A sub-4 nm PtCu₃ intermetallic catalyst with an L1₂-ordered structure toward efficient activity and durability for oxygen reduction

Pt-based intermetallic alloys have shown bright prospects for promoting the activity and durability of fuel cell cathode oxygen reduction. However, avoiding particle sintering in the preparation of highly ordered platinum-based intermetallic compounds remains a challenge. In this work, urea was introduced for high-temperature co-reduction to obtain highly ordered intermetallic nanocrystals of ultra-small size (<4 nm) with an L1(2) phase structure. The attained L1(2)-PtCu3/C achieves a half-wave potential of 0.941 V and possesses a mass activity of 1.33 A mg(Pt)(-1) reaching 11.1 times that of commercial Pt/C. After a 20k accelerated durability test, L1(2)-PtCu3/C shows higher stability with a slight drop of half-wave potential by only 13 mV, and the mass activity decreased by only 27.1%. Density-functional theory indicates that the doping of transition metal Cu atoms and the formation of ordered intermetallic structures can introduce compressive strains that lower the d-band centers, weakening the adsorption of oxygen-containing intermediates and thus enhancing the catalytic activity.