Hydrogen evolution reaction (HER) was studied in alkaline solution on Pt(poly) electrode modified by spontaneously deposited Ir nanoislands. Comprehensive insight into the characteristics of the bimetallic Ir/Pt(poly) catalysts was obtained by a combination of Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS) and classical electrochemical techniques. HER investigations have shown that the presence of spontaneously deposited Ir enhances the activity of bare Pt(poly) in alkaline solution. This was attributed to the heterogeneity of the active surface sites and to the electronic interaction between two metals in close contact which together facilitated the adsorption of the H intermediate species. (c) 2019 Elsevier Ltd. All rights reserved.