Enhanced cell performance: Incorporation of hydrophobic mesoporous silica into the triple-phase boundary of catalyst layer

The advantages of high-temperature proton exchange membrane fuel cells lie in their applicability to heavy machinery, requiring high power density. However, the commercial membrane electrode assembly (MEA) with polytetrafluoroethylene binders in catalyst layer (CLs) has low cell performance. In this study, hydrophobic mesoporous silica (HM-SiO2) is successfully prepared and incorporated into CL with a novel bipyridyl polybenzimidazole (Py-PBI) binders reported in our previous work. The HM-SiO2 can partially react with phosphoric acid (PA) to generate colloidal silicophosphoric acid. This can immobilize PA within the CL, prevent it from poisoning the platinum-carbon (Pt–C) catalyst. Owing to the partial dissolution of HM-SiO2, the HM-SiO2 is advantageous for decreasing the resistance to oxygen and steam transport. The MEA with 15 wt% HM-SiO2 exhibits a peak power density of 714 mW cm−2 at 160 °C under 0.6 mg cm−2 Pt, which is a considerable improvement compared with that with commercial binder (260 mW cm−2). The MEA with 15 wt% HM-SiO2 also demonstrates excellent stability in long-term stability test. Controlling PA distribution and gas transport by using HM-SiO2 is an effective strategy for improving the cell performance.