Abstract
The sluggish oxygen reduction reaction (ORR) kinetics has inhibited the widespread commercialization of polymer electrolyte membrane fuel cells (PEMFCs). Therefore, there has been a great need for catalysts that promote the ORR. PtCo intermetallic nanoparticles supported on conductive carbon, which have superior activity and durability toward the ORR, have been considered promising catalysts for the cathode in PEMFCs. In general, high-temperature annealing is required to synthesize intermetallic catalysts, which accompanies the sintering of the nanoparticles, leading to a decrease in electrochemical active surface area (ECSA). Therefore, a sophisticated strategy is required to enhance the ordering degree of PtCo intermetallic compound nanoparticles without making the annealing process extreme. Here, we present L10-Zn-PtCo intermetallic nanocatalysts (Zn-PtCo/Zn-NC) in which the Zn incorporation strategy enhances the ordering degree. Computational calculation using machine learning force field (MLFF) elucidates that introducing Zn atoms can promote diffusion kinetics within the crystal structure of PtCo. X-ray diffraction (XRD) patterns and extended X-ray absorption fine structure (EXAFS) quantitatively confirm the enhancement of the ordering degree due to incorporating Zn atoms. In the half-cell configuration, the synthesized Zn-PtCo/Zn-NC catalyst shows an initial mass activity of 1.76 A mgPt -1 at 0.9 VRHE. In addition, it maintains 93.8% of its initial ECSA after the accelerated durability test (ADT). In H2-Air fuel cells, the Zn-PtCo/Zn-NC cathode achieves a high peak power density of 0.64 W cm-2, compared to that of the Pt/C (0.50 W cm-2), even with a low Pt usage of 0.05 mgPt cm-2 at the cathode.
Published Version
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