Ionic transport modification in proton conducting BaCe0.6Zr0.3Y0.1O3−δ with transition metal oxide dopants

Abstract

Proton conducting BaCe0.6Zr0.3Y0.1O3-δ (BCZY63) pellets were fabricated by the solid-state reactive sintering method whereby a small extra amount of a metal oxide additive (5 mol%) was included in the precursor mixture before sintering. The effect of the addition of six different metal oxide additives (CuO, ZnO, Fe2O3, MnO2, PdO, and Cr2O3) on the transport properties of BCZY63 was investigated. Although most additives (e.g. ZnO, Fe2O3, MnO2, Cr2O3) led to a decrease (sometimes minor) in conductivity, CuO and PdO dopants yielded an increase in total conductivity compared to the BCZY63 control. The enhancement in the total conductivity is found to be related to two factors: 1) the additive can act as a sintering aid to produce larger grain size; 2) substitutional doping of the BCZY structure by metal ions from additives can lead to increased bulk proton concentration. Due to its excellent sinterability and moderately improved proton conductivity, CuO-doped BCZY63 was subsequently applied as the dense electrolyte layer in protonic ceramic fuel cells utilizing a recently developed single firing step fabrication technique to produce high quality single cells that showed exceptional performance and long-term stability.

Structural and Electrochemical Properties of Dense Yttria-Doped Barium Zirconate Prepared by Solid-State Reactive Sintering

“…A is the area of the sample; L is the thickness of the sample; k is the Boltzmann's constant; and e is the electron charge. It is generally believed that the arc in the high-frequency region exhibits a value for the proton-conducting oxide grain (C =~10 −11 F), and that the arc in the intermediate-frequency region exhibits a value for the grain boundary (C =~10 −9 F) [6][7][8]13,30,31] that is in agreement with this study. The bulk dielectric constants of BZY obtained in this study were higher than those (37-155) reported in the literature [13,31,33,34].…”

“…Therefore, in the present study, proton conductivity was measured under a reducing wet atmosphere (3% H 2 in Ar and pH 2 O = 0.03 atm). Cole-Cole plots are typically used to determine the grain (R b and CPE b ), grain boundary (R gb and CPE gb ), and electrode (R elec and CPE elec ) contributions [6][7][8]13,30,31]. Figure 6 shows the Cole-Cole plots obtained for the sintered BZY samples.…”

Gas Humidification Impact on the Properties and Performance of Perovskite‐Type Functional Materials in Proton‐Conducting Solid Oxide Cells

“…From the macroscopic viewpoint, the grain boundary resistance of the electrolytes can be reduced by increasing the grain size or decreasing the grain boundary density. There are two well‐known strategies to facilitate the grain growth such as the use of nanosized materials with enhanced sinterability or the addition of sintering additives . Both of these methods are useful for developing high‐efficient electrochemical devices.…”

Synthesis and Evaluation of Ni Catalysts Supported on BaCe0.5Zr0.3−xY0.2NixO3−δ with Fused-Aggregate Network Structure for the Hydrogen Electrode of Solid Oxide Electrolysis Cell

“…The proton reduction reaction to hydrogen is the rate-determining step in the hydrogen evolution reaction [43]. The slight amount of Ni doping in the BCZY phase enhances the electronic conductivity while maintaining the proton conductivity [31][32][33][34], which led to the enhancement of the current densities obtained using the Ni/BCZYN (x = 0.03) CLs. Moreover, in earlier papers, Ni dispersed on mixed conductors was found to lead to enhancement of the ERZ around the Ni catalyst particles with increasing electronic conductivity [24][25][26].…”

“…The CCL of µm-sized Ni-MPEC oxide cermet is formed on top of the CL to supply a highly electronically conductive layer, with high gas-diffusion rate from the separator (interconnect) to the CL, and an intimate contact between the separator and the CL. The slight amount of Ni doping in the proton-conducting oxide enhanced the electronic conductivity in the oxide [31][32][33][34], which was one of the most promising MPEC oxides for applications based on the above concept.…”