A low-melting-point metal doping strategy for the synthesis of small-sized intermetallic Pt5Ce fuel cell catalysts

Carbon-supported platinum-lanthanum (Pt-Ln) intermetallic compound (IMC) nanoparticles with high activity and robust stability have been demonstrated as promising cathode catalysts for proton-exchange membrane fuel cells. However, the preparation of Pt-Ln IMC catalysts needs high-temperature annealing treatment that inevitably causes nanoparticle sintering, resulting in significant reduction of the electrochemical surface area and mass-based activity. Here, we prepare small-sized M-doped Pt5Ce (M = Ga, Cd, and Sb) IMCs catalysts via a low-melting-point metal doping strategy. We speculate that the doping of low-melting-point metals can facilitate the generation of vacancies in the crystal lattice through thermal activation and thus reduce the kinetic barriers for the formation of intermetallic Pt5Ce catalysts. The prepared Ga-doped Pt5Ce catalyst exhibits a higher electrochemical active surface area (81 m2·gPt−1) and a larger mass activity (0.45 A·mgPt−1 at 0.9 V) over the undoped Pt5Ce and commercial Pt/C catalysts. In the membrane electrode assembly test, the Ga-doped Pt5Ce cathode delivers a power density of 0.98 W·cm−2 at 0.67 V, along with a voltage loss of only 27 mV at 0.8 A·cm−2 at the end of accelerated stability test.