High-performance proton exchange membrane fuel cell with ultra-low loading Pt on vertically aligned carbon nanotubes as integrated catalyst layer

Abstract

Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells (PEMFCs). To achieve this goal, constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role. Herein, PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by E-beam onto vertically aligned carbon nanotubes (VACNTs) growth on Al foil via plasma-enhanced chemical vapor deposition. Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance, in particular at high current densities. When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6 μm, the cell shows the highest performance, compared with others with various lengths of VACNTs. It delivers a maximum power output of 1.61 W cm−2 (H2/O2, 150 kPa) and 0.79 W cm−2 (H2/Air, 150 kPa) at Pt loading of 50 μg cm−2, exceeding most of previously reported PEMFCs with Pt loading of < 100 μg cm−2. Even though the Pt loading is down to 30 μg cm−2 (1.36 W cm−2), the performance is also better than 100 μg cm−2 (1.24 W cm−2) of commercial Pt/C, and presents better stability. This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities. This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes, demonstrating the most possibility to achieve a substantial reduction in Pt loading <100 μg cm−2 without sacrificing in performance.