Pd-Sn alloy nanoparticles for electrocatalytic methanol oxidation: Phase evolution from solid solution to intermetallic compounds

Developing efficient catalysts with high activity and durability via alloying strategy is essential to the energy conversion in various electro-catalytic reactions. Among the different alloy structures, intermetallic compounds (IMCs) have received much attention recently due to the special geometric and electronic effects and outstanding activity and durability, endowed by their ordered structure. Herein, A series of hollow-structured nanocrystals of Pd-Sn alloy, including face-centered cubic solid solution of Pd(Sn), IMCs of Pd₂Sn, and IMCs of Pd₃Sn₂, are fabricated via a solvothermal strategy by varying the precursor ratio of Pd and Sn. The structure difference of the nanocrystals has been investigated via combined electron microscopy and spectroscopy, assisted by local elemental separation analysis and X-ray spectroscopy. Among all, Pd₃Sn₂ IMCs show outstanding methanol oxidation reaction (MOR) activity in terms of mass activity (1.3 A·mg_Pd⁻¹) and specific activity (5.03 mA·cm⁻²). Through density functional theory (DFT) simulation calculations on three different Pd-Sn alloy models, the performance has been well understood. As compared with Pd(Sn) and Pd₂Sn, the high MOR kinetics on Pd₃Sn₂ is featured by its weaker CO adsorption and favorable CO–OH co-adsorption.