Effect of platinum loading on fuel cell cathode performance using hydrocarbon ionomers as binders

Abstract

The effect of platinum loading on cathode performance in hydrogen/oxygen fuel cells was investigated using perfluorosulfonic acid (Nafion), sulfonated polyimide (SPI-8) and sulfonated poly(phenylene ether ether ketone) (SPEEK) ionomers as the electrode binder. By lowering the platinum loading, the cathode polarization decreased for MEAs using SPI-8 and SPEEK binders at high humidity (90-100% RH (relative humidity)) due to an improvement of mass transport (oxygen supply and/or water discharge) in the catalyst layer. In contrast, at humidity lower than 80% RH, the effect of platinum loading on the cathode performance differed between these two hydrocarbon (HC) ionomers. When SPI-8 was used as the binder, the cathode polarization increased when lowering the platinum loading due to an increase of activation overpotential. When SPEEK was used as the binder, the effect of platinum loading on the cathode performance was smaller. Such differences can be ascribed to the specific adsorbability of these hydrocarbon binders on the platinum catalyst at low humidity. These results point to crucial factors in achieving higher performance at low platinum loadings and low humidity using HC binders.

Effect of Electronic Conductivities of Iridium Oxide/Doped SnO₂ Oxygen-Evolving Catalysts on the Polarization Properties in Proton Exchange Membrane Water Electrolysis

“…The Rohm, cell of the conventional cell in Table 2 was just mΩ cm 2 , which is assumed to include Rohm, anode (IrO2 + Pt black) and Rohm, cathode (Pt black), together with contact resistances with the gas diffusion layers (Pt/Ti mesh and carbon paper, see Materials and Methods). This value of Rohm, cell agrees precisely with those of polymer electrolyte fuel cells (PEFCs) with Nafion ® membrane of the identical thickness and Pt/C catalysts for the anode and cathode [39][40][41]. Thus, by adding the Rohm, anode of IrOx/M-SnO2 to 75 mΩ cm 2 stated above, we calculated the Rohm, cell, calc values to be 78, 143, and 1408 mΩ cm 2 , for the cells with IrOx/Sb-SnO2, IrOx/Ta-SnO2, and IrOx/Nb-SnO2, respectively.…”

Effect of Electronic Conductivities of Iridium Oxide/Doped SnO2 Oxygen-Evolving Catalysts on the Polarization Properties in Proton Exchange Membrane Water Electrolysis

“…The R ohm, cell of the conventional cell in Table 2 was just 75 mΩ cm 2 , which is assumed to include R ohm, anode (IrO 2 + Pt black: the electronic conductivity of IrO 2 powder is very high [37]) and R ohm, cathode (Pt black), together with contact resistances with the gas diffusion layers (Pt/Ti mesh and carbon paper, see Materials and Methods). This value of R ohm, cell agrees precisely with those of polymer electrolyte fuel cells (PEFCs) with Nafion ® membrane of the identical thickness and Pt/C catalysts for the anode and cathode [46][47][48]. Thus, by adding the R ohm, anode of IrO x /M-SnO 2 to 75 mΩ cm 2 stated above, we calculated the R ohm, cell, calc values to be 78, 143, and 1408 mΩ cm 2 , for the cells with IrO x /Sb-SnO 2 , IrO x /Ta-SnO 2 , and IrO x /Nb-SnO 2 , respectively.…”

Benzene Adsorption: A Significant Inhibitor for the Hydrogen Oxidation Reaction in Alkaline Conditions

“…The results from this research suggest that the HEMFC performance with properly designed electrode materials can demonstrate excellent performance that is even superior to PEMFC performance, as reported by others. 5,6 The results from this research may also be applicable to other fuel cell systems, such as phosphoric acid-doped high-temperature polymer electrolyte membrane fuel cells 52,53 and low-temperature polymer electrolyte membrane fuel cells using polyaromatic electrolytes, 54 which showed relatively poor performance by the possible adsorption of the aromatic moiety onto the Pt surface. Further studies regarding the effect of benzene concentration, substituents, and other aromatic or heterocyclic compounds with π electrons are needed for a more precise interpretation of the acidic fuel cell performance in the presence of benzene adsorption.…”