Study on the Triple‐Phase Boundary Structure in Porous Electrode via the CO Pulse‐Titration Method

The triple‐phase boundary (TPB) significantly influences the performance and durability of Pt/C electrodes in fuel cells, water electrolyzers, and electrochemical devices. However, a comprehensive understanding of the meso‐ and microstructures of the TPB is still lacking. Herein, a CO pulse‐titration method to investigate the TPB, especially the ionomer coverage in the Nafion/Pt interface region, is proposed. By leveraging the specific CO absorption properties on the Pt/C electrocatalyst, the surface area of commercial 60 wt% Pt/C could be calculated as 80.00 m 2 g Pt −1 , validating the effectiveness of this method. Moreover, the ionomer coverage of the Nafion/Pt interface region increases with the growing ionomer/carbon mass ratios, while variations in Nafion coverage are observed in porous electrodes with the same ratios due to the differences in fabrication processes for porous electrodes. These findings could offer new insights into the interfacial structures of porous electrodes.