Abstract
Continuous thin platinum nanoplatelet networks and thin films were obtained on the flat surface of highly ordered pyrolytic graphite (HOPG) by high overpotential electrodeposition. By increasing the deposition time, the morphology of the Pt deposits can be progressively tuned from isolated nanoplatelets, interconnected nanostructures, and thin large flat islands. The deposition is surface-limited and the thickness of the deposits, equivalent to 5 to 12 Pt monolayers, is not time dependent. The presence of Pt (111) facets is confirmed by High Resolution Transmission Electron Microscopy (HRTEM) and evidence for the early formation of a platinum monolayer is provided by Scanning Transmission Electron Microscopy and Energy Dispersive X-rays Spectroscopy (STEM-EDX) and X-ray Photoelectron Spectroscopy (XPS) analysis. The electroactivity towards the oxygen reduction reaction of the 2D deposits is also assessed, demonstrating their great potential in energy conversion devices where ultra-low loading of Pt via extended surfaces is a reliable strategy.
Highlights
Carbon-supported platinum electrocatalysts are employed in the electrodes of Proton Exchange Membrane Fuel Cells (PEMFCs), but due to the scarcity of platinum and its cost [1], efforts to reduce the noble metal loading have driven research towards the development of strategies maximising its utilisation [2], including metal@platinum core@shell nanoparticles [3], platinum nanostructures [4] and thin films [5]
Thin 2D Pt nanoplatelets were grown on electrospun carbon fibres and on nanotubes developed from their surfaces, and the resulting materials were evaluated as electrocatalysts for the Oxygen Reduction Reaction (ORR) in the cathode of a PEMFC, demonstrating enhanced exploitation of the noble metal [15,16]
Such nanofibres and nanotubes do not lend themselves to in-depth investigations using advanced microscopies, and so to further our understanding of this high overpotential electrodeposition method we turned our attention to the model surface of Highly Ordered Pyrolytic Graphite (HOPG), and describe our findings
Summary
Carbon-supported platinum electrocatalysts are employed in the electrodes of Proton Exchange Membrane Fuel Cells (PEMFCs), but due to the scarcity of platinum and its cost [1], efforts to reduce the noble metal loading have driven research towards the development of strategies maximising its utilisation [2], including metal@platinum core@shell nanoparticles [3], platinum nanostructures [4] and thin films [5]. Thin 2D Pt nanoplatelets were grown on electrospun carbon fibres and on nanotubes developed from their surfaces, and the resulting materials were evaluated as electrocatalysts for the Oxygen Reduction Reaction (ORR) in the cathode of a PEMFC, demonstrating enhanced exploitation of the noble metal [15,16] Such nanofibres and nanotubes do not lend themselves to in-depth investigations using advanced microscopies, and so to further our understanding of this high overpotential electrodeposition method we turned our attention to the model surface of Highly Ordered Pyrolytic Graphite (HOPG), and describe our findings. We investigate the effect of a high overpotential single-pulse length on the morphology and crystal structure of the Pt deposits on the flat model carbon surface HOPG for better insights on the deposition mechanism and 2D growth of extended metal surfaces using microscopy and surface analysis techniques
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