Oxygen Reduction Reaction on Pt Nanoparticles Confined within a Hexaaminetriphenylene-Based MOF at the Electrode/Electrolyte and Electrode/Triple-Phase Boundary Interfaces

Herein, we report the results of evaluation of an oxygen reduction reaction (ORR) electrocatalyst comprising ca. 2 nm Pt nanoparticles, confined within a highly porous, amorphous carbon–nitrogen matrix, both at the electrode/electrolyte and electrode/triple-phase boundary interfaces. The catalyst was synthesized by a pyrolytic reduction of Pt(acac)2 nodes in the Pt(acac)2-hexaaminetriphenylene (Pt-HATP) cocrystal at 600 °C for 1 h. The pyrolyzed Pt-HATP electrocatalyst, with a Pt loading of 35 wt %, exhibits the electrochemical surface area (ECSA) of 38.8 ± 4.0 m2 gPt–1 and the area-specific activity of 150 μA cmPt–2 in thin-film rotating-disk electrode (RDE) experiments, which do not exceed those of commercial 40 wt % Pt/VC. Importantly, it demonstrates superior durability in RDE testing, attributed to lower losses in the ECSA due to suppression of nanoparticle coalescence/agglomeration during potential cycling. Evaluation of Pt-HATP in a membrane-electrode assembly (MEA) fuel-cell configuration shows a higher iR-corrected performance compared to the commercial catalyst. Although the Pt-HATP MEA exhibits significant high-frequency and proton resistances, it benefits from the lower Faradaic resistance manifested by a lower Tafel slope of 86 ± 10 vs 136 ± 10 mV for 40 wt % Pt/VC.