In a typical synthesis procedure, palladium (II) nitrate hexahydrate (Pd (NO3)2•2 H2O), Fe2(SO4)3, melamine, and citric acid (C6H8O7) were dissolved in anhydrous ethanol (50 mL) at different ratios. The mixture was then aged at 70 ºC for 4 h under stirring (300 rpm) until to obtain a green bubble gel, followed by drying at 100 ºC for 24 h in a drying oven to remove the excess solvent. The obtained green solid was then calcined at a fixed bed at 700 ºC for 3 h under a high-purity N2 (99.999 %) flow of 40 mL•min -1 . The heating rate was controlled at 2 ºC•min -1 . The obtained black solids were treated in 1 M H2SO4 aqueous solution at 70 ºC until the solution was colorless to remove the insecure and uncovered Pd particles. The black solids were then fully washed with deionized water until the pH of the waste solution was 7. Finally, the black solids were dried at -48 ºC for 12 h in a vacuum by using a freeze dryer. The dried black solids were denoted as Pd/Fe@N/C.