Fly ash to improve density and ionic conductivity of solid oxide cell electrolytes

Abstract

With a view to the industrialization of solid oxide cells (SOCs) consisted of solid-oxide fuel cells (SOFCs) and solid-oxide electrolysis cells (SOECs), fly ash as a major industrial waste is proposed to improve density and ionic conductivity of solid-oxide electrolyte. Based on state-of-the-art yttria-stabilized zirconia (YSZ) electrolyte, the YSZ-x fly ash (YSZ-x, x = 0, 0.1, 1, 5, and 10 wt%) composites are prepared as potential electrolytes via the traditional mechanical mixing method. After sintering at 1400°C for 10 h, all YSZ-x electrolytes exhibit a main unchanged cubic-fluorite phase. The relative density of YSZ-x electrolytes effectively increases with trace additive of fly ash and can reach over 96–98% (YSZ-0.1 and YSZ-1). The thermal expansion coefficients of YSZ-x electrolytes keep mostly unchangeable. The ionic conductivities of YSZ electrolyte can be dramatically improved by trace additive of fly ash (YSZ-0.1) from oxidizing to reducing atmospheres and achieved as high as 0.14 S.cm-1 at 800°C. In short, fly ash is successfully used to evaluate dust pollution of solid electrolytes in the process of solid oxide cell industrialization and to improve the performance, which opens doors to design advanced solid oxide cell materials.