An individually addressable array of nanostructured Pt microelectrodes was designed and prepared according to the concept of combinatorial electrochemistry. Different nanostructures on the array were obtained systematically by electrochemical deposition under cyclic voltammetric conditions. The surface structure and electrochemical behavior of the array were investigated, respectively using scanning tunneling microscopy (STM) and cyclic voltammetry (CV), and electrocatalytic properties of the array towards methanol oxidation were studied by CV and in situ microscope Fourier transform infrared reflection spectroscopy (MFTIRS). The results revealed the higher electrocatalytic activity of nanostructured Pt surfaces. and demonstrated that the combination of an individually addressable array with in situ MFTIRS is an efficient combinatorial approach in studies of electrocatalytic reaction processes at molecular level. (c) 2007 Published by Elsevier Ltd.