Catalyst synthesis techniques

Abstract

This chapter deals with aspects of the synthesis of fuel cell catalysts. Practical catalysts for low-temperature fuel cells are typically in the nano-size range and are frequently formed or deposited on high-surface-area supports. Pt is the most commonly used catalyst for both cathode and anode in proton exchange membrane fuel cells (PEMFCs). In the case of the cathode, combined catalyst systems such as Pt nanoparticles supported on Au or Pt alloy catalysts, as well as Pt-skin catalysts formed in combination with the iron group metals have also attracted attention. Much work has been carried out on the development of non-noble metal (Pt-free) catalysts, the synthesis of which will be discussed in Section 9.5. In the case of the anode, bi-metallic catalysts are typically employed unless the fuel is neat H2. Pt-Ru is the state-of-the-art catalyst for both methanol and reformate fuel cells. For the latter, other anode catalysts such as Pt/MoOx and Pt/Sn are also considered promising. In this chapter we present an overview of methods used to synthesize fuel cell catalysts, with a focus on catalysts for PEMFCs and direct methanol fuel cells (DMFCs). Examples for the synthesis of catalysts for other low-temperature fuel cells, such as formic acid, are not included in this chapter. The synthesis of both Ptbased and Pt-free catalysts is discussed, and dedicated sections describe methods that allow control of catalyst size and composition. First, general catalyst synthesis methods are introduced. Subsequently, the reader is introduced to particle size and " structure" control of fuel cell catalysts. © 2008 Springer-Verlag.