ABSTRACT
The trio of exhaustible fossil energies, increasing carbon dioxide emissions, and the effects of global warming calls for the implementation of new technologies for energy conversion and storage. Among these, fuel cells are electrochemical devices directly converting the chemical energy of a fuel and an oxidant into electricity and heat. Their core, the so-called membrane electrode assembly (MEA), consists of two electrodes in contact with an electrolyte conducting only ionic species (Figure 2.1). At the anode, the fuel is decomposed into ions and electrons. There are several kinds of fuel cells, working in different conditions and with different fuels and, consequently, based on different materials1 (see also Chapter 3). Depending on the type of cell,
2.1 Introduction ....................................................................................................29 2.2 Nanostructured Composite Ionomer Membranes ........................................... 31
2.2.1 Composite Membranes with the Ionomer Embedded in a Reinforcing Electrospun Mat .............................................................. 32
2.2.2 Composite Membranes with an Inert Polymer Embedded in an Ionomer Electrospun Mat .......................................................... 35
2.3 Electrospun Electrocatalyst Supports ............................................................. 39 2.3.1 Carbon-Based Supports ...................................................................... 41 2.3.2 Noncarbon Supports ........................................................................... 43 2.3.3 Composite Supports ............................................................................ 45
2.4 Self-Supported Electrocatalysts ...................................................................... 47 2.5 Electrospun Electrode Components ...............................................................50 2.6 Conclusions and Future Challenges ................................................................50 References ................................................................................................................ 51
the ionic species travel from the anode to the cathode or vice versa, while electrons travel along an external circuit to the cathode, where oxygen reduction takes place (Figure 2.1). Fuel cells are a reliable and environmentally friendly method to produce energy with higher conversion efciencies than any other conventional thermomechanical system. Indeed, when operating with hydrogen as the fuel, they produce only water, providing a clean mechanism for energy conversion. Furthermore, hydrogen can be produced by renewable energy sources (wind, solar, biomass, etc.), positively impacting the sustainable development and energy security. Hydrocarbon fuels such as low molecular weight alcohols and bioalcohols can also be used as renewable fuel source. Despite the consequent production of carbon dioxide, these systems have a real importance for portable electronics applications. The intrinsic modularity of fuel cells in stacks allows for simple fabrication and a wide range of applications in portable, stationary, and transportation power generation.
