Synergy of Pt-Free Single Metal Sites for Promoting Pt and Pt3co Ordered Intermetallic Catalysts for Fuel Cells: Performance and Durability Improvements

The reduction of platinum use and improvement of its catalytic performance has become the most critical steps to accelerate the development of proton-exchange membrane fuel cells (PEMFCs). Here we report a novel and facile method to boost the performance of the Pt-cased catalyst by integrating with an atomic platinum-group metal (PGM)–free active sites. Using iron-doped zeolitic imidazolate framework-8 (ZIF-8) derived carbon as support, we achieved a uniform deposition of Pt and intermetallic Pt-Co nanoparticles (NPs) through one-step synthesis, with average particle size 2.4 nm for Pt, 3.4 nm for L1 0 PtCo, and 4.2 nm for L1 2 Pt 3 Co. Besides, easy phase transfer during synthesis between ordered intermetallic structures L1 0 PtCo and L1 2 Pt 3 Co was achieved, and a comprehensive comparison between their catalytic performance was established. Synergistic catalysis between Pt or Pt-Co NPs over a PGM–free catalytic substrate derived from iron-doped ZIF-8 led to excellent oxygen reduction reaction (ORR) performance under both rotating disk electrode (RDE) and membrane electrode assembly (MEA) testing. Resulting pure Pt catalysts achieved ORR mass activities of 0.451 A/mg Pt and retained 80% initial values after 30,000 voltage cycles in a fuel cell, superior to the DOE 2020 targets without using Pt alloy. Both PtCo and Pt 3 Co catalysts achieved better performance and exhibited all-sided excellence among mass activity, stability, and power density. Among them, Pt 3 Co reached the power density at 0.67 V of 923 mW/cm 2 and retained 86% initial mass activity after 30,000 voltage cycles in a fuel cell. Their performance dependences on support material particle size and ionomer content were discussed and optimized in MEAs.