Catalytic Activity of Highly Durable Pt/CNT Catalysts Covered with Hydrophobic Silica Layers for the Oxygen Reduction Reaction in PEFCs

Abstract

Carbon nanotube-supported Pt catalysts (Pt/CNT) for the cathode in a polymer electrolyte fuel cell (PEFC) were covered with silica layers using tetraethoxysilane (TEOS) and also methyltriethoxysilane (MTEOS) to improve the catalyst durability under the severe conditions at the PEFC cathode. Both the silica-coated Pt/CNT catalysts had excellent durability for potential cycling between 0.6 and 1.0 V (vs RHE) in N 2 -purged 0.1 M HClO 4 electrolyte, while Pt/CNT without silica coating was significantly deactivated due to an increase of the Pt metal particle size. Silica-coated Pt/CNT prepared from MTEOS had similar activity for the oxygen reduction reaction as Pt/CNT without silica coating, whereas the silica coverage obtained with TEOS slightly reduced the catalytic activity of the Pt/CNT catalyst. The silica layers prepared from MTEOS are more hydrophobic than those prepared from TEOS due to the presence of methyl groups. In addition, the silica layers prepared from MTEOS have larger pores than those prepared from TEOS. The hydrophobic silica layers with larger pores in the silica-coated Pt/CNT do not inhibit the diffusion of the reactants (oxygen) and the discharge of the products (water) during the oxygen reduction reaction.

Recent advancements in Pt and Pt-free catalysts for oxygen reduction reaction

“…[230][231][232][233][234][235][236][237][238][239] For example, as for metal clusters, modifying Pt nanoparticles with Au clusters has been already proved to be efficient in stabilizing Pt against dissolution under harsh fuel cell work environment, as demonstrated by Zhang et al 230 More importantly, there were no leakage issues on Au. [230][231][232][233][234][235][236][237][238][239] For example, as for metal clusters, modifying Pt nanoparticles with Au clusters has been already proved to be efficient in stabilizing Pt against dissolution under harsh fuel cell work environment, as demonstrated by Zhang et al 230 More importantly, there were no leakage issues on Au.…”

Highly uniform distribution of Pt nanoparticles on N-doped hollow carbon spheres with enhanced durability for oxygen reduction reaction

“…have been chosen as substitutes of carbon black to gain an extended lifetime of PEMFCs. [21][22][23][24] HCSs as one kind of novel carbon materials have long been appealing in various energy storage and conversion devices, biomedicine and environmental treatment due to their unique structures with low density, high surface to volume ratio and high mechanical strength. [25][26][27][28] HCSs could effectively improve the dispersion of Pt-based electrolytes and stabilize Pt NPs from dissolution and aggregation via steric effect generated from pore connement or encapsulation.…”

Highly durable platelet carbon nanofiber-supported platinum catalysts for the oxygen reduction reaction

“…For the ECSA measurements, the applied potential was swept from 1.0 to 0.3 V vs. RHE with a potential-sweep rate of 50 mV s À1 in the argon-saturated electrolyte. The ECSA measurement was performed by integrating the charges associated with the hydrogen-adsorption/desorption region and by assuming a value of 210 lC cm À2 for the desorption of monolayer H ads on Pt [24][25][26]. Each ECSA value is normalized to the original active surface area.…”