The present invention relates to a complex having the advantages of economical efficiency, excellent catalyst activity, and significantly improved stability compared to conventional pure platinum catalysts, and specifically, the complex according to the present invention comprises: a carbon support; and a binary alloy supported on the carbon carrier and containing platinum (Pt) and an alkaline earth metal, in which E1 and E2 defined by formula 1 and formula 2 satisfy formula 3 in a Pt 4f XPS spectrum of the binary alloy as determined by X-ray photoelectron spectroscopy (XPS). (Formula 1) E1 = E0-E0 (ref) (Formula 2) E2 = EII-EII (ref) (Formula 3) E1/E2 is less than or equal to 0.85, in the Formula 1 and the Formula 2, E0 (ref) and EII (ref) are respectively the binding energy (center) of a Pt (0) peak and the binding energy (center) of a Pt (II) peak in a Pt 4f XPS energy spectrum of pure platinum (Pt), and E0 and EII are respectively the binding energy (center) of the Pt (0) peak and the binding energy (center) of the Pt (II) peak in the Pt 4f XPS energy spectrum of the binary alloy.
