Pt electrodeposition on a copper surface modified with 3-mercaptopropyltrimethoxysilane and 1-propanethiol

Abstract

Platinum nanoparticle growth by electrochemical deposition on a copper surface modified with mercaptopropyltrimethoxysilane (MPS) and 1-propanethiol (1-PT) was studied by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The electrodeposition of Pt was done using an aqueous solution of pH 3.9, because under these conditions, MPS and 1-PT molecules remain on the copper surface. The Pt(IV) reduction peak on a clean copper surface was observed near −600 mV vs. SCE and the oxidation peak near −450 mV (vs. SCE). The hydrogen desorption peak was observed near −850 mV. The lower value of the pinhole radii ( R a) was 1.0×10 −6 cm (10 nm) for the Cu/1-PT system. This result is in agreement with the effective ionic radius of the Pt(IV) (0.63 Å) so that Pt can enter the pinhole and be reduced on the copper surface. The diffusion coefficient ( D) of Pt(IV) was 1.3×10 −9 cm 2 s −1. The amounts of MPS and 1-PT molecules on the copper surface play an important role in obtaining platinum nanoparticles, because they have a controlling effect on the size of the nanoparticles deposited. The Pt particle diameters on Cu/MPS and Cu/1-PT surfaces were 13 and 9 nm, respectively. This demonstrates that 1-PT exerts better control of the platinum particle size on the copper surface than MPS.