A Pd-doped Pt3Sn-based single atom alloy catalyst (Pd-Pt3Sn) was synthesized via a hydrothermal method. The overpotential of Pd-Pt3Sn is lower than that of commercial Pd/C and IrO2 catalysts at 10 mA cm-2. This is due to the synergistic effect between Pt, Sn and Pd and the influence of electronic effects on their catalytic performance.