Improved thermal stability, properties, and electrocatalytic activity of sol-gel silica modified carbon supported Pt catalysts

An improvement in the thermal properties of catalysts used in PEM type fuel cells was achieved by siliceous additions. A sol-gel method was developed to deposit controlled amounts of a siliceous composition on Vulcan XC72 carbon (VC). The catalysts designated as Pt/(VC–SiO2) were obtained by reduction of H2PtCl6 in an aqueous solution with NaBH4. A nanoscale Pt particle formation was observed on the support materials having a range 2.7–5.1 nm. The thermal stability study for Pt/(VC–SiO2) catalysts demonstrated that the presence of a siliceous phase conferred an increased resistance to Pt nanoparticle agglomeration at 600 °C. In addition, a decrease in low temperature mass loss was observed. Electrochemical properties evaluated by cyclic voltammetry coupled with a rotating disk electrode (RDE) showed improvements with moderate SiO2 addition. The synthesized catalysts performance was as good as the performance of the control catalyst (46 wt% Pt/VC, Tanaka). Unfortunately, fuel cell performance experiments showed an unwanted hydrophillic behavior of carbon-silica composite aerogel supports at high current density values. The C–SiO2 aerogel composite catalyst support seems suitable for low current applications.

► C–Aerogel SiOx composite catalyst support material was synthesized, characterized and evaluated in fuel cell conditions.
► Homogeneously distributed 2–5 nm sized Platinum particles were obtained with the SiOx modified support materials.
► Improved fuel cell performance results were obtained with SiOx modified catalysts.
► Improved thermal stability was obtained with SiOx modified catalysts.
► SiOx addition was optimized for improved performance.