Durable carbon-shell-encapsulated Pt/C catalysts synthesized by direct pyrolysis of Pt-pyrrole complexes for the oxygen reduction reaction

Owing to the robust protection of carbon layers, Pt catalysts sheltered by carbon layers (Pt@C/C) show superior durability towards the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFs). Herein, we report a convenient method for synthesizing the Pt@C/C catalyst by the thermal treatment of carbon-supported Pt-pyrrole complexes which have a specific mole ratio of Pt and pyrrole of -2.2. The obtained Pt nanoparticles (-3 nm) were well distributed and encapsulated by nitrogen-doped carbon layers. Notably, the pyrolyzing temperature has critical effects on the ORR activity of the Pt@C/C catalysts, with the Pt@C/C catalyst obtained at 700 degrees C (Pt@C/C700) exhibiting the best performance and far exceeding that of commercial Pt/C during potential cycling. TEM results show that the performance robustness of Pt@C/C700 is ascribed to the protection of ultra-thin carbon shells. In the cell test, the performance of the membrane-electrodeassembly with the Pt@C/C700 as the ORR catalyst was largely retained after the accelerated stress test, with a loss of only 12 mV at 0.8 A/cm2. The improved stability of Pt@C/C700 can result from the carbon shell's stabilizing effect which physically isolated the Pt nanoparticles from the harsh environment and prevented their degradation. This facile