oxidation reaction takes place at the defects sites. Furthermore, the effect of support on ethanol electro-oxidation was investigated on CNT supported Pt catalyst. Results indicate that only the metal dispersions improved ethanol electro-oxidation reaction and support did not have any effect on ethanol electro-oxidation reaction. Results on the 20% Pt-Sn/C (15:1 to 1:1 Pt: Sn atomic ratios) and 20% Pt-SnO2/C (6:1 and 1:1) catalysts indicated that ethanol electro-oxidation activity increased by increasing tin amount. For 20% Pt-Sn/C catalysts, Pt-Sn (6:1)/C indicated best activity. On the other hand, 20% Pt-SnO2 (6:1)/C catalyst was better than Pt-Sn (6:1)/C in terms of ethanol electro-oxidation activity due to the fact that there was low contact between Pt and tin oxide particles.Ph.D. - Doctoral Progra

A novel experimental and density functional theory study on palladium and nitrogen doped few layer graphene surface towards glucose adsorption and electrooxidation

At present, few layer graphene (G) and nitrogen doped few layer graphene (N doped-G) are firstly coated on Cu foil via chemical vapor deposition (CVD) method and G and N doped-G coated Cu foil is transferred to the indium tin oxide (ITO) substrate surface to obtain electrodes. Pd metal is electrodeposited onto the N doped-G/ITO electrode (Pd-N doped-G/ITO). Pd-N doped-G/ITO electrode are characterized with advanced surface characterization methods such as Raman spectroscopy and SEM-EDX. Characterization results reveal that G and N structures are succesfully obtained and the presence of Pd on Pd-N doped-G/ITO is confirmed with SEM-EDX mapping. The cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) are employed to examine glucose electrooxidation of G/ITO, N-doped G/ITO, and Pd-N-doped G/ITO electrodes. P-N-dopedG/ITO electrode exhibits the best glucose electrooxidation activity with 2 mA/cm(2) specific activity. Density functional theory (DFT) calculations are also carried out to better understand the interaction of the molecules on Pd modified G (Pd-G) and Pd modified N-doped G (Pd-3NG) surfaces

A comparative experimental and density functional study of glucose adsorption and electrooxidation on the Au-graphene and Pt-graphene electrodes

At present, the graphene is covered on Cu foil with the 5 sccm hexane (C6H14) flow rate, 50 sccm hydrogen (H-2) flow rate, and 20 min deposition time parameters by the CVD method. The graphene on the Cu foil is then covered onto few-layer ITO electrode. Furthermore, the Pt and Au metals are electrodeposited on graphene/ITO electrode with electrochemical method. These electrodes are characterized by Raman spectroscopy and Scanning Electron Microscopy-Energy Dispersive X-Ray analysis (SEM-EDX). The graphene structure is approved via Raman analysis. Au, Pt, and graphene network are openly visible from SEM results. In addition, glucose (C6H12O6) electrooxidation is investigated with cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. As a result, Pt-graphene/ITO indicates the best C6H12O6 electrooxidation activity with 9.21 mA cm(-2) specific activity (highly above the values reported in the literature). In all electrochemical measurements, Pt-graphene/ITO exhibits best electrocatalytic activity, stability, and resistance compared to the other electrodes. The adsorption of the C6H12O6 molecule is examined theoretically over metal atom (gold and platinum)-doped graphene surfaces using the density functional theory (DFT) method. The interaction between C6H12O6 molecule and OH adsorbed Pt-doped surface is stronger than that of OH adsorbed Au-doped graphene surface thermodynamically according to the reaction energy values. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

A Critical Overview of the State-of-the-Art Methods for Biogas Purification and Utilization Processes

Biogas is one of the most attractive renewable resources due to its ability to convert waste into energy. Biogas is produced during an anaerobic digestion process from different organic waste resources with a combination of mainly CH₄ (~50 mol/mol), CO₂ (~15 mol/mol), and some trace gasses. The percentage of these trace gases is related to operating conditions and feedstocks. Due to the impurities of the trace gases, raw biogas has to be cleaned before use for many applications. Therefore, the cleaning, upgrading, and utilization of biogas has become an important topic that has been widely studied in recent years. In this review, raw biogas components are investigated in relation to feedstock resources. Then, using recent developments, it describes the cleaning methods that have been used to eliminate unwanted components in biogas. Additionally, the upgrading processes are systematically reviewed according to their technology, recovery range, and state of the art methods in this area, regarding obtaining biomethane from biogas. Furthermore, these upgrading methods have been comprehensively reviewed and compared with each other in terms of electricity consumption and methane losses. This comparison revealed that amine scrubbing is one the most promising methods in terms of methane losses and the energy demand of the system. In the section on biogas utilization, raw biogas and biomethane have been assessed with recently available data from the literature according to their usage areas and methods. It seems that biogas can be used as a biofuel to produce energy via CHP and fuel cells with high efficiency. Moreover, it is able to be utilized in an internal combustion engine which reduces exhaust emissions by using biofuels. Lastly, chemical production such as biomethanol, bioethanol, and higher alcohols are in the development stage for utilization of biogas and are discussed in depth. This review reveals that most biogas utilization approaches are in their early stages. The gaps that require further investigations in the field have been identified and highlighted for future research.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacultyResearche

Comparative investigation of multi-walled carbon nanotube modified diesel fuel and biogas in dual fuel mode on combustion, performance, and emission characteristics

© 2021Biogas has been investigated as an alternative biofuel in dual fuel operating mode in a direct injection diesel engine. However, there is not sufficient information about using modified fuels with biogas. This study aimed to investigate the effects of modified diesel fuel and biogas on combustion behavior, performance, and emissions characteristics at 1500 rpm constant speed with 5 different load conditions at an interval of 25%. Diesel was modified with multi-walled carbon nanotubes with 30, 60, and 90 ppm. Diesel fuel and three modified fuels were used as pilot fuel and biogas was introduced through the intake manifold with the flow rate of 500 g/h as the primary fuel. Diesel mode fuels were denominated F1 while dual fuel mode fuels were labeled as F2, and the concentration levels were given subscript such as F2 @60ppm. The experimental study revealed that modified fuel showed better combustion behaviors, performance, and emissions in comparison to diesel fuel. Further, the same trend was observed in the dual fuel mode. The maximum pressure of F2 @60 ppm was 1% higher than F2 under dual fuel mode at the full load. Moreover, the coefficient of variation of the indicated mean effective pressure for dual fuel mode was found approximately 9.2, 6.9, 6.2, and 7.2% for F2, F2 @30 ppm, F2 @60 ppm, and F2 @90 ppm, respectively at full load. In addition, the energy share of biogas increased by 7.9, 8.7, and 7.1% for F2 @30 ppm, F2 @60 ppm, and F2 @90 ppm, respectively in comparison with F2 at full load. The highest decrease of brake specific energy consumption under the dual mode was obtained to be an 8% drop from F2 @60 ppm compared to F2 at full load. At the same load, the brake thermal efficiency of F2 @30 ppm, F2 @60 ppm, and F2 @90 ppm were noted to be 30.2, 30.4, and 30.0%, respectively which are higher than F2 (27.9%). The value of replaced diesel with biogas was noted 0.09, 0.23, 0.24, and 0.22 kg/h for F2, F2 @30 ppm, F2 @60 ppm, and F2 @90 ppm, respectively under the full load condition. Lastly, CO and HC emissions were almost the same value with and without modified fuel for dual fuel mode at the full load. Nevertheless, NO emission was slightly increased with modified fuel compared to F2. From these findings, it can be suggested that 60 ppm multi-walled carbon nanotubes additive can be an optimum level for combustion, performance, and emissions under the dual fuel mode