Low-temperature solid oxide fuel cells (LT-SOFCs) have attracted increasing attention as next-generation energy conversion devices due to their reduced operating costs and enhanced durability. A major challenge in this field is the development of cathode materials capable of delivering high electrochemical activity at reduced temperatures. In this study, cerium-based quaternary perovskite oxides with the general formula Ca₀.₅Ce₀.₅MO₃ (M = Fe, Mn, and Ni) were successfully synthesized via a co-precipitation route and systematically evaluated as cathodes for LT-SOFC applications. Structural integrity and phase formation were confirmed by X-ray diffraction, while Raman and UV–Vis spectroscopy provided insight into lattice vibrations and electronic structure. Surface morphology, elemental distribution, and defect chemistry including oxygen vacancy concentration—were investigated using SEM and XPS analyses. Among the compositions studied, Ca₀.₅Ce₀.₅MnO₃ (CCMO) exhibited superior electrochemical performance, delivering an open-circuit voltage of 1.03 V and a peak power density of 874 mW cm−2 at 550 °C. Impedance and current–voltage measurements further revealed enhanced charge transport characteristics for CCMO, indicating favorable electrode kinetics. These findings highlight the strong potential of CCMO quaternary perovskite nanomaterials as efficient cathodes for high-performance LT-SOFCs.
The transient current of cyclic enzymatic amperometric biosensors results from the coupling of species diffusion, nonlinear Michaelis-Menten kinetics, and electrochemical product conversion at the electrode. Two previously established cyclic reaction mechanisms are compared here within a common dimensionless framework to determine how reaction topology controls product redistribution and electrode flux. The complete nonlinear systems are solved by the Generalized Integral Transform Technique (GITT) without kinetic linearization, with selected results additionally checked against a separately derived MOL/FDM spatial discretization and exact limiting-case solutions. The reference formulation assumes uniform enzyme activity, negligible external mass-transfer resistance, limiting electrochemical conversion at the electrode, equal effective diffusivities, and a common Michaelis constant. Reassessment of published homotopy perturbation method (HPM) expressions separates the effects of kinetic linearization, boundary representation, and series truncation. Within the investigated parameter range, the second enzymatic step produces the strongest differentiation between the mechanisms: at α = 10 and Da1 = 100, increasing Da2 from 1 to 300 raises the current by factors of 5.16 and 124.5 in Models 1 and 2, respectively. The central mechanistic result is that identical substrate depletion and total-product formation can coexist with markedly different product partitioning and electrode fluxes. Additional GITT calculations show that this structural identity does not require K1=K2 and remains valid when DP1 = DP2 ≠ DS, but is generally lost when DP1 ≠ DP2. The results therefore distinguish topology-controlled behavior from assumption-dependent predictions and provide nonlinear reference solutions for interpreting cyclic amperometric responses.
