Insights into the Redox Performance of Non–stoichiometric Lanthanum Manganite Perovskites for Solar Thermochemical CO_2 Splitting

摘要

Perovskite structured mixed metal oxides are one category of redox materials that recently demonstrated high potential for solar fuel production from thermochemical H_2O/CO_2 splitting. Substituted lanthanum manganite perovskite was previously found to be one of the most suitable candidates among the perovskite family, owing to its unique redox properties. How- ever, the effect of synthesis method and cationic substitutions in A and B-sites of ABO_3 perovskite need to be elucidated. Herein, a systematic study was performed by implementing various synthetic strategies such as solid-state, pechini process, glycine combustion or glucose-assisted methods, to obtain Lax Sr~(1-x)MnO_3 (LSM) as a single phase and to determine the effect of synthesis method on the redox efficiency and performance stability for CO_2 splitting. The results indicated that the materi- als synthesized by the pechini method were the most reactive among the series, with a stable CO production of ~260 mmol.g~(-1) for x=0.5. Also, various pure phase A and B-site sub- stituted perovskites were synthesized by the pechini method to study the effect of such substitutions on the fuel yield of these materials. Y/Ca/Ba A-site and Al/Fe B-site substitutions in (La,Sr) MnO_3 did not enhance the redox cycling capability when com- pared with LSM. It was observed that Sr was the best A-site substituent and the presence of single Mn cation alone in B- site was the most suitable option for promoting CO_2-splitting activity. Further, the effect of the addition of promotional agents was explored and enhancement of CO evolution was observed when compared to pure LSM.