Highly Efficient Nanostructured Hybrid Catalysts for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells
Authors: Yarar Kaplan Begüm , Haghmoradi Navid , Biçer Emre , Merino César , Alkan Gürsel Selmiye 
Published: February 2020

Among the other type of fuel cells, polymer electrolyte membrane fuel cell (PEMFC) is one of the most attractive renewable energy sources due to its pollution-free operation in transportation, high efficacy, and compact structure [1]. Although PEMFC has numerous advantages, durability and cost are the primary challenges to its commercialization. Catalyst and catalyst support play essential roles for to reduce the cost, improve the durability, and performance of the PEMFC. Platinum (Pt), and Pt containing alloys have been extensively used as catalyst. However, Pt is very expensive and performance of PEMFC strongly depends on its utilization. Moreover, carbon black (CB) has been commonly used catalyst support since it is inexpensive and readily available yet it has various drawbacks (not corrosion resistant, contains deep cracks and mesopores, etc.) cause to decline of activity and performance of the catalyst. Additionally, conversion of fuel chemical energy of the fuel in a PEMFC is predominantly limited by slow kinetics of the oxygen reduction reaction (ORR) on the catalyst surface. Recently, hybrid carbon structures widely have been investigated as alternative catalyst support materials. Two-dimensional (2D) graphene [2] and 1D nanostructures of carbon such as nanotubes (CNTs) and nanofibers (CNFs) [3] have been investigated as catalyst supports, due to their exciting properties such as anisotropy, good electronic conductivity, high surface area and chemical stability.
Here, we reported the development of catalysts for fuel cell reactions based on Pt nanoparticles supported on hybrid carbon support networks comprising highly conducting carbon nanofibers (CNFs) and CB (Vulcan-XC-72). By means of a rapid and efficient microwave assisted synthesis, Pt nanoparticles were deposited on various hybrid carbon structures. Hybrid carbon supports provide not only the superior Pt utilization but also better GDE porosity, and conductivity. Resultant catalysts were investigated by X-ray Diffraction (XRD), X-Ray photoelectron spectroscopy (XPS) and Transmission Electron Microscopy (TEM) techniques for their structure and morphology. The uniformly dispersed Pt nanoparticles on hybrid carbon support with a small particle size (2-3 nm) were obtained. Electrocatalytic activity of prepared electrocatalysts towards fuel cell reactions (HOR and ORR) were investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The hybrid electrocatalyst was exhibited superior HOR and ORR catalytic activities by enhanced utilization of Pt. Moreover, gas diffusion electrodes and membrane electrode assemblies are fabricated by using synthesized electrocatalysts and tested in the PEMFC.

References:

[1] G. J. K. Acres, J. Power Sources, 100 (2001) 60–66.
[2] L. Işıkel Şanlı, V. Bayram, B. Yarar, S. Ghobadi, S. Alkan Gürsel, Int. J Hydrogen Energy, 41 (2016), 3414-3427.
[3] S. A. Grigoriev, V. N. Fataev, E. K. Lutikova, A. S. Grigoriev, D. G. Bessarabov, X. Wei, J. Ge, Int. J. Electrochem. Sci., 11 (2016) 2085-2096.