Influence of hot-pressing temperature on the performance of PEMFC and catalytic activity

Abstract

The influence of hot-pressing temperature on catalytic activity and the performance of proton exchange membrane fuel cells (PEMFCs) was investigated using current-voltage (I-V) polarization, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). EIS provided detailed information on the contribution, from high to low frequencies, of internal impedance (R s ), interfacial impedance (R if ) and reaction impedance (R rxn ). The ohmic resistance of the cell (R X ) was estimated from the I-V diagram for comparison with the R s and R if impedances. The R if is useful for diagnosing catalytic activity and interpreting PEMFC performance. A cell was hot-pressed at 125°C (near the transition temperature of Nafion), an optimum temperature for lowest ohmic resistance and total impedance in response to a maximal catalyst-specific activity.

Investigation of Hot Pressed Polymer Electrolyte Fuel Cell Assemblies via X-ray Computed Tomography

“…A wide range of process conditions are reported in the literature with hot press compression pressure ranging from 1380 kPa to 49,000 kPa, temperature from 90 o C to 170 o C, and time of compression from 90 s to 360 s [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][35][36][37][38][39][40][41]. Depending on the materials used, a large number of internal parameters affect the hot-pressing process, which explains why such a wide range of conditions are reported.…”

“…SEM) and electrochemical analysis (electrochemical surface area and impedance spectroscopy) [52]. These studies have shown that the pressing temperature has the most important influence on the bonding process between electrode and electrolyte [2,36,52].…”

“…The hot pressing process [1] bonds together the gas diffusion medium (gas diffusion layer (GDL) / micro-porous layer), the catalyst layer and the electrolyte membrane (usually Nafion) to form the MEA. Compression pressure, time and temperature are the key parameters that determine the product of hot pressing: of these, the temperature is most commonly used to optimise the process [2], typically by a trial and error approach. In spite of the ubiquity of the hot pressing process, little is understood regarding its influence on the resulting MEA structure.…”

Effects of hot pressing conditions on the performance of Nafion membranes coated by ink-jet printing of Pt/MWCNTs electrocatalyst for PEMFCs

“…Three main parameters in the hot-pressing process are temperature (T ), pressure (P), and duration (T ). Typically, the hot-pressing temperature is selected between the glass transition temperature (T g ¼ 115 C) of the Nafion and the decomposition temperature (T d > 280 C) of the Nafion 1100 series of proton-exchange membranes [22,24]. Only at the temperature above T g , the Nafion membrane is softened and can be attached to the electrodes under a high pressure.…”

Impact of Microporous Layer Roughness on Gas-Diffusion-Electrode-Based Polymer Electrolyte Membrane Fuel Cell Performance

“…CCMs are the predominant construction in research studies and are typically found to have better performance. 1,2 Direct coating of CCMs is challenging due to membrane swelling in the catalyst ink solvents. 3 Lab-scale direct-coated CCMs are often fabricated by ultrasonic spray coating where the membrane can be mechanically stabilized on a vacuum plate to prevent shrinking and swelling during the coating process.…”