Porphyrinic Carbon Electrocatalysts Decorated with Ultralow Active Metal for Oxygen Reduction Reaction (ORR)

The high cost combined with limited performance and low durability of precious metal based-catalysts are major technical barriers to overcome for the commercialization of polymer electrolyte fuel cells (PEFCs). Therefore, exploring the cost effective electrocatalyst with enhanced activity focuses on (1) Pt-M alloy/dealloy with inexpensive transition metals and (2) non-precious metal based electrocatalysts. Unfortunately, the performance of non-precious metal-based materials is still inferior to that of Pt-based catalysts in respect of cell activity and lifespan. Recently, although we found that the self-supported ordered mesoporous porphyrinic carbon (M-OMPC) doped with transition metals, which revealed to have a comparable catalytic activity with Pt/C towards oxygen reduction reaction (ORR), a relatively large amount of catalyst (> 0.6 mg/cm²) is required to be loaded. The catalytic behavior of M-OMPC for ORR is depended on the morphology and mass of the catalyst on the electrode. Thus, a thick membrane electrode with a high catalyst loading is unfavorable for the cell performance in terms of cell resistance and conductivity. In this study we demonstrated an alternative catalyst combined with M-OMPC as a substitution for carbon supports generally used and a trace of Pt particles. The ultralow Pt (<5 wt%) loading on M-OMPC (Pt/M-OMPC) showed a 10-fold enhancement of ORR kinetic activity compared to that of M-OMPC at 0.9 V RHE. The Pt mass activity was also improved by two times compared to that of Pt/C at 0.85 V RHE.