Tuning the surface structure and phase structure of PtCu3 nanoparticle for highly efficient electrocatalysts

Significantly improving the catalytic activity and durability of platinum (Pt) based electrocatalysts is crucial for commercial application of fuel cells by tuning structure of Pt alloy nanoparticles. Here, we report a method of tuning structure of PtCu 3 alloy nanoparticle by annealing in different atmospheres. The detailed analyses showed that evolution of surface structure and phase structure of PtCu 3 alloy nanoparticles heat-treated in N 2 atmosphere and N 2 /H 2 mixed atmosphere are mainly as follows: (1) when heat-treated in N 2 , the crystal phase of PtCu 3 has undergone a transformation from disordered PtCu 3 alloy to ordered PtCu 3 alloy and then to disordered PtCu 3 alloy with the increase of holding time from 30 min to 90 min; (2) when heat-treated in H 2 /N 2 , a Pt-rich surface is formed on the Pt–Cu nanoparticles due to Pt segregation induced by H 2 adsorption. Electrochemical measurements demonstrated that both PtCu 3 /C -N2 electrocatalysts prepared in N 2 and PtCu 3 /C -N2/H2 electrocatalysts prepared in H 2 /N 2 exhibit enhanced mass activities toward the oxygen reduction reaction (ORR) relative to Pt/C electrocatalyst in acidic media. In particular, when the holding time is 90 min, the obtained PtCu 3 /C -N2/H2 electrocatalysts with Pt-rich surface showed highest mass activity of 435 mA/mg Pt (at 0.9 V vs. RHE), which is four times greater than that of Pt/C catalyst (20 wt.% Pt, 115 mA/mg Pt ). This study provides a promising method for the reasonable design and preparation of low cost and high performance Pt-based electrocatalysts. • Surface and phase structure of PtCu 3 nanoparticle are tuned by annealing in different atmospheres. • Crystal phase of PtCu 3 heat-treated in N 2 gas has undergone a transformation from disorder to order. • Formation of Pt-rich surface on Pt–Cu nanoparticles due to Pt segregation induced by H 2 adsorption. • The PtCu 3 /C catalyst with Pt-rich surface exhibits a higher ORR activity compared to Pt/C catalyst.