Besides cost reduction, durability is the most important issue to be solved before commercialisation of PEM Fuel Cells can be successful. For a fuel cell operating under constant load conditions, at a relative humidity close to 100% and at a temperature of maximum 75 °C, using optimal stack and flow design, the voltage degradation can be as low as 1–2 μV·h. However, the degradation rates can increase by orders of magnitude when conditions include some of the following, i.e. load cycling, start–stop cycles, low humidification or humidification cycling, temperatures of 90 °C or higher and fuel starvation. This review paper aims at assessing the degradation mechanisms of membranes, electrodes, bipolar plates and seals. By collecting long‐term experiments as well, the relative importance of these degradation mechanisms and the operating conditions become apparent.

A pair of interdigitated ultramicroelectrodes (UMEs) is used to electrochemically detect a weak reductor (dopamine) in the presence of a stronger one (K(4)[Fe(CN)(6)]). In the mixture of both reductors, one of the two interdigitated electrodes (the generator electrode) is used to oxidize both species at 700 mV vs. Ag/AgCl, followed by subsequent (selective) reduction of the oxidized dopamine at 400 mV. A regenerated dopamine molecule can thus be oxidized several times (redox cycling) and enable selective detection even in the presence of the stronger reductor. In order to obtain high redox cycling efficiency, we designed and realized platinum electrodes with widths of 2 and 4 microm and spacing of 2 microm, which gave redox cycling efficiencies of 9 and 4 respectively. Using this electrode design, a dopamine/K(4)[Fe(CN)(6)] selectivity of 2 could be obtained.

DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

We present Finite Element Method (FEM) simulations of interdigitated array (IDA) electrode geometries to study and verify redox selectivity and redox cycling amplification factor. The simulations provide an adequate explanation of an earlier found, but poorly understood, high amplification factor (65 Â ) in a 1 mm-spaced IDA microdevice. Moreover, using the FEM calculations we present selectivity measurements with IDA electrodes in a mixture of two redox species, as for example dopamine and ferricyanide. We show that it is possible to electrochemically detect dopamine in presence of the stronger reductor ferricyanide, which is impossible with direct amperometric detection, with the use of IDA electrodes with proper polarization potential of the collector electrode. Using our simulations, we show that a theoretical selectivity of dopamine over ferricyanide of 11 can be achieved.

The electrochemical stability of platinum on carbon catalyst (Hispec™ 4000, Johnson Matthey) has been investigated predominantly at constant potentials ranging from 0.95 to 1.25 V at elevated temperatures. By combining a quartz crystal microbalance (QCM) with electrochemical techniques, dynamic insight is obtained on the oxidation and corrosion of both platinum and carbon during potentiostatic hold. From the cyclic voltammetry (CV) data, it can be concluded that at all conditions, the platinum surface area decreases when Pt on carbon catalysts are exposed to a constant potential of 1.05 to 1.25 V. Under the applied conditions, this loss of surface area is primarily caused by the dissolution of platinum.Both the QCM as well as on‐line electrochemical mass spectrometry (OLEMS) experiments show that the corrosion of carbon is catalysed by the presence of platinum at 80 °C, as long as the platinum surface is not passivated by an oxide layer.