Advanced Fuel Cell Based on Perovskite La–SrTiO₃ Semiconductor as the Electrolyte with Superoxide-Ion Conduction

Abstract

A solid oxide fuel cell's performance is largely determined by the ionic-conducting electrolyte. A novel approach is presented for using the semiconductor perovskite LaSrTiO (LST) as the electrolyte by creating surface superionic conduction, and the authors show that the LST electrolyte can deliver superior power density, 908.2 mW cm at just 550 °C. The prepared LST materials formed a heterostructure, including an insulating core and a superionic conducting surface layer. The rapid ion transport along the surfaces or grain boundaries was identified as the primary means of oxygen ion conduction. The fuel cell-induced phase transition was observed from the insulating LST to a super O conductivity of 0.221 S cm at 550 °C, leading to excellent current and power outputs.

Electrochemical mechanisms of an advanced low-temperature fuel cell with a SrTiO3 electrolyte

“…1,8,9 We found in a previous study that the maximum power density of a SIFC with a 0.5 mm La 0.25 Sr 0.75 TiO 3 (LST) layer as the electrolyte and nickel foam coated NCAL as the symmetrical electrode could reach 908 mW cm À2 at 550 C in H 2 /air. 1 The excellent catalytic activity and high conductivity of Ni foam coated NCAL electrodes for the HOR and the ORR play an important role in achieving high performance with the LST electrolyte cell. 13 Asghar et al used a composite of wide bandgap lithium-nickel-zinc-oxide (LNZ) and gadolinium-doped-ceriumoxide (GDC) as the electrolyte to prepare two kinds of cells with Au/GDC-LNZ/Au and Ni foam-NCAL/GDC-LNZ/NCAL-Ni foam structures.…”

“…Solid oxide fuel cells (SOFCs) with nanocomposites and/or nanocrystalline oxides as electrolytes have attracted a lot of attention. [1][2][3][4][5][6] The electrolyte of the cell is usually a nanocomposite of two oxides or a single nanocrystalline oxide material, such as a mixture of Gd-doped CeO 2 (GDC) and Li-Ni-Zn oxide (LNZ), or a single nano-GDC, which can be used as an electrolyte. 3,7 In this kind of cell structure, the electrolyte is usually made of a semiconductor material, for which reason this type of fuel cell is also called a semiconductor ionic fuel cell (SIFC).…”

“…3,7 In this kind of cell structure, the electrolyte is usually made of a semiconductor material, for which reason this type of fuel cell is also called a semiconductor ionic fuel cell (SIFC). 1,2,[8][9][10][11][12] Unlike traditional SOFC cermet anodes (Ni/YSZ, Ni/GDC) and ceramic oxide cathodes (LSM, LSCF, etc. ), lithium containing metal oxides such as Ni 0.8 Co 0.15 Al 0.05 LiO 2 (NCAL) are commonly used as electrodes in SIFCs.…”

“…1,5,[8][9][10][11][12][13] A SIFC shows better electrochemical performance in the low temperature range (300-600 C) than a traditional SOFC with the same electrolyte thickness. 1,8,9 We found in a previous study that the maximum power density of a SIFC with a 0.5 mm La 0.25 Sr 0.75 TiO 3 (LST) layer as the electrolyte and nickel foam coated NCAL as the symmetrical electrode could reach 908 mW cm À2 at 550 C in H 2 /air. 1 The excellent catalytic activity and high conductivity of Ni foam coated NCAL electrodes for the HOR and the ORR play an important role in achieving high performance with the LST electrolyte cell.…”

“…7 The ionic conductivity of a LST electrolyte is high, e.g. 0.22 S cm À1 at 550 C. 1 The ionic conductivity of eutectic mixtures composed of Ce 0.85 Sm 0.15 O 2 (SDC) and Na 2 CO 3 , Li 2 CO 3 , K 2 CO 3 (NLK) could even reach >0.5 S cm À1 at 550 C. 14,15 With BaZr 0.9 Y 0.1 O 3Àd (BZY), which is an electrolyte material used in traditional SOFCs, a nanocrystalline electrolyte had an ionic conductivity of 0.33 S cm À1 at 550 C. The ionic conductivity of these electrolytes is much higher than that of the traditional YSZ, GDC, LSGM, and BZY electrolytes densied by sintering at temperatures higher than 1400 C. [16][17][18] For example, the conductivity of GDC and BZY is below 0.05 S cm À1 at 550 C. 16,19,20 The new electrolyte structure reported here offers an alternative for improving the low temperature ionic conductivity of SOFC materials.…”