Browsing by Author "Demir-Kivrak, H."

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Metal-Free Catalysts for Fuel Cell Applications
(Elsevier, 2022) Ulas, B.; Yagizatli, Y.; Demir-Kivrak, H.
Direct methanol fuel cells (DMFCs) are closer to commercialization than other fuel cells. These energy-conversion systems have extremely high potential, especially for portable devices. But the high cost of these fuel cells is the biggest obstacle to the commercialization of these devices. Many researchers have reported that anode and cathode catalysts account for the highest shares of fuel cell costs. These high costs are mainly driven by the costs of precious metals, which are used as anode and cathode catalysts for fuel cells for their high activity and stability. This chapter examines the preparation, characterization, and performances of platinum-free carbon-based and carbon-based metal-free anode and cathode catalysts for DMFCs. © 2022 Elsevier Inc. All rights reserved.
Metal-Free Catalysts for Hydrogen Production
(Elsevier, 2022) Caglar, A.; Hansu, T.A.; Demir-Kivrak, H.
Catalysts are vital for speeding up the reaction during hydrogen production. Both metal-based and metal-free catalysts are used. Metal-free catalysts are less expensive than metal-based catalysts and do not have the disadvantages of oxidation and poisoning. Metal-free catalysts doped with heteroatoms, carbon materials, and polymers have been investigated for their high catalytic activity in hydrogen production. Carbon materials are typically high-surface-area carbon forms such as activated carbon, carbon nanotubes, fullerene, graphite, and graphene. In addition, heteroatoms are obtained by adding atoms to carbon materials, such as replacing carbon atoms with heteroatoms such as N, P, or B or bonding heteroatoms such as S, CI, Br, or O to the carbon surface. Hydrogen is produced from boron-based chemical hybrids, water, and other sources. Sodium borohydride (NaBH4), ammonium borane (NH3BH3), and hydrazine borane (N2H4BH3) are boron-based hybrid chemical sources. Examining the different production methods of these hydrogen sources is important for achieving cheaper and more efficient hydrogen production. Water splitting is examined in three categories: electrolysis, thermolysis, and photoelectrolysis. Furthermore, catalyst characterization is a technique that must be studied to relate catalytic activities with their properties. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric and differential thermal analysis techniques are examined to determine the composition and structure of metal-free catalyst surfaces. © 2022 Elsevier Inc. All rights reserved.
Oxygen Reduction Reaction; Fuel Cells
(Springer Nature, 2024) Yagizatli, Y.; Acil, G.; Ulas, B.; Demir-Kivrak, H.
The principles of the oxygen reduction reaction (ORR), including elec-trocatalysts and kinetics, are covered in this chapter. Based on the literature, both experimental and theoretical methods are used to explore the ORR kinetics, including reaction processes catalyzed by various electrode materials and catalysts, such as Pt-based alloys, carbon materials, and transition metal macrocyclic complexes. It was emphasized that although there is a large literature on ORR, there is still a need to design materials that can compete with noble metal-containing catalysts for ORR. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.