High-performance alcohol electrooxidation on Pt3Sn–SnO2 nanocatalysts synthesized through the transformation of Pt–Sn nanoparticles

Abstract

In this work, Pt₃Sn–SnO₂ supported on N-doped graphene (Pt₃Sn–SnO₂/NG) was synthesized through the in situ transformation of Pt–Sn/NG by annealing in an air atmosphere. The Pt₃Sn–SnO₂/NG catalyst, characterized by XRD, TEM and HRTEM, forms an ordered Pt₃Sn intermetallic in which every Pt₃Sn nanoparticle (NP) is in close contact with one or more SnO₂ NPs. The Pt₃Sn–SnO₂/NG catalyst shows outstanding performance towards the ethanol oxidation reaction (EOR) and methanol oxidation reaction (MOR). The mass activity for EOR on the Pt₃Sn–SnO₂/NG catalyst is 469 mA mg_Pt⁻¹ at 0.7 V, which is more than 10 times that of the commercial Pt/C catalyst (44 mA mg_Pt⁻¹). The Pt₃Sn–SnO₂/NG catalyst is found to have more than three times the stability of the commercial Pt/C. Our Pt₃Sn–SnO₂/NG catalyst also delivers increased activity and higher stability for MOR compared with the Pt/C catalyst. In addition, the Pt₃Sn–SnO₂/NG catalyst is observed to have a higher CO tolerance compared with Pt/C. The high activity and stability of the Pt₃Sn–SnO₂/NG catalyst can be attributed to the unique structure of Pt₃Sn–SnO₂, formed by the in situ transformation of Pt–Sn/NG, which induces the formation of a small-sized ordered Pt₃Sn intermetallic that strongly interacts with SnO₂. The synergetic effect between the ordered Pt₃Sn and SnO₂ enhances the activity towards EOR and MOR through the Sn in both Pt₃Sn and SnO₂, which facilitates the removal of CO_ads on the adjacent Pt active sites at low potentials by providing OH_ads species; it also improves stability because of the strong Pt₃Sn–SnO₂ interactions.