<p>Suspended solids of AgCl are formed in aqueous solutions containing both K₂PtCl₄ and AgNO₃. When Ni wire is immersed in an aqueous solution containing 1.0&#xa0;mM K₂PtCl₄ and 1.0&#xa0;mM AgNO₃, it was found that platinum nanoparticles (PtNPs) were deposited on Ni wire after the immersion of 10&#xa0;min. This was confirmed by observing the electrocatalytic responses for ethanol oxidation as well as the FE-SEM images with EDS analysis. While the deposition of PtNPs is generally unfavorable on the surface of Ni wire by immersing it in an aqueous solution containing only K₂PtCl₄, it was clarified that the coexistence of PtCl₄²⁻ (or other chemical species that contain Pt²⁺) with AgCl (and Ag⁺) promoted the galvanic replacement reactions with Ni to deposit PtNPs. The electrocatalytic responses for ethanol oxidation significantly changed depending on [K₂PtCl₄] and [AgNO₃] in aqueous solutions for the preparation; AgNPs were dominantly deposited in some conditions. Compared with PtNPs modified Ni (PtNPs/Ni) wire electrodes prepared using other methods, the electrocatalytic current recorded with the present PtNPs/Ni wire electrodes were increased over 50 mAcm⁻².</p> Graphical abstract <p></p>