Synthesis, Structure and Electrical Properties of Mo‐doped CeO₂–Materials for SOFCs

Abstract

In this paper, we report the synthesis, structure and electrical conductivity of Mo‐doped compounds with a nominal chemical formula of Ce1–xMoxO2+δ (x = 0.05, 0.07, 0.1) (CMO). The formation of fluorite‐like structure with a small amount of Ce8Mo12O49 impurity (JCPDS Card No. 31‐0330) was confirmed using a powder X‐ray diffraction (PXRD). The fluoride‐type structure was retained under wet H2 and CH4 atmospheres at 700 and 800 °C, while diffraction peaks due to metal Mo were observed in dry H2 under the same condition. AC impedance measurements showed that the total conductivity increases with increasing Mo content in CMO, and among the investigated samples, Ce0.9Mo0.1O2+δ exhibited the highest electrical conductivity with a value of 2.8 × 10–4 and 5.08 × 10–2 S cm–1 at 550 °C in air and wet H2, respectively. The electrical conductivity was found to be nearly the same, especially at high temperatures, in air, O2 and N2. Chemical compatibility of Ce0.9Mo0.1O2+δ with 10 mol‐% Y2O3 stabilised ZrO2 (YSZ) and Ce0.9Gd0.1O1.95 (CGO) oxide ion electrolytes in wet H2 was evaluated at 800–1,000 °C, using PXRD and EDX analyses. PXRD showed that CMO was found to react with YSZ electrolyte at 1,000 °C. The area specific polarisation resistance (ASPR) of Ce0.9Mo0.1O2+δ on YSZ was found to be 8.58 ohm cm2 at 800 °C in wet H2.

Novel Nd2WO6-type Sm2−xAxM1−yByO6−δ (A=Ca, Sr; M=Mo, W; B=Ce, Ni) mixed conductors

“…The partial reduction of SMO in CH 4 compared to wet H 2 may be due to difference in the oxygen partial pressure. Interestingly, unlike Mo-doped CeO 2 [15], we did not see the peaks due to metallic Mo in the investigated compounds after chemical stability in H 2 , which is consistent with literature [17,18].…”

“…S7 (see supporting information), respectively. A spike at 1 MHz due to an instrument artifact was found to be consistent with our earlier studies [15,37,38], hence the data points above 1 MHz were omitted for clarity in the figures. In air, the impedance plots can be modeled using an equivalent circuit consisting of three series of parallel resistance-constant phase element contributions (R b CPE b )(R gb CPE gb ) (R el CPE el ) where R b , CPE b , R gb , CPE gb , R el , and CPE el represent bulk resistance, constant phase element due to bulk, grain-boundary resistance, constant phase element due to grain-boundary, electrode resistance and CPE due to electrode effect, respectively.…”

“…In our earlier work, we reported Mo, and Mo + rare earth-doped ceria as SOFC anode materials [15,16]. These compounds exhibited about three orders of magnitude higher total conductivity in wet H 2 compared to that in air at low temperatures due to the reduction of Mo VI and Ce IV .…”

Preparation, structure and electrical conductivity of the pyrochlore-type phase Sm2Zr2O7 codoped with bivalent magnesium and trivalent dysprosium cations

“…The grain resistance (R G ) and capacitance (C G ), and the grain-boundary resistance (R GB ) and capacitance (C GB ) of the electrolyte can be obtained in this way. From fitted results, at 673 K, the capacitance for the high frequency arc is determined to be in the order of pF, the intermediate frequency arc shows capacitance in the order of nF, and the low frequency arc exhibits capacitance in the order of F. These are typical values for the grain, grainboundary, and electrode contributions in the solid electrolyte [25]. In order to better understand the influence of magnesium and dysprosium cations codoping on the total conductivity of the Sm 2 Zr 2 O 7 pyrochlore, the intermediate frequency intercept to the Z axis is considered to determine the total resistance (R G + R GB ).…”

Modeling of Solid Oxide Fuel Cells with Particle Size and Porosity Grading in Anode Electrode

“…SOFCs show up to 60%, chemical to electrical efficiency in full scale trials [1][2][3]. They have also been shown to be fuel flexible and tolerant of impurities such as sulfur [4][5][6]. However, commercialization of SOFC has been hindered by its high operating temperature.…”