Promotion mechanism of PtCo intermetallic ordered alloys in oxygen reduction reaction and its application in fuel cells

[Display omitted] •A surface Pt-rich PtCo ordered alloy with 3 nm size was successfully synthesized.•The PtCo catalyst exhibited impressive performance of 1.4 W cm−2 @ 0.6 V in H2-air fuel cell.•The key intermediate of adsorbed O2* was detected by in-situ ATR-FTIR spectroscopy.•The adsorption intenty of O2* on the ordered PtCo intermetallic alloy is between Pt and disordered PtCo. Ordered intermetallic Pt-M alloys are promising as next-generation low-Pt catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) due to the high ORR activity and excellent long-term stability. However, the mechanism behind the enhancement of ORR activity by ordering mostly comes from theoretical calculations, and experimental evidence is very lacking. Herein, we prepared a surface Pt-rich PtCo ordered alloy of about 3 nm in size, which exhibited high ORR catalytic activity, achieving impressive performance of 1.4 W cm−2 @ 0.6 V in H2-air fuel cell and mass activity of 0.62 A mgPt-1 @ 0.9 ViR-free in H2-O2 fuel cell. The key ORR intermediate, adsorbed *O2, was successfully detected by electrochemical in situ infrared spectroscopy. Compared with Pt and disordered PtCo, the ordered PtCo alloy has optimal adsorption interaction with *O2, accelerating the ORR kinetics.