Characterization of electrocatalytic proton reduction and surface adsorption of platinum nanoparticles supported by a polymeric stabilizer on an ITO electrode

Abstract

Platinum nanoparticles stabilized by a polymeric stabilizer of polyacrylic acid (PAA-Pt) were adsorbed on an indium tin oxide (ITO) surface from their colloidal solution due to the chemical adsorption between PAA and the ITO surface to afford a transparent PAA-Pt nanoparticle-coated electrode. The adsorption of PAA-Pt nanoparticles and their electrocatalytic proton reduction were investigated compared with the case of citrate-stabilized Pt nanoparticles (citrate-Pt). The adsorption of PAA-Pt nanoparticles is faster than that of citrate-Pt nanoparticles, ascribed to the concerted adsorption of PAA-Pt nanoparticles by the polymeric chain effect of PAA. The thermodynamic parameters for adsorption are close between citrate-Pt and PAA-Pt nanoparticles. The citrate-Pt and PAA-Pt nanoparticle-coated electrodes worked efficiently for electrocatalytic proton reduction. Although the mass activity (0.18 mA cm⁻² nmol⁻¹) of PAA-Pt/ITO for proton reduction at −1.0 V vs. Ag/AgCl was 1.4 times lower than that (0.26 mA cm⁻² nmol⁻¹) of citrate-Pt/ITO, the catalytic current for the PAA-Pt/ITO was significantly stable due to the PAA stabilizer.