Platinum electrocatalysts attached to carbon nanotubes by atomic layer deposition with different cycle numbers

• This study adopts atomic layer deposition (ALD) to prepare ultra-low Pt loading.
• The ALD cycle number serves as a key factor in controlling the Pt loading.
• The average particle size of Pt nanoparticles shows an increase with the ALD cycle.
• The catalyst electrode generates superior peak power density of 7.8 kW/g at 75 °C.

This study adopts an atomic layer deposition (ALD) process to prepare ultra-low Pt loading over the surface of carbon nanotubes (CNTs), showing superior power density in single-stack proton exchange membrane fuel cells (PEMFCs). The ALD cycle number (i.e., 50, 100, 200, and 400 cycles) serves as a key factor in controlling the particle size and the weight loading of Pt deposits. Two linear plots of the Pt loading and the particle size versus the ALD cycle number confirm the presence of self-limiting reaction steps. The growth rate is estimated to be 0.0013 mg/cm2/cycle. The average particle size of Pt nanoparticles shows an increase with the ALD cycle, i.e., 2.49–25.5 nm within 50–400 ALD cycles. The gas diffusion electrode (GDE) equipped with as-grown Pt catalysts, prepared from ALD 50 cycles, generates superior peak power density of 7.8 kW/g at 75 °C, showing a novel design of GDE for PEMFCs.