Cracking of nanofilm-based devices for electrochemical energetics

Fabrication and testing of fuel-cells based on nanofilm electrodes and interconnects is a hot technological challenge for three key reasons: (i) miniaturisation and integration into electronic devices as well as implementation of on-chip logics, (ii) testing of the performance of nano-materials on their real scale and (iii) use of cuttingedge material characterisation techniques. The principal interest of a nanotechnological approach to material problems in electrochemical energetics is particularly related to long-term durability issues of critically degradable components. Among the degradation modes, mechanical failure by cracking of the functional thin films is being recognised as a crucial one, impairing the implementation of laboratory systems into real-life devices. In this paper we report on corrosion-induced local thinning and correlated cracking of electrode components in a RTIL-based Proton Exchange Membrane Fuel Cell with Pt micro-particles as catalyst, Au feeder electrodes and Fe interconnects. In situ imaging of the multi-material system in electrochemical environment, based on X-ray scanning and optical microscopies, has disclosed the formation of complex cracking patterns, including spiral cracks. A simple mechanical explanation of the peculiar cracking pattern is proposed.