Preparation and electrochemical properties of strontium doped Pr_2NiO_4 cathode materials for intermediate-temperature solid oxide fuel cells

摘要

Pr_(2_x)Sr_xNiO_4 (PSNO, × = 0.3, 0.5 and 0.8) cathode materials for intermediate-temperature solid oxide fuel cell (IT-SOFC) were synthesized by a glycine-nitrate process using Pr_6O_(11), Ni(NO_3)_2-6H_2O and SrCO_3 powders as raw materials. Phase structure of the synthesized powders was characterized by X-ray diffraction analysis (XRD). Microstructure of the sintered PSNO samples was observed and thermal expansion coefficient (TEC) and electrical conductivity were investigated. Electrochemical impedance spectroscopy (EIS) measurement of the PSNO materials on Sm_(0.2)Ce_(0.8)O_(1.9) (SCO) electrolyte was carried out, and single cells based on the PSNO cathodes were also assembled and their performances were tested. The results show that the synthesized PSNO powders have pure K_2NiF_4-type structure and the PSNO materials are chemically stable with Sm_(0.2)Ce_(0.8)O_(1.9) (SCO) electrolyte. The sintered PSNO samples have porous and fine microstructure with pore size smaller than 1 nm. Average thermal expansion coefficient of the PSNO materials is about 12-13 × 1O~6 K~(-1) at 200-800 ℃ and the electrical conductivity is in the range of 70-120 Scm~(-1) at 800 ℃. Area specific resistance (ASR) of the Pr_(2- x)Sr_xNiO_4 materials on SCO electrolyte is 0.407 Ωcm~2, 0.126 Ωcm~2 and 0.112 Ωcm~2 for × = 0.3, 0.5 and 0.8 at 800 ℃, respectively. Maximum open circuit voltage (OCV) and power density of the single NiO-SCO/SCO/PSNO cells are 0.75 V and 298 mWcm ~(-2) at 700 ℃, respectively, which indicates that Pr_(2 _x)Sr_xNiO_4 may be a potential cathode material for IT-SOFC.