The morphology, microstructure, and electrochemical properties of platinum thin films deposited from aqueous ammonium hexachloroplatinate are dependent on the deposition potential. With increasing overpotential, the grain size increases and the films exhibit stronger (111) texture. Films deposited at low overpotential exhibit very small grain size and a preferred (311) texture. In addition, films deposited at -0.5 and -0.6 V are porous with very high surface areas. The electrochemical response of the films is dependent on the morphology and microstructure. (c) 2005 The Electrochemical Society.