Do not forget the electrochemical characteristics of the membrane electrode assembly when designing a Proton Exchange Membrane Fuel Cell stack

Abstract

International audienceThe membrane electrode assembly (MEA) is the key component of a PEMFC stack. Conventional MEAs are composed of catalyzed electrodes loaded with 0.1-0.4 mgPt cm−2 pressed against a Nafion® membrane, leading to cell performance close to 0.8 W cm−2 at 0.6 V. Due to their limited stability at high temperatures, the cost of platinum catalysts and that of proton exchange membranes, the recycling problems and material availability, the MEA components do not match the requirements for large scale development of PEMCFs at a low cost, particularly for automotive applications. Novel approaches to medium and high temperature membranes are described in this work, and a composite polybenzimidazole-poly(vinylphosphonic) acid membrane, stable up to 190 ◦C, led to a power density of 0.5 W cm−2 at 160 ◦C under 3 bar abs with hydrogen and air. Concerning the preparation of efficient electrocatalysts supported on a Vulcan XC72 carbon powder, the Bönnemann colloidal method and above all plasma sputtering allowed preparing bimetallic platinum-based electrocatalysts with a low Pt loading. In the case of plasma deposition of Pt nanoclusters, Pt loadings as low as 10 g cm−2 were achieved, leading to a very high mass power density of ca. 20 kW g−1 Pt . Finally characterization of the MEA electrical properties by Electrochemical Impedance Spectroscopy (EIS) based on a theoretical model of mass and charge transport inside the active and gas diffusion layers, together with the optimization of the operating parameters (cell temperature, humidity, flow rate and pressure) allowed obtaining electrical performance greater than 1.2 W cm−2 using an homemade MEA with a rather low Pt loading

From hydrogen production by water electrolysis to its utilization in a PEM fuel cell or in a SO fuel cell: Some considerations on the energy efficiencies

“…For the PEM hydrogen-oxygen fuel cell, the working cell voltage at 25 C is typically 0.72 V at 1 A cm À2 [18], which leads to: For a SOFC working at e.g. 800 C a cell voltage E cell ¼ 0.5 V is obtained at a current density of 0.4 A cm À2 whereas an Open Circuit Voltage, E(j ¼ 0) ¼ 0.86 V, is measured [19], leading to a voltage efficiency ε E ¼ 0.5/0.86 ¼ 58.1%.…”

Advanced catalytic layer architectures for polymer electrolyte membrane fuel cells

“…Another important feature of such catalysts is the depth of the Pt concentration profile in the electrode, which can be controlled by adjusting the deposition parameters and the plasma source. These techniques offer organized thin film structures composed of regular arrays of several hundreds of nm carbon pillars covered by Pt . Similar to the case of NSTFs, sputtered catalytic layers may be employed without Nafion ® ionomer.…”

“…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 .…”

Evaluation of Nafion with Various Pt–C Concentrations in Membrane Electrode Assemblies for PEMFCs

“…The membrane electrode assembly (MEA) is the most important part of a polymer electrolyte membrane fuel cell (PEMFC) . The electrochemical reaction technically takes place in the MEA, where hydrogen is oxidized at the anode and oxygen is reduced at the cathode.…”