Increasing the efficiency of electrocatalyst is the key demand for the polymer electrolyte membrane fuel cells (PEMFC). To address the activity and performance challenges of commercial electrocatalyst, Pt/C, we introduce a new hybrid catalyst support for Pt nanoparticles. In this regard, combining or mixing specific type of carbon-based supports is a feasible strategy to increase catalyst utilization and performance. In the current study, Pt nanoparticles (NPs) were decorated on a new hybrid network, comprising of carbon nanofiber (CNF) and carbon black (CB), by means of a facile and efficient microwave (MW) assisted reduction method. All synthesized electrocatalysts were characterized to elucidate chemical and morphological structures. Then, the hybrid electrocatalysts were utilized as hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) electrocatalysts and their electrocatalytic activities were investigated by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), respectively. We found that the hybridization of CNF with CB substantially improved not only the electrocatalytic activity but also the fuel cell performance, which can be attributed to a consecutive conductive network, in which CB acts as a spacer, and synergistic effects between the CNF and CB. The hybrid electrocatalyst (Pt/CNF-CB with 50:50 wt%) showed a superior activity toward HOR and ORR while also offering exceptional fuel cell performance. That hybrid possessed the highest electrochemically active surface area (ECSA) compared with Pt/CNF and Pt/CB. In addition, the mass activity (at 0.80 V vs RHE) of the Pt/CNF-CB (50:50 wt%) is about 3.3 and 3.5 times higher than that of Pt/CNF and Pt/CB, respectively. Furthermore, that hybrid electrocatalyst exhibited enhanced fuel cell performance with 907 mW. cm −1 maximum power density. This work demonstrated that the CNF-CB supported Pt nanoparticles as electrocatalysts are extremely promising for fuel cell reactions.

Graphene with its two-dimensional structure and unique properties has immense potential in energy-related applications such as proton exchange membrane (PEM) fuel cells. Herein, we employ a well-known biomolecule arginine-glycine-aspartate (RGD) peptide-functionalized graphene-supported Pt nanoparticles as an electrocatalyst for PEM fuel cells for the first time. First, chemically reactive graphene oxide (GO) is used as a precursor to covalently functionalize it with RGD peptide through amide bond formation. The amino moieties of RGD peptide on graphene surface serve as ligands and active sites for the nucleation and controlled growth of Pt nanoparticles through polyol reduction method. The homogeneous distribution of ultra-small (about 3 nm) Pt nanoparticles supported on RGD functionalized graphene boosted the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) electrocatalytic activities by 52% in electrochemical active surface area (ECSA), 112% in mass activity, and 39% in specific activity as compared to unmodified graphene surface. The strong interaction between the metal and the modified support's surface, assisted in evading serious agglomeration and dissolution during 1000 cycles of accelerated degradation tests (ADT), improving the longterm durability of the Pt electrocatalyst by showing about 21% higher ECSA retention than the unmodified support. Fuel cell performance of RGD functionalized graphene-supported Pt nanoparticles also depicted improved power output due to its better Pt utilization and electrocatalytic activity.

Y akıt pilleri elektrik üretimi için kullanılabilecek en verimli enerji çevrim sistemlerinden biri olarak kabul edilmektedir. Polimer elektrolit membranlı yakıt pilleri ve anyon değişim membranlı yakıt hücreleri için hem ayraç hem de elektrolit olarak katı iyon iletken bir polimer membran kullanılmaktadır. Radyasyonla aşı polimerizasyonu, ticari polimer membranlar için düşük maliyetli alternatiflerin üretimi için kullanılan çok yönlü bir yöntemdir. Bu yöntemde, tipik olarak bir baz polimer, polimer substrat içinde aktif radikal bölgeleri oluşturan iyonlaştırıcı radyasyona maruz bırakılır. Ardından uygun bir vinil monomeri bu aktif bölgeler üzerinde polimerleştirilir. Son aşama olarak, hidrofobik polimer çatısına hidrofilik grupların eklenerek iyon iletken bir membran oluşturulması için son bir kimyasal işlem yapılır. Radyasyonla aşılama parametrelerinin membran özelliklerine etkisi konusunda çeşitli çalışmalar vardır. Ayrıca, bu tür radyasyonla aşılanmış membranların, yakıt pili ile ilgili elverişli özellikleri ve polarizasyon özellikleri rapor edilmiştir. Bu nedenle, radyasyonla aşılanmış polimer membranlar, yakıt pilleri için önemli düşük maliyetli alternatiflerden biridir. Bu derleme, radyasyonla aşılanmış membranların hazırlanması, yakıt pili ile ilgili özelliklerinin ve yakıt pili performanslarının karakterizasyonlarına odaklanmaktadır.

Polymer electrolyte membrane (PEM) fuel cells are attractive for various applications due to their high efficiency and low operation temperatures. Platinum (Pt) nanoparticles, used as catalyst in PEM fuel cells, have high cost, performance and durability problems; and low abundance. Catalyst support materials are of great importance in regulating the properties of catalyst nanoparticles such as shape, size, and dispersion. Carbon black, the most commonly used commercial catalyst support, has several limitations which cause the degradation of catalyst activity and performance. Graphene, as a unique single-atom thick layered structure of carbon, possesses excellent electrical, thermal and mechanical properties. Moreover, the previous reports have revealed that graphene and its derivatives could be used as highly efficient electrodes in various energy related applications. However, the ultimate extent of graphene based materials in energy applications, especially in fuel cells, is yet not to be found. In addition, the crucial role of graphene-based materials in providing the reliable solid-state support for platinum nanoparticles for fuel cells should be noted [1]. In the present work, various graphene based materials including graphene oxide (GO), graphene nanoplatelets, functionalized graphene and graphene hybrids have been utilized as the catalyst support [1]. Graphene supported Pt nanoparticles were synthesized by means of impregnation-reduction, microwave-assisted deposition and photocatalytic deposition methods. Well dispersed and uniformly decorated Pt nanoparticles with a small particle size (2-3 nm) on graphene and its derivatives are obtained by impregnation-reduction and microwave-assisted deposition methods [2]. Moreover, substantially enhanced electrocatalytic activity and fuel cell performances for graphene-based electrocataalysts, compared to commercial carbon black based systems, were achieved. Furthermore, the use of graphene hybrids as the catalyst support resulted in a significant improvement in both catalytic activity and catalyst utilization in PEM fuel cells. In addition, we have successfully modified the electronic band structure of the GO and we achieved a scalable and precisely controlled synthesis of sub-nanosized Pt on reduced GO by photocatalytic deposition [3]. References 1. E. Quesnel, F. Roux, F. Emieux, P. Faucherand, E. Kymakis, G. Volonakis, F. Giustino, B. Martín-García, I. Moreels, S. Alkan Gürsel, et al., ‘Graphene-based technologies for energy applications, challenges and perspectives’ 2D Mater., 2, 030204 (2015). 2. B.Y. Kaplan, N. Haghmoradi, E. Biçer, C. Merino, S. Alkan Gürsel, ‘High performance electrocatalysts supported on graphene based hybrids for polymer electrolyte membrane fuel cells’ Int. J. Hydr. Energy, 43, 23221(2018). 3. S. Abdolhosseinzadeh, S. Sadighikia, S. Alkan Gürsel, ‘Scalable synthesis of sub-nanosized platinum-reduced graphene oxide composite by an ultra-precise photocatalytic method’ ACS Sustainable Chem. Eng. 6, 3773 (2018).

Graphene nanomaterials are increasingly important with their distinct properties such as high electrical conductivity, high contact surface area and enormous stability. Therefore, graphene has been used as promising catalyst support in energy conversion and storage systems. In order to achieve high catalytic activity a specifically guided growth of catalyst on graphene support surface with delicate controllability is highly preferred. Therefore, we modify graphene surface in two different ways such as graphene functionalization with various active functional groups and fabrication of nanocomposites with intrinsically conducting polymers e.g. polypyrrole (PPy). We have successfully modified graphene oxide by the functionalization with free amine groups (GO-NH2), RGD peptide (GO-RGD) and Nitrogen doping (N-GO). Platinum (Pt) catalyst nanoparticles have been deposited on these functionalized GO (f-GO) using ethylene glycol modified method. The dispersion of Pt deposited F-GO has been enhanced and stable optimized dispersions in organic solvents were obtained. The cyclic voltametry (CV) results showed a high electrochemical surface area (ECSA) of 147 m2/g for GO-RGD compared to Pt/carbon black (Pt/C, 80 m2/gPt) and Pt/GO (99 m2/gPt). On the other hand, we also fabricated GO/PPy/CB (carbon black) hybrid nanocomposites as catalyst support and deposited Pt catalyst nanoparticles. The CV results showed a high ECSA of 153 m2/gPt. These modified graphene nanomaterials including Pt/f-GO and hybrid composites have been successfully used in proton exchange membrane fuel cell (PEMFC) electrodes. The Pt nanoparticles distribution on various modified graphene surfaces, which may significantly influence their properties such as electrical conductivity, electrocatalytic activity when they used as catalyst support and fuel cell performance will be discussed more in details.