Abstract
SmBaCo2O5+δ (SBC) was studied as cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The crystal structure, thermal expansion behavior, and electrochemical performance with long-term operation of SBC were characterized. An orthorhombic layered perovskite structure was observed in SBC cathode by a GSAS program for refinement. The average thermal expansion coefficient (TEC) is 21.6 x 10-6K-1 in the temperature range of 100oC-800oC. For long-term testing, the polarization resistance of SBC cathode increases gradually from 25.77 Ω cm2 for 2 h to 38.77 Ω cm2 for 96 h at 600°C, and an increasing-rate for polarization resistance is around 13,8% h-1. Based on the electrochemical properties, SBC cathode with mixed ionic and electronic conductor (MIEC) behavior is a potential cathode for intermediate temperature solid oxide fuel cells based on a SDC electrolyte.
Highlights
Fuel cell is an electrochemical device that converts chemical energy into electrical energy with high efficiency and low pollutant emissions [1, 2]
A part of the smaller Co4+ were reduced to larger Co3+ or Co2+ with a loss of oxygen, C3+ ions are easy to transit from low-spin to high-spin state [14,21,22,23]
With increasing the testing time, the following slow degradation in the mixed ionic and electronic conductor (MIEC)-cathode performance may be several possible mechanisms such as (1) the grain size of SBC may coarsen [25], and (2) inter-diffusion may occur between SBC and SDC interface [26]. 3.4 SEM images The cathode microstructure is closely related to the electron and oxygen transportation, the reaction kinetics, charge transport, and mass transport preprocess
Summary
Fuel cell is an electrochemical device that converts chemical energy into electrical energy with high efficiency and low pollutant emissions [1, 2]. Intermediate-temperature (600-800°C) solid oxide fuel cells (IT-SOFCs) have been intensively investigated for both centralized and distributed power generations in the past decades [3,4,5,6]. High performance and reliable for IT-SOFCs still remain a big challenge, mainly due to the sluggish oxygen surface kinetics at the electrolyte surface and reluctant oxygen reduction reaction (ORR) activity in the cathode [6]. The development of new cathodes with high-electrocatalytic activity for the oxygen-reduction reaction is critical for intermediate-temperature solid oxide fuel cells (ITSOFCs) [4, 5]. To achieve a guarantee of reliability, the examination of degradation mechanisms of SOFCs during long-term operation is necessary. The electrochemical properties with long-term testing of an SBC cathode on SDC electrolyte were analyzed over the intermediate temperature (600-800oC)
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