Palladium-Based Nanostructured Electrocatalysts for Fuel Cells: Design, Activity and Durability

The development of fuel cell technology based on low temperature has been accelerated by the discovery of Pd as a cheap and abundant alternative to Pt; with good catalytic activity for the alcohol oxidation reaction and acceptable properties for oxygen reduction reaction (ORR) in alkaline conditions; further enhanced by its unique resistance to carbon monoxide poisoning and ability to quickly produce hydroxyl species on its surface. However, despite all this progress there remains significant knowledge gaps. Many reports about the activity of Pd based electrocatalysts overestimate the activity of the material due to the fact that they used very low metal loadings and expressed the normalized current density per mass of the metal. Furthermore, many of the methods employed to increase the activity of the material when tested as a half-cell failed to be translated into real world application when tested as membrane-electrode assemblies. In this review article we evaluate the status of the field of Pd electrocatalysis for both alkaline fuel cells and alcohol oxidation reactions. We provide an evaluation of the areas in which Pd excels, and in which it falls short of Pt. We also evaluate the various approaches that are being taken to create Pd based electrocatalysts that can be applied to practical devices. This review should provide direction for researchers working towards developing Pd electrocatalysts that can be demonstrated to work effectively under conditions representative of real-world fuel cell applications, and that will ultimately help to advance the conversion of chemical energy to electrical energy in a sustainable manner.