Hollow PtCu octahedral nanoalloys: Efficient bifunctional electrocatalysts towards oxygen reduction reaction and methanol oxidation reaction by regulating near-surface composition.

In response to the scarcity of precious metals, the development of precious-metal-saving electrocatalysts exhibiting high mass activity (MA) and durability towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) for both proton-exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) has aroused increasing attention. In this study, octahedral Cu-rich PtCu alloy is seeded to fabricate near-surface composition-tunable PtCu hollow octahedral nanoparticles (HONs) with the wall thickness of ~2.1 nm. Due to both the alloying effects of near surface and the special hollow octahedral structure, the PtCu/C HONs exhibit significantly higher MA and durability than commercial Pt/C towards both ORR in alkaline medium and MOR in sulfuric acid electrolyte. The ORR MA of Pt44.1Cu55.9/C HONs are up to 2.60 A mgPt-1 that is 18.5-fold enhancement compared with that of Pt/C. Besides, after 10,000 voltage cycles, the MA of Pt44.1Cu55.9/C HONs remains to be 1.61 A mgPt-1, a datum 53.7 times that of Pt/C. The in situ CO polarization curves exhibit that the Pt44.1Cu55.9 HONs/C own high resistance to CO poisoning. For MOR in sulfuric acid electrolyte, the optimum SA/MA of PtCu/C HONs is 5.33 mA cm-2/1.94 A mgPt-1, which is 10.25/5.87 times higher than that of Pt/C. This study provides effective bifunctional cathode and anode electrocatalysts for both PEMFCs and DMFCs.