Date Published: March 13, 2019
Publisher: John Wiley and Sons Inc.
Author(s): Yi Cheng, Shuai He, Shanfu Lu, Jean‐Pierre Veder, Bernt Johannessen, Lars Thomsen, Martin Saunders, Thomas Becker, Roland De Marco, Qingfeng Li, Shi‐ze Yang, San Ping Jiang.
Iron single atom catalysts (Fe SACs) are the best‐known nonprecious metal (NPM) catalysts for the oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cells (PEMFCs), but their practical application has been constrained by the low Fe SACs loading (<2 wt%). Here, a one‐pot pyrolysis method is reported for the synthesis of iron single atoms on graphene (FeSA‐G) with a high Fe SAC loading of ≈7.7 ± 1.3 wt%. The as‐synthesized FeSA‐G shows an onset potential of 0.950 V and a half‐wave potential of 0.804 V in acid electrolyte for the ORR, similar to that of Pt/C catalysts but with a much higher stability and higher phosphate anion tolerance. High temperature SiO2 nanoparticle‐doped phosphoric acid/polybenzimidazole (PA/PBI/SiO2) composite membrane cells utilizing a FeSA‐G cathode with Fe SAC loading of 0.3 mg cm−2 delivers a peak power density of 325 mW cm−2 at 230 °C, better than 313 mW cm−2 obtained on the cell with a Pt/C cathode at a Pt loading of 1 mg cm−2. The cell with FeSA‐G cathode exhibits superior stability at 230 °C, as compared to that with Pt/C cathode. Our results provide a new approach to developing practical NPM catalysts to replace Pt‐based catalysts for fuel cells.
Materials Synthesis and Cell Fabrication: Hemin porcine (HP, C34H32ClFeN4O4, Sigma‐Aldrich) and dicyandiamide (C2H8N2, Sigma Aldrich) were purchased and used without further treatment. HP (100 mg) was mixed with C2H8N2 (10 g) with the addition of 20 mL ethanol, and the mixture was ground until dry. This process was repeated four times. Subsequently, the mixture was heated at 350 °C for 3 h and then at 650 °C for 3 h before being heated at 900 °C for 1 h under Ar at a flow rate of 50 mL min−1. Cells with an active area of 4 cm2 were fabricated by sandwiching SiO2/PA/PBI membrane between two gas diffusion electrodes consisting of a Pt/C anode and FeSA‐G cathode (Figure S2, Supporting Information).30
The authors declare no conflict of interest.