Experimental and DFT study of undoped and A/B-site doped Nd1-xAxMn1-yAlyO3 (A = Ca, Sr, Ba) perovskites for thermochemical CO2 conversion

The development of efficient nonstoichiometric redox materials for solar-driven H₂O/CO₂ splitting via two-step thermochemical cycles requires optimization of redox thermodynamics, kinetics, and material stability. This study investigates neodymium manganite perovskites (Nd 1-x A x Mn 1-y Al y O 3 ) as oxygen carriers doped in the A-site (Ca, Sr, Ba) and B-site (Al), and synthesized via a modified Pechini method to achieve a porous and reactive microstructure. Thermogravimetric analysis revealed a critical trade-off between the extent of reduction and reoxidation efficiency, with Nd 0.8 Sr 0.2 Mn 0.8 Al 0.2 O 3 emerging as a top-performing formulation. It demonstrated strong CO₂-splitting activity, near-complete reoxidation, and competitive performance compared to benchmark ceria. Kinetic studies showed that Nd 0.6 Ca 0.4 MnO 3 and Nd 0.8 Sr 0.2 Mn 0.8 Al 0.2 O 3 follow phase-boundary-controlled kinetics, while other compositions suffered from diffusion limitations. DFT calculations further validated these findings, showing that 40% Ca or Sr doping yields optimal oxygen vacancy formation energies for thermochemical application. Structural analysis further linked enhanced fuel production to non-ideal intrinsic strain, as revealed by Williamson-Hall plots and elastic mechanical calculations via DFT. These results suggest that defect-induced lattice distortions promote redox activity. This work provides critical insights into the design of high-performance perovskites through balanced dopant selection, redox kinetics, and strain engineering for enhanced solar fuel production. • Nd 1-x A x Mn 1-y Al y O 3 (A = Ca, Sr, Ba) perovskites were engineered for CO 2 thermochemical splitting. • Nd 0.8 A 0.2 Mn 0.8 Al 0.2 O 3 achieved intermediate redox yield with fast kinetics and near-complete reoxidation. • 40% Ca or Sr doping delivered optimal oxygen vacancy formation energies (DFT). • Lattice strain and defect engineering enhanced fuel production and redox stability. • Phase-boundary-controlled kinetics enabled faster cycling and higher CO 2 conversion.