Efficient reversible CO/CO2 conversion in solid oxide cells with a phase-transformed fuel electrode

Abstract

The reversible solid oxide cell (RSOC) is an attractive technology to mutually convert power and chemicals at elevated temperatures. However, its development has been hindered mainly due to the absence of a highly active and durable fuel electrode. Here, we report a phase-transformed CoFe-Sr 3 Fe 1.25 Mo 0.75 O 7−δ (CoFe-SFM) fuel electrode consisting of CoFe nanoparticles and Ruddlesden-Popper-layered Sr 3 Fe 1.25 Mo 0.75 O 7−δ (SFM) from a Sr 2 Fe 7/6 Mo 0.5 Co 1/3 O 6−δ (SFMCo) perovskite oxide after annealing in hydrogen and apply it to reversible CO/CO 2 conversion in RSOC. The CoFe-SFM fuel electrode shows improved catalytic activity by accelerating oxygen diffusion and surface kinetics towards the CO/CO 2 conversion as demonstrated by the distribution of relaxation time (DRT) study and equivalent circuit model fitting analysis. Furthermore, an electrolyte-supported single cell is evaluated in the 2:1 CO-CO 2 atmosphere at 800°C, which shows a peak power density of 259 mW cm −2 for CO oxidation and a current density of −0.453 A cm −2 at 1.3 V for CO 2 reduction, which correspond to 3.079 and 3.155 mL min −1 cm −2 for the CO and CO 2 conversion rates, respectively. More importantly, the reversible conversion is successfully demonstrated over 20 cyclic electrolysis and fuel cell switching test modes at 1.3 and 0.6 V. This work provides a useful guideline for designing a fuel electrode through a surface/interface exsolution process for RSOC towards efficient CO-CO 2 reversible conversion.

Tailoring Sr2Fe1.5Mo0.5O6−δ with Sc as a new single-phase cathode for proton-conducting solid oxide fuel cells

“…As a result, developing SOFCs that operate at lower temperatures (such as 700°C) is extremely desirable [4,5]. The development of highly conductive electrolyte materials and cathode materials with good catalytic activity at intermediate temperatures is required to reduce the SOFC working temperature [6,7]. In terms of electrolyte materials, proton-conducting oxides have been proposed as electrolytes for SOFCs in recent decades due to their high ionic conductivity at 600°C [8][9][10].…”

Exsolved metallic iron nanoparticles in perovskite cathode to enhance CO2 electrolysis

“…In contrast, lanthanum chromate-based perovskite oxides possess high chemical stability either in oxidizing or in reducing atmosphere [20][21][22][23]. However, efficient CO 2 conversion still remains a big challenge with chromate oxide cathodes and this is mainly related to their limited catalytic activity [24].…”

Investigating the effect of rGO on microstructural and electrical properties of La0.9Sr0.1Ga0.8Mg0.2O3 in intermediate temperature SOFCs

“…cations on the conductivity of the doped La site in LSGM and concluded that total conductivity was minimized and the magnitude relationship of conductivity was as follows: Nd 3+ > Sm 3+ > Gd 3+ > Y 3+ > Yb 3+ . [54][55][56][57][58][59] A decrease in conductivity is associated with a decrease in the geometric tolerance factor of the LSGM crystal structure. Some researchers have put in a lot of effort to improve the conductivity of LSGM through doping various cations including Fe 3+ , Co 3+ , Ni 2+ , Cu 2+ , Mn 2+ , Ti 2+ , Cr 2+ , and Al 3+ into the Ga site.…”