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.
Highlights
Polymer electrolyte fuel cells (PEFCs) have attracted much attention as efficient power sources for fuel cell vehicles (FCVs), due to advantages such as their high energy efficiency, a low operating temperature (20–100 ◦ C), no emission of CO, CO2, and NOx, as well as their simplicity [1]
The use of expensive Pt metals used as electrode catalysts, especially at the cathode, where a significant amount of Pt metal is wasted by slow kinetics of oxygen reduction reaction (ORR), is a major drawback of PEFCs
We investigated the influence of SiO2 -coated Pt catalysts on cell performance when Ketjen black, known as one of the porous carbons, was used as a support for cathode catalysts
Summary
Polymer electrolyte fuel cells (PEFCs) have attracted much attention as efficient power sources for fuel cell vehicles (FCVs), due to advantages such as their high energy efficiency, a low operating temperature (20–100 ◦ C), no emission of CO, CO2 , and NOx, as well as their simplicity [1]. The use of expensive Pt metals used as electrode catalysts, especially at the cathode, where a significant amount of Pt metal is wasted by slow kinetics of oxygen reduction reaction (ORR), is a major drawback of PEFCs. The cell performance and durability are not adequate for the further popularization of PEFCs. In an effort to reduce the usage of Pt, cathode catalysts, such as low-Pt and non-precious metal catalysts, have been developed as potential materials for replacing Pt, and have improved Pt utilization [2,3,4].
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