Improving Electrochemical Oxidation/Reduction Kinetics in Single-Component Solid Oxide Cells through Synergistic A-Site Defects and Anion Doping

Abstract

Solid oxide fuel/electrolysis cells (SOFCs/SOECs) have emerged as promising technologies for reversibly converting chemical and electrical energy. Here, we propose a synergistic approach involving the introduction of A-site defects and anion doping in the perovskite La0.6Sr0.4Co0.2Fe0.8O3‑δ (LSCF) oxide to enhance its electrochemical oxidation/reduction kinetics as an electrode material in single-component SOFCs/SOECs. By creating an A-site deficient and F-doped oxyfluoride, designated as (La0.6Sr0.4)0.95Co0.2Fe0.8F0.1O2.9‑δ (F-(LS)0.95CF), we effectively lower the valence state of both Co and Fe elements, leading to a higher concentration of oxygen vacancies. This synergistic approach yields a remarkable approximately 5-fold increase in the oxygen surface exchange coefficient (k chem) and a 50% increase in the bulk diffusion coefficient (D chem) at 700 °C, when compared with LSCF. The resulting F-(LS)0.95CF-based single cell demonstrates approximately a 100% higher maximum power density for SOFC operation and a 60% higher current density at 1.3 V for SOEC operation. These improvements are further supported by lower polarization resistances observed in symmetrical cells with F-(LS)0.95CF. Furthermore, detailed investigations into the reaction kinetics reveal distinctive behaviors for the hydrogen oxidation reaction when comparing LSCF to F-(LS)0.95CF as the electrode material. Specifically, for LSCF, the rate-limiting step is the adsorption and dissociation of H2, while for F-(LS)0.95CF, it primarily involves a charge-transfer reaction. Conversely, for the oxygen reduction reaction, regardless of the electrode material being LSCF or F-(LS)0.95CF, the rate-limiting step consistently involves the reduction of oxygen atoms to O–.

Semiconductor Heterostructure (SrFe0.3TiO3-ZnO) Electrolyte with High Proton Conductivity for Low-Temperature Ceramic Electrochemical Cells

“…A schematic of the reactions and proton transport involved in the water electrolysis cell is shown in Figure a. Further, the current density attained is higher than in the previously published reports. − Also, the electrolysis cell of composite heterostructure SFT-ZnO has delivered high current densities of 1.85, 1.5, 1.18, and 0.35 A cm –2 with different voltages of 2, 1.8, 1.6, and 1.3 V at 520 °C (see Figures b and e).…”

High-Performance and Robust Composite Cathode via W Doping-Induced Phase Separation for Proton Ceramic Fuel Cells

“…The signal of W at the binding energy of ∼36 eV in all samples is observed, matching well with the above results. Figure b,c illustrates the fitted XPS curves of Co 2p and Fe 2p in all samples, respectively. − It can be seen that the average valences of Co and Fe for SCFW0.03 in comparison to SCFW0.01 are almost unchanged, while they are sharply decreased for the SCFW0.05 composite. It suggests that a higher content of W doping cannot change the average valence of the oxide surface, and DP phase formation enhanced oxygen vacancy concentration inside the material, which is beneficial for oxygen ion migration.…”

High-Performance Low-Temperature Solid Oxide Fuel Cell with a Pt@C–Ni0.8Co0.15Al0.05LiO2−δ Composite Cathode

“…Chen et al prepared nanostructured GDC from cerium nitrate and gadolinium nitrate using the sol–gel method with symmetric electrodes of NCAL attached to nickel foam with a power density of 591.8 mW cm –2 . Tong et al proposed an A-site defect and anionic doping introduced into the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ chalcogenide structure to enhance the oxidation/reduction kinetic process of the electrode materials in SOFCs/solid electrolysis cells (SOECs).…”