A Pt/Rh(100) bimetallic surface was prepared by electrochemical deposition of Pt ions on Rh(100). Annealing of the Pt/Rh(100) in O-2 led to chemical restructuring, and the LEED pattern changed from p(1 x 1) to a very sharp p(3 x 1) pattern. The cyclic voltammogram was measured for a clean Rh(100), a Pt-deposited Rh(100) and the reconstructed p(3 x 1) surface. The voltammogram was very sensitive to the topmost layer of the electrode, and the reconstructed p(3 x 1) surface showed a very similar voltammogram to Rh(100) surface. This proves the formation of a hybrid surface of Rh-O/Pt/Rh(100) which we proposed previously.