Influence of Cathode Catalyst Layer with SiO₂-Coated Pt/Ketjen Black Catalysts on Performance for Polymer Electrolyte Fuel Cells

Abstract

In this study, we investigated the effect of silica (SiO2) layer included in a cathode catalyst layer (CL) on the performance for polymer electrolyte fuel cells (PEFCs). Porous carbons such as Ketjen black (KB) have been widely used as a support for Pt catalysts in PEFCs. Such KB-supported Pt catalyst (Pt/KB) was used as a cathode CL with low ionomer content (a condition of low proton conductivity). The Pt/KB was then coated with SiO2. In addition, the Pt/KB and SiO2-coated Pt/KB (SiO2-Pt/KB) were measured and analyzed under relative humidity (RH) conditions (100% and 20%). The catalyst ink of SiO2-Pt/KB showed higher stability and dispersion compared to Pt/KB, due to the hydrophilic surface characteristics of SiO2, which act as a binder-like ionomer. The performance of the SiO2-Pt/KB at 100% RH, was significantly lower than that of Pt/KB, whereas the performance of the Pt/KB at 20% RH, was significantly improved by SiO2 coating. This is due to an increase in the proton conductivity, which can be attributed to the hydrophilic properties of SiO2. Based on these results, the effect of SiO2 coating on performance, depending on carbon supports of SiO2-coated Pt/Carbon catalysts, could be evaluated.

Keywords

• silica-coated Pt catalyst
• porous carbon
• catalyst layer
• silica coating
• polymer electrolyte fuel cell