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The electrodeposition of Pt nanoparticles (NPs) on two-dimensional single walled carbon nanotube (SWNT) network electrodes is investigated as a means of tailoring electrode surfaces with a well-defined amount of electrocatalytic material. Both Pt NP deposition and electrocatalytic studies are undertaken using the microcapillary electrochemical method (MCEM), enabling multiple microscale measurements to be performed quickly and easily on the same SWNT sample. Using this approach, Pt catalysts with high specific surface areas relative to the geometric electrode area (defined by the meniscus contact of the MCEM probe with the Si/SiO 2 substrate bearing the SWNT network) can be controlled precisely over three orders of magnitude. This enables the influence of the specific surface area of an electrocatalyst on activity to be investigated, as demonstrated by studies of the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). [ABSTRACT FROM AUTHOR]

• Operando synchrotron X-ray study on Phosphorus and Platinum migration. • Graphene-related-material applied as interventional materials for comparison. • X-ray Absorption Near Edge Structure applied to study chemical structural change. • Conducting mechanistic studies via the three-phase interface. • Performance and durability of high-temperature proton exchange membrane fuel cells. The application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) addresses challenges in water management, fuel purity, and overheating under high current density. However, phosphoric acid (PA) migration hinders their development. This study uses synchrotron-based X-ray fluorescence spectroscopy to investigate PA and catalyst migration. Interventions with single-layer graphene and electrochemically exfoliated graphene oxide improve performance and durability. X-ray absorption spectroscopy provides insights into relevant mechanisms, advancing understanding of membrane electrode assembly preparation and the intricate influences of PA and catalyst migration on performance and durability in HT-PEMFCs. [ABSTRACT FROM AUTHOR]