Nanoengineered Ultra‐Thin Ultra‐Low PtZn@Ptskin Nanotubular Array Cathode with Improved Polarizations

Ordered cathodes of proton exchange membrane fuel cells (PEMFCs) suffer the lack of triple‐phase boundaries (TPBs) and polarization loss. We report the fabrication of PtZn@Pt skin porous nanotubular array (PNA) with infiltrated polytetrafluoroethylene (PTFE) to nanoengineer TPBs suitable for efficient O 2 transfer, proton conduction, electron conduction, as well as water drainage. The PTFE‐PtZn@Pt skin PNA is 290 ± 50 nm thick at 62.0 ± 1.0 µg Pt cm −2 and 3.9 ± 1.0 µg Zn cm −2 . The PNA exhibits 12.7%, 32.8%, and 82.1% of improved Ohmic, activation, and O 2 transfer polarizations relative to regular Pt/C cathode at 1 A cm −2 , respectively. For Ohmic polarization, the PNA falls within Debye length, where a strong electric field allows fast proton conduction with the aid of shortened and straightforward pathway along the PNA. For activation polarization, density functional theory (DFT) indicates that the d‐band center of PtZn@Pt skin downshifts and weakens O* adsorption relative to Pt, thus boosting the activity of oxygen reduction reaction (ORR). For O 2 transfer polarization, molecular dynamics (MD) simulations indicate that PTFE weakens hydrogen bond network and van der Waals force and mitigates water residence time at the interface of PTFE‐PtZn@Pt skin /water, leading to 9‐fold increase in local O 2 concentration.