Particle size effect upon oxygen reduction on PAFC's cathodes: An unifying approach

The influence of Pt particle size on the activity of oxygen reduction in phosphoric acid fuel cells was investigated. The O2 reduction performance of a series of cathodes (40% Teflon, sintering temperature = 340°C) made from catalysts of different metal surface areas (MSA from TEM = 20 ÷ 200 m2/gpt and intercrystalline separation (IS, from 12 to 310 nm) was determined in terms of specific activity (SA, ?A/cm2pt) and mass activity (MA, mA/mgpt), in 98% H3PO4 at T = 170°C. MSA was made to vary by changing preparative conditions: all electrocatalysts were made with constant Pt loading (20% Pt/C) on a carbon with a BET surface area of 950 m2/g. From cyclic voltammetry measurements on the electrodes, the electrode platinum working area (EPWA) was measured and the Pt utilization was found to be linearly related to the percentage of phosphoric acid occupation, an index of morphological-absorptive characteristics of the electrodes.