Evaluation Of Nano-structured Ir_(0.5)mn_(0.5)o_2 As A Potential Cathode For Intermediate Temperature Solid Oxide Fuel Cell

摘要

A novel Ir_(0.5)Mn_(0.5)O_2 cathode has been synthesized by thermal decomposition of mixed H_2IrCI_6 and Mn(NO_3)_2 water solution. The Ir_(0.5)Mn_(0.5)O_2 cathode has been characterized by XRD, field emission SEM (FESEM) and AC impedance spectroscopy. XRD result shows that rutile-structured Ir_(0.5)Mn_(0.5)O_2 phase is formed by thermal decomposition of mixed H_2IrCl_6 and Mn(NO_3)_2 water solution. FESEM micrographs show that a porous structure with well-necked particles forms in the cathode after sintering at 1000 ℃. The average grain size is between 20 and 30 nm. Two depressed arcs appear in the medium-frequency and low-frequency region, indicating that there are at least two different processes in the cathode reaction: charge transfer and molecular oxygen dissociation followed by surface diffusion. The minimum area specific resistance (ASR) is 0.67 Ω cm~2 at 800 ℃. The activation energy for the total oxygen reduction reaction is 93.7 kJ mol~(-1). The maximum power densities of the Ir_(0.5)Mn_(0.5)O_2 /LSGM/Pt cell are 43.2 and 80.7 mW cm~(-2) at 600 and 700 ℃, respectively.