Engineering Triple‐Phase Boundary in Pt Catalyst Layers for Proton Exchange Membrane Fuel Cells

Engineering triple‐phase boundaries in low Pt‐loaded catalyst layers is highly desired yet challenging due to the poor Pt utilization caused by inhomogeneous Nafion ionomer coverage over catalyst nanoparticles and high mass transport resistance near catalyst surface. Herein, an effective Pt catalyst/support design strategy by using urea to modify the carbon supports is reported, in which the balance between nitrogen doping and Pt nanoparticle deposition can be well achieved without sacrificing catalyst performance. The nitrogen‐modified carbon with the positively charged surface can electrostatically attract with ionomer with negative charges in a catalyst ink. Meanwhile, ionomer can be preserved into a solid catalyst layer, forming a desirable ionomer/catalyst interface with improved dry proton accessibility and lowered oxygen transport resistance. Consequently, this interface leads to striking performance improvement in the kinetic and mass transport regions in the membrane electrode assembly level, with the current density of 1.11 A cm−2 at 0.65 V under 50% RH and 85 °C operating conditions, reaching 2.8 times this value compared with the one without modification. The nitrogen‐doped carbon with a positively charged surface can attract negatively charged Nafion ionomer via Coulombic interaction, allowing the realization of building an active triple‐phase boundary at the Pt catalyst layer. With this ideal catalyst layer, better management of oxygen, electrons, and protons occurring on the triple‐phase boundary gives rise to enhanced catalytic performance for proton exchange membrane fuel cells.