Nanocomposites: A New Opportunity for Developing Highly Active and Durable Bifunctional Air Electrodes for Reversible Protonic Ceramic Cells

Abstract

Reversible protonic ceramic cells (RePCCs) can facilitate the global transition to renewable energy sources by providing high efficiency, scalable, and fuel‐flexible energy generation and storage at the grid level. However, RePCC technology is limited by the lack of durable air electrode materials with high activity toward the oxygen reduction/evolution reaction and water formation/water‐splitting reaction. Herein, a novel nanocomposites concept for developing bifunctional RePCC electrodes with exceptional performance is reported. By harnessing the unique functionalities of nanoscale particles, nanocomposites can produce electrodes that simultaneously optimize reaction activity in both fuel cell/electrolysis operations. In this work, a nanocomposite electrode composed of tetragonal and Ruddlesden–Popper (RP) perovskite phases with a surface enriched by CeO2 and NiO nanoparticles is synthesized. Experiments and calculations identify that the RP phase promotes hydration and proton transfer, while NiO and CeO2 nanoparticles facilitate O2 surface exchange and O2‐ transfer from the surface to the major perovskite. This composite also ensures fast (H+/O2‐/e‐) triple‐conduction, thereby promoting oxygen reduction/evolution reaction activities. The as‐fabricated RePCC achieves an excellent peak power density of 531 mW cm‐2 and an electrolysis current of −364 mA cm‐2 at 1.3 V at 600 °C, while demonstrating exceptional reversible operation stability of 120 h at 550 °C.

Advanced Materials for Thin‐Film Solid Oxide Fuel Cells: Recent Progress and Challenges in Boosting the Device Performance at Low Temperatures

“…With the promoted hydration and proton conductivity caused by the RP phase, an attractive performance of 0.53 W cm −2 at 550 °C was obtained. [187] Shi et al also reported the synergetic effect of a hetero-phase. The nominal composition of LaSr 2.7 Co 1.5 Fe 1.5 O 10−δ was formed by mixing a single perovskite of LaSr 2 Co 1.5 Fe 1.5 O 10−δ and an RP LaSr 3 Co 1.5 Fe 1.5 O 10−δ phase.…”

“…With the promoted hydration and proton conductivity caused by the RP phase, an attractive performance of 0.53 W cm −2 at 550 °C was obtained. [ 187 ] Shi et al. also reported the synergetic effect of a hetero‐phase.…”

Functionalized Metal‐Supported Reversible Protonic Ceramic Cells with Exceptional Performance and Durability

“…[26] XRD analysis of the synthesized SCFN powder (Figure S2, Supporting Information) suggests that, in agreement with previous studies, SCFN consisted of two major perovskite phases (T-SCFN and RP-SCFN) and two minor oxide phases (NiO and CeO 2 ). [22,25] The cross section of the reduced MS-RePCC was imaged by scanning electron microscopy (SEM), as shown in Figure 2d. The porous NiÀFe alloy support layer (Figure S3, Supporting Information) was 650 μm thick and made tight contact with the 90 μm-thick NiÀBZCYYb layer.…”

“…The fabricated MS-RePCC was also tested for reversible performance. The IÀV curves were measured in the temperature range of 600À700 C by feeding pure H 2 [25,34] and air with 3 vol% H 2 O to the fuel and air electrodes, respectively (Figure 4c). It can be observed that the current densities at 1.3 V were À428, À331, and À124 mA cm À2 at 700, 650, and 600 C, respectively.…”

“…As a comparison, the degradation rate of an analogous anode‐supported cell (Ni−BZCYYb|BZCYYb|SCFN) prepared by one of the coauthors was measured to be ≈17.78% kh −1 . [ 25 ] Furthermore, the fabricated MS‐RePCC could be operated reversibly for 50 h (25 cycles) at 600 °C without noticeable degradation.…”