Advanced catalytic layer architectures for polymer electrolyte membrane fuel cells

Fuel cell current–voltage and current–power characteristics obtained with Pt/VACNT layers at the cathode: (a) effect of the area density of VACNTs (9 × 6, 5 × 6, and 3 × 6 mL correspond to the density of 9.0 × 10¹⁸, 4.8 × 10¹⁸, and 3.6 × 10¹⁸ cm⁻², respectively), (b) effect of the Nafion content in the Pt/VACNF film, (c) effect of the Pt loading in the Pt/VACNF, (d) comparison of Pt/VACNTs with Johnson Matthey 40 wt% Pt/C. Single fuel cell tests were performed at 80 °C with humidified H₂/O₂ (dew point temperature of 80 °C and 70 °C, respectively) under a back pressure of ca. 200 kPa. F–20 µg cm² B–15 µg cm² means that Pt was deposited on both sides of VACNTs with Pt loading of 20 µg cm⁻² on the front side and 15 µg cm⁻² on the back side. (Reproduced with permission from Ref . Copyright 2011 Wiley‐VCH)

Schematic representation of the Pt/VACNT preparation and integration into a membrane‐electrode assembly of a PEMFC. (Reproduced with permission from Ref . Copyright 2006 The Electrochemical Society)

Pt surface area normalized ORR (a) and H₂O₂ escape (b) currents measured in the O₂ saturated 0.1 M H₂SO₄ electrolyte on Pt/VACNF electrodes with various Pt loadings at different electrode potentials vs. their electrochemically active surface area. ORR currents are not corrected for mass transport losses. The lines are guides for the eye. (Reproduced with permission from Ref . Copyright 2012, Elsevier)

VACNF layer on Si(1 0 0) substrate (a) before and (b) after Pt deposition realized by in situ reduction of H₂PtCl₆·6H₂O with ascorbic acid within the VACNF layer.

Schematics representing the steps involved in the preparation process of Pt/VACNF catalytic layers on TiO_x/Ti rod for model rotating ring disc electrode studies. (Reproduced with permission from Ref . Copyright 2012, Elsevier)

SEM micrographs of vertically aligned CNTs/CNFs grown by different approaches (a) CCVD from a toluene–ferrocene mixture. (Reproduced with permission from Ref . Copyright 2010 Elsevier); (b) Plasma‐assisted CCVD, (Reproduced with permission from Ref . Copyright 1998, American Institute of Physics); (c) CCVD on a micro‐patterned substrate, (Reproduced with permission from Ref . Copyright 1999 American Institute of Physics); (d) CVD in a porous alumina membrane, (Reproduced with permission from Ref . Copyright 2013, Elsevier)

PEM fuel cell polarization curves for co‐sputtered PtC electrodes at a Pt loading of 0.01 mg cm⁻². Flow rates O₂ = 0.35 sccm, H₂ = 0.5 sccm, P_O2 = 380 kPa, P_H2 = 310 kPa, T_O2 = 40 °C, T_H2 = 80 °C, T_cell = 80 °C. Nafion 212 membrane. (Reproduced with permission from Ref . Copyright 2009 Elsevier)

Comparison of the activity and stability of NSTFs with those of conventional Pt/C catalysts. (a) Current–voltage characteristics (inset) and mass activities measured in a H₂/O₂ PEMFC at 80 °C. (Reproduced with permission from Ref . Copyright 2003 John Wiley and Sons, Ltd) (b) Evolution of the electrochemically active surface area of Pt with the number of potential cycles in the interval from 0.6 to 1.2 V at different temperatures as indicated in the figure. (Reproduced with permission from Ref . Copyright 2006 Elsevier)

Specific (solid bars) and mass (hatched bars) ORR activities measured in HClO₄ 0.1 M at 0.9 V and 293 K for various Pt‐based materials. Data for Pt/C, polycrystalline Pt/NSTF, PtNi₂/NSTF, and Pt₃Co/NSTF are adapted from Ref. Data for Pt/Nb₂O₅ prepared by GLAD and Pt₃/VACNF are extracted from Refs and , respectively.

Principal directions for the development of ordered nanostructured catalytic layers for PEMFCs. SEM micrographs of (a) conventional Pt/C‐based catalytic layer ordered under the influence of strong electric field, (Reproduced with permission from Ref . Copyright 2002 Elsevier) (b) NSTF catalytic layers, (Reproduced with permission from Ref . Copyright 2006 Elsevier) (c) Carbon/Pt layers produced by plasma sputtering, (Reproduced with permission from Ref . Copyright 2011 Elsevier) (d) Vertically aligned carbon nanofiber layer grown on TiO_x/Ti/Si(1 0 0) using catalytic chemical vapor deposition, (Reproduced with permission from Ref . Copyright 2010, Elsevier) (note that the top part of the layer was sheared to better expose the structure). (e) Carbon nanotubules grown in a porous alumina membrane after dissolution of the latter. (Reproduced with permission from Ref . Copyright 1998 Nature) (f) N‐doped vertically aligned carbon nanotubes, (Reproduced with permission from Ref . Copyright 2012, Elsevier) (g) Nb oxide film on a Si wafer prepared by the glancing angle deposition (GLAD), (Reproduced with permission from Ref . Copyright 2012 Elsevier)

Simulated mass transport limited current densities and Pt loading per unit electrode area as a function of the pore size (spacing) in the VACNT structure. The CNT length was kept constant at 10 µm and the Nafion film thickness was maintained at 1 µm for all cases. (Reproduced from Ref . Copyright 2008 Elsevier)

Polarization and power density curves calculated for a conventional active layer and an ordered active layer models and compared to the experimental data for a conventional Pt/C catalytic layer. Inset: Percentage of the performance improvement for ordered with respect to the conventional layers. (Reproduced with permission from Ref . Copyright 2008 Elsevier)