Electrochemical performance of fuel cell catalysts prepared by supercritical deposition: Effect of different precursor conversion routes

• Pt/Vulcan electrocatalysts were prepared using supercritical deposition (SCD).
• Effects of various conversion routes on the physical and electrocatalytic properties were evaluated.
• PEMFC performance of Pt/Vulcan catalysts prepared using SCD was reported for the first time.
• Catalyst via thermal conversion at ambient pressure had the best performance.
• Peak power density of 190 mW cm−2 and Pt utilization of 380 mW mgPt−1 were obtained.

Supercritical deposition (SCD) is used to prepare carbon-supported Pt nanoparticles as electrocatalysts for proton exchange membrane fuel cells (PEMFCs). Dimethyl(1,5-cyclooctadiene)platinum(II) (Pt(cod)me2) is adsorbed from supercritical carbon dioxide (scCO2) solutions onto Vulcan VX-72 at 13.2 MPa and 50 °C. The adsorbed metal precursor is converted to its metal form via three different routes: thermal conversion in N2 at ambient pressure (route 1), thermal conversion in scCO2 (route 2), or chemical conversion in H2 at ambient pressure (route 3). Sequential SCD is used in routes 1 and 3. The mean diameters of the synthesized Pt nanoparticles are smallest for route 1 and largest for route 3. Nano-scale morphology of the electrocatalysts is characterized using transmission electron microscopy (TEM), revealing narrower Pt particle size distributions for the catalyst prepared via route 1 than for those synthesized by routes 2 and 3. Electrocatalyst prepared using route 1 showed the best performance both in specific activity (measured via cyclic voltammetry) and in PEMFC tests among electrocatalysts prepared using different routes.

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