Single step polyol synthesis of highly stable Pt/C/SiO₂ catalysts for use in PEMFCs: effects of pH, temperature and W/EG ratio

LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy Faculty of Engineering of the University of Porto, Rua Dr. Roberto Frias, 4200–465 Porto, Portugal

^* Corresponding author: mendes@fe.up.pt

Abstract

Hybrid supports have been proposed as a new alternative to increase the stability of ORR catalysts used in PEMFCs for automotive applications since they are known to be stable under harsh conditions. In this work, Pt nanoparticles were deposited over C/SiO2, via single-step polyol method, to take advantage of the corrosion-resistance properties of silica nanoparticles. In fact, the synthesis parameters, namely, pH, temperature, and glycol concentration had a remarkable impact on the Pt size-distribution, crystallinity, and dispersion over the C/SiO₂ supports. A maximum ORR activity and stability was obtained for Pt/C/SiO₂ catalysts produced at 1:6 W/EG (v/v). The addition of SiO₂ nanoparticles to the carbon structure showed their ability to effectively inhibit support corrosion and Pt nanoparticles detachment and/or growth, with the pH adjustments being critical for obtaining highly stable C/SiO₂ supports. Pt/C/SiO₂ synthetized under acidic conditions revealed the highest stability when subjected to accelerated stress tests (ASTs), losing only 30 % of the initial electrochemically active surface area (ECSA) of Pt after 4 000 cycles from 0.6 to 1 V (vs RHE), whereas the commercial Pt/C revealed > 50 % of ECSA loss.