Ordered Nanostructural Engineering of Cathode Catalyst Layer With High Mass Transport Efficiency for High‐Performance Ultra‐Low Pt Loading Proton Exchange Membrane Fuel Cells

The order‐structured cathode catalyst layer (CCL) has been considered the most promising solution to construct low‐cost proton exchange membrane fuel cells (PEMFCs) with an ultra‐low Pt loading (<100.0 μg cm −2 ). Herein, the ordered CCL was developed by depositing Pt nanoparticles onto the vertically aligned carbon nanotube film (Pt/VACNTs) via atomic layer deposition. Compared to the disordered CCL prepared by random Pt/CNTs obtained by dispersing Pt/VACNTs, the Pt/VACNTs‐ordered CCL is characterized by higher porosity (41.64%) and smaller tortuosity (1.29), leading to a 54% and 53% reduction of oxygen transport resistance and proton transport resistance, respectively. As a result, the cell with Pt/VACNTs‐ordered CCL at a Pt loading of 80.0 μg cm −2 produces the maximum power density of 1.01 W cm −2 (H 2 /Air, 150.0 kPa), much higher than the cell with the same Pt loading Pt/CNTs‐disordered CCL (0.69 W cm −2 at 80.0 μg cm −2 ) and commercial Pt/C CCL (0.77 W cm −2 at 200.0 μg Pt cm −2 ). Meanwhile, the Pt/VACNTs‐ordered CCL also exhibits a higher durability with only a power density loss of 19.4% and a voltage loss of 29.7 mV at 0.8 A cm −2 after 30 000 cycles of accelerated stress test, compared with that of Pt/C (a power density loss of 33.2% and a voltage loss of 80.0 mV). This work further identifies the critical role of ordered CCLs in charge and mass transport for developing ultra‐low Pt loading PEMFCs.