Fuel cell technology is currently shifting very fast from fundamental research to real development. In addition to other aspects, this transition is possible because of the important improvements achieved in the field of electrocatalysis in the past decade. This perspective will give a focused overview summarizing the most outstanding contributions in the last 10 years in terms of activity and durability of the catalyst materials for ethanol oxidation and oxygen reduction reaction, respectively. In addition, it provides an outlook about new catalyst support materials with improved performance/stability, advanced characterization techniques, and fundamental studies of reaction mechanisms and degradation processes. All the studies referred to in this perspective significantly contribute to reaching the technical targets for PEFC commercialization.

The catalytic activity and selectivity of Pt nanoparticles towards the oxygen reduction reaction (ORR) were investigated as a function of the Pt catalyst distribution. By means of the sputtering deposition technique, it was possible to fabricate Pt catalysts with different loadings that consisted of dispersed 2–3 nm particles, nanoparticle agglomerates and extended particulate layers. The transition from dispersed nanoparticles to extended layers led to a decrease in the electrochemical surface area (ECSA, m2Pt gPt−1) and to a shift of the platinum oxide reduction peak to more positive potentials, which indicates a decrease in the adsorption energy for oxygenated species. The latter finding was correlated to the observed decrease in specific activity with the increasing ECSA, that is, in the case of isolated nanoparticles, the higher adsorption energy for oxygenated species causes a reduction in the specific activity towards the ORR as larger amounts of active sites are blocked compared to extended surfaces. The presented data of specific and mass activity versus ECSA were found to follow a “master curve” obtained by comparing normalised Pt activities from different studies. The transition from dispersed Pt nanoparticles to extended layers also influences the Pt selectivity. At a decreased interparticle distance, a significant increase in the H2O2 production was observed below 0.6 V versus the reversible hydrogen electrode, which indicates the important role of a H2O2 desorption–readsorption reaction mechanism during the ORR on Pt nanoparticles.

In this work, high surface area antimony doped tin oxide (Sb-SnO2) has been synthesized using a modified sol-gel synthesis method. The bulk and surface properties of the metal oxide support have been investigated as a function of the processing conditions. A change in the Sb-SnO2 processing conditions, while preserving an overall invariant bulk composition, led to substantial modification of the surface stoichiometry. Accelerated stability test protocols have shown that the surface composition represents a crucial parameter for the electrochemical stability of Sb-SnO2. Model Pt/Sb-SnO2 electrodes have been developed depositing Pt nanoparticles by magnetron sputtering on the optimized Sb-SnO2 porous surface. A significant enhancement in the corrosion stability upon 1000 potential cycles between 0.5 and 1.5 V (RHE) at 50 mV s(-1) has been observed for the Pt/Sb-SnO2 system compared to Pt/carbon.

The level of Pt loadings in polymer electrolyte fuel cells (PEFC) is still one of the main hindrances for implementation of PEFCs into the market. Therefore, new catalyst and electrode preparation methods such as sputtering are of current interest, because they allow thin film production and have many cost saving advantages for electrode preparation. This paper summarises some of the most important studies done for sputtered PEFCs, including non carbon supported electrodes. Furthermore, it will be shown that an understanding of the main morphological differences between sputtered and ink-based electrodes is crucial for a better understanding of the resulting fuel cell performance. Especially, the electrochemical surface area (ECSA) plays a key role for a further increase in PEFC performance of sputtered electrodes. The higher surface specific activities i(k,spec) of sputtered compared to ink-based electrodes will be discussed as advantage of the thin film formation. The so- called particle size effect, known in literature for several years, will be discussed as reason for the higher i(k,spec) of sputtered electrodes. Therefore, a model system on a rotating disc electrode (RDE) was studied. For sputtered PEFC cathodes Pt loadings were lowered to 100 μg(Pt)/cm(2), yet with severe performance losses compared to ink-based electrodes. Still, for Pt sputtered electrodes on a carbon support structure remarkably high current densities of 0.46 A/cm(2) at 0.6 V could be achieved.