New Carbon Nanofiber Composite Materials Containing Lanthanides and Transition Metals Based on Electrospun Polyacrylonitrile for High Temperature Polymer Electrolyte Membrane Fuel Cell Cathodes

Abstract

Electrospinning of polyacrylonitrile/DMF dopes containing salts of nickel, cobalt, zirconium, cerium, gadolinium, and samarium, makes it possible to obtain precursor nanofiber mats which can be subsequently converted into carbon nanofiber (CNF) composites by pyrolysis at 1000–1200 °C. Inorganic additives were found to be uniformly distributed in CNFs. Metal states were investigated by transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). According to XPS in CNF/Zr/Ni/Gd composites pyrolyzed at 1000 °C, nickel exists as Ni0 and as Ni2+, gadolinium as Gd3+, and zirconium as Zr4+. If CNF/Zr/Ni/Gd is pyrolyzed at 1200 °C, nickel exists only as Ni0. For CNF/Sm/Co composite, samarium is in Sm3+ form when cobalt is not found on a surface. For CNF/Zr/Ni/Ce composite, cerium exists both as Ce4+ and as Ce3+. Composite CNF mats were platinized and tested as cathodes in high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC). Such approach allows to introduce Pt–M and Pt–MOx into CNF, which are more durable compared to carbon black under HT-PEMFC operation. For CNF/Zr/Ni/Gd composite cathode, higher performance in the HT-PEMFC at I >1.2 A cm-2 is achieved due to elimination of mass transfer losses in gas-diffusion electrode compared to commercial Celtec®P1000.

Deposition of Pt Nanoparticles by Ascorbic Acid on Composite Electrospun Polyacrylonitrile-Based Carbon Nanofiber for HT-PEM Fuel Cell Cathodes

“…It may happen because ascorbic acid is quite acidic due to the ascorbate ion resonance stabilization, therefore, ascorbic acid can coordinate platinum ions and the surface of the composite CNF, leading finally to the better attachment of the Pt nanoparticles to the CNF surface. In our previous studies [26,28], it was shown that Zr and Ni are mostly in forms of ZrO x and Ni 0 in pyrolyzed polyacrylonitrilebased composite CNF. The coincidence of Zr and Pt in addition to Ni on elemental maps may suggest the mentioned mechanism of Pt attachment.…”

“…Earlier [26][27][28][29][30][31][32][33][34][35][36][37][38] we have shown that more durable, compared with carbon black, CNF-based materials, including Pt-Ni-ZrO x /CNF, can be used as cathodes in membraneelectrode assembly (MEA) for HT-PEMFC.…”

Overcoming the Electrode Challenges of High-Temperature Proton Exchange Membrane Fuel Cells

“…ZrO x and Ni(0) introduced into the PGM electrode interact with PA to create more active sites [305]. Carbon nanofiber (CNF) composites doped with Zr/Ni/Gd have been proposed to create phosphate metal species on which the electrode material (Pt) is then deposited [306]. These proton-conducting fillers improve the catalyst layer proton conductivity and hinder acid (PA) leaching.…”

The Role of Electrospun Nanomaterials in the Future of Energy and Environment

“…In another work, Pt-metal/carbon nanofibers and Pt-metal oxide/carbon nanofiber catalytic systems were proposed by Ponomare’s group as gas diffusion electrodes [ 76 ]. Platinated carbon nanofiber (CNF) composites were successfully used as cathodes in the membrane-electrode assembly under high-temperature polymer electrolyte membrane fuel cell experiment.…”