| Summary: | Minimizing the use of platinum (Pt) in catalysts for the oxygen reduction reaction (ORR) is critical for the commercial application of fuel cells. Here, we report a highly active carbon-supported catalyst with a low loading of Pt nanoparticles (Pt/C-N, 7.13 wt% Pt), prepared using a small molecular Pt complex containing Pt−N4 moieties as the Pt precursor. It was confirmed that Pt nanoparticles with an average diameter of <3 nm were uniformly adsorbed on a nitrogen (N)-doped carbon surface by carbothermal reduction of a composite composed of Pt(NH3)42+ ions and carbon via strong electrostatic attraction. More importantly, it is found that single atoms of platinum and pyridinic N active sites for the ORR are created during this process. The Pt/C-N catalyst shows very high ORR performance in acidic media, with a mass activity of 108 mA/mgPt−1 (at 0.9 V vs. RHE), which is three times greater than that of a commercial Pt/C catalyst (20 wt% Pt, 35 mA/mgPt−1). The high ORR activity of the Pt/C-N catalyst is ascribed to the synergistic catalytic effect of the Pt nanocrystals and the atomically dispersed active sites, which include single atoms of Pt and pyridinic N.
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