Effect of NiO Addition on the Sintering and Electrochemical Properties of BaCe0.55Zr0.35Y0.1O3-δ Proton-Conducting Ceramic Electrolyte

Abstract

Proton ceramic fuel cells offer numerous advantages compared with conventional fuel cells. However, the practical implementation of these cells is hindered by the poor sintering activity of the electrolyte. Despite extensive research efforts to improve the sintering activity of BCZY, the systematic exploration of the utilization of NiO as a sintering additive remains insufficient. In this study, we developed a novel BaCe_0.55Zr_0.35Y_0.1O_3-δ (BCZY) electrolyte and systematically investigated the impact of adding different amounts of NiO on the sintering activity and electrochemical performance of BCZY. XRD results demonstrate that pure-phase BCZY can be obtained by sintering the material synthesized via solid-state reaction at 1400 °C for 10 h. SEM analysis revealed that the addition of NiO has positive effects on the densification and grain growth of BCZY, while significantly reducing the sintering temperature required for densification. Nearly fully densified BCZY ceramics can be obtained by adding 0.5 wt.% NiO and annealing at 1350 °C for 5 h. The addition of NiO exhibits positive effects on the densification and grain growth of BCZY, significantly reducing the sintering temperature required for densification. An anode-supported full cell using BCZY with 0.5 wt.% NiO as the electrolyte reveals a maximum power density of 690 mW cm^-2 and an ohmic resistance of 0.189 Ω cm² at 650 °C. Within 100 h of long-term testing, the recorded current density remained relatively stable, demonstrating excellent electrochemical performance.

Keywords: BaCe0.55Zr0.35Y0.1O3-δ electrolyte; NiO sintering additive; electrochemical performance; proton ceramic fuel cells; sintering activity.

Figure 1

X-ray diffraction analysis of BCZY powder sintered at 900–1400℃ for 10h. (a) XRD patterns of BCZY electrolyte powder sintered at 900–1400 °C for 10 h, (b) phase composition and content of BCZY electrolyte powder sintered at 900–1400 °C for 10 h, and (c) refined XRD pattern of pure-phase BCZY obtained after sintering at 1400 °C for 10 h.

Figure 2

(a) XRD diffraction patterns of BCZY electrolyte pellets sintered at 1350 °C for 5 h with varying amounts of NiO and an enlarged region in the range of 27–31°. Refinement results for the XRD patterns of samples: (b) BCZY-0, (c) BCZY-0.5, (d) BCZY-1.0, (e) BCZY-1.5, and (f) BCZY-2.0.

Figure 3

Sintering behavior test of BCZY electrolyte pellets with different amounts of NiO added. (a) Relative density of BCZY electrolyte pellets with different amounts of NiO sintered at 1300–1550 °C for 5 h, (b) shrinkage curves of BCZY and BCZY with different amounts of NiO, (c) shrinkage rate of electrolyte pellets after sintering at 1350 °C for 5 h, and (d) thermal expansion curves of BCZY and BCZY with different NiO addition amounts.

Figure 4

SEM images of BCZY electrolyte pellets with different amounts of NiO added after sintering at 1350 °C for 5 h. (a) BCZY-0, (b) BCZY-0.5, (c) BCZY-1.0, (d) BCZY-1.5, (e) BCZY-2.0, (f) statistical diagram of grain size, and (g) SEM–EDS mapping results for BCZY-1.0.

Figure 5

Electrical conductivity of BCZY, BCZY-0.5, and BCZY-1.0 in atmospheres of air (a) and wet hydrogen (b). Arrhenius curves in the air (c) and humidified hydrogen (d) atmospheres.

Figure 6

Single cell output performance diagram and proton transport diagram. (a) the single cell I–V and I–P diagrams of NiO–BCZY/BCZY-x (x = 0, 0.5, 1.0, 1.5, 2.0)/BCZY–LSCF with a cell structure; (b) EIS diagram; (c) performance comparison of BCZY, BCZY-0.5, and BCZY-1.0; (d) scheme for proton transportation in BCZY, BCZY-0.5 and BCZY-excessive NiO.

Figure 7

(a) I–V and I–P diagrams of the single cell with a structure of NiO-BCZY/BCZY-0.5/BCZY–LSCF at 600–700 °C, (b) EIS diagram, (c) the corresponding EIS of the complete single cell measured under open circuit conditions, (d) cross section view of the single cell after testing, (e) comparison of MPDs of SOFCs based on H⁺ and O²⁻ conductors [29,40,41,42,43,44,45,46,47,48,49], and (f) durability test of the cell at 650 °C and 0.7 V.