Pore Structure and Durability Improvement of CNovel<sup>®</sup> Mesoporous Carbon as a Support Material for Pt Catalysts in Polymer Electrolyte Fuel Cells
Hideo Daimon, Hideo Inoue, Minoru Inaba
Abstract
Pore structure of mesoporous carbon (MPC, CNovel®) as support material for Pt catalysts in polymer electrolyte fuel cells and durability improvement of MPC by heat-treatment were investigated. Because the primary particle size of MPC is ∼2 μm, MPC is bead-milled to about 800 nm. Surface area of MPC is 1338 m 2 g −1 , which is comparable to that of conventional porous carbon support KB-600JD 1350 m 2 g −1 , while internal surface area of MPC is 1253 m 2 g −1 , much larger than that of KB-600JD (716 m 2 g −1 ). Mesopore size distribution of MPC is narrower than that of KB-600JD, with central mesopore size of 4 nm. 3D-TEM analysis shows that MPC has much higher density of interconnected mesopores (2–6 nm) than KB-600JD, and cross-sectional scanning electron microscopy observations indicate that macropores (> 50 nm) coexist in MPC. These pore structures contribute to higher cell voltage of Pt/MPC over Pt/KB-600JD in the entire current density region. MPC support is heat-treated at 1800 °C–2400 °C in Ar to improve durability against high potentials (1.0–1.5 V vs RHE). Durability of Pt/MPC is higher than that of Pt/KB-600JD and monotonically improves with increasing heat-treatment temperature. MPC support maintains high surface area of 800 m 2 g −1 even after heat-treatment at 2200 °C.