Alcohol fuel cells on the horizon
FCs take a hydrogen-rich fuel or hydrogen itself and convert its chemical energy into electrical energy. Proton exchange membrane FCs (PEMFCs) are among the most promising. In the PEMFC, hydrogen gas (H2) is oxidised at the anode to produce protons and electrons. The protons pass through the electrolyte membrane while the electrons are funnelled through an external circuit producing an electrical current. Despite their promise of clean renewable energy, PEMFCs face difficulties related to the storage and transportation of H2. Direct alcohol fuel cells (DAFCs) using ethanol or methanol rather than H2 could overcome the H2 issues. They have been extensively studied over the last two decades for vehicle applications but the low performance and high cost of platinum (Pt)-based catalyst materials for alcohol oxidation at the anode has impeded commercialisation. The EU-funded project XAS-DAFC studied novel nano-structured core-shell catalysts that promise better performance at a lower cost. Instead of a solid Pt nanoparticle, the core-shell structure uses a Pt shell surrounding another metal at its core. Thus, the mass of Pt used is reduced and the opportunity for functionalisation to increase efficiency is introduced. XAS-DAFC characterised the structure/function and stability characteristics of these materials. The team prepared a variety of Pt-based catalysts and used numerous physicochemical techniques to determine their structures and the effects of the second metal on the properties of Pt. Scientists also studied alcohol oxidation activity and stability under electrochemical operating conditions. The most important outcome of the project is that the catalysts are stable under realistic electrochemical conditions and that the presence of alcohol does not affect their structure. Comprehensive testing and characterisation protocol conducted by XAS-DAFC provided a large database of information regarding the behaviours of promising Pt-based catalysts for the oxidation of alcohols in DAFCs. Valuable to future DAFC designs, the catalysts could also speed up commercialisation of these green alternatives to the combustion of fossil fuels.
