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

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.