Enhancing the activity of platinum:  investigating the effects of alloyed, strained and nanostructured fuel cell electrocatalysts

In this article-based thesis, we investigate the synthesis and characterisation of Pt-based electrocatalysts for fuel cell electrodes. The aim of this research is to enhance the electrocatalytic activity of pure Pt by modifying it in the following ways: combining it with a second metal; applying strain; and nanostructuring. This thesis comprises six journal articles that further the understanding of enhanced catalytic activity by providing new physical insight into the electrochemical processes that occur on fuel cell electrodes.

Combining Pt with a second metal can enhance electrocatalytic activity while reducing the amount of Pt required for a variety of processes. We use magnetron sputtering to deposit Fe-Pt alloy thin films and investigate their activity as electrocatalysts for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). Bimetallic Pt-Au film electrocatalysts were synthesised and investigated for the formic acid oxidation reaction (FAOR).

Inducing strain in a Pt electrocatalyst is known to increase its activity for methanol oxidation, however up until now the reason for this was unclear. In this study, we use electroless deposition to grow thin films of Pt with varying thickness and investigate the effect of strain on MOR activity. We find a direct relationship between the amount of compressive strain and the methanol surface coverage of the Pt electrocatalysts. This original contribution to knowledge clarifies the role of strain in enhancing the MOR.

Electrocatalytic nanostructures grown in this research exhibit high activity and durability for methanol oxidation due to their high surface area, specific morphology and exposed crystal facets. In this study, we use electroless deposition to grow an interconnected network of Pt and Fe-Pt nanotubes and obtain maximum MOR activity of 1.43 mA cm-2 and 21.4 mA cm-2 in acidic and alkaline media, respectively.