Self-humidifying Pt-C/Pt-TiO₂ dual-catalyst electrode membrane assembly for proton-exchange membrane fuel cells

Abstract

A high-performance Pt-C/Pt-TiO2 dual-catalyst electrode was prepared and found to exhibit excellent water production and retention in self-humidifying proton-exchange membrane fuel cells. Different weight fractions of xPt-C/(1 x)Pt-TiO2 dual-catalyst layer were applied to both anode and cathode with fixed total Pt loadings of 0.2 mg/cm(2) and 0.3 mg/cm(2). The dependence of cell performance on the Pt-TiO2 content in dual-catalyst electrode was highly affected by the relative humidity (RH): When the RH was lower than 60%, the cell performance was significantly affected by the Pt-TiO2 content. The ability to produce and retain water of the Pt-TiO2 catalyst layer on the anode side was very important for the zero-RH cell performance. A visual cell experiment clearly revealed that water production at the anode was highly dependent on the Pt-TiO2 content in the Pt-C/Pt-TiO2 dual layer on the anode side. A half dual layer experiment involving the Pt-TiO2 on the cathode side alone strongly suggested that zero-RH operation is impracticable. The Pt-TiO2 in the dual layer at the anode produces water consuming the H-2 and O-2 crossing the membrane from the cathode, resulting in excellent cell performance under zero RH. The Pt-C/Pt-TiO2 ratio must be optimized in terms of the water-production and retention ability.