Two-Step Thermochemical CO2 Splitting Using Partially-Substituted Perovskite Oxides of La0.7Sr0.3Mn0.9X0.1O3 for Solar Fuel Production

Abstract

We investigated, herein, the redox activity of partial substitution of the B-site in a series of lanthanum/strontium-manganese-based (LSM) perovskite oxide, La0.7Sr0.3Mn0.9X0.1O3 for solar two-step thermochemical fuel production using concentrated solar radiation as an energy source. We systematically investigated the effects of partial substitution in LaSrMnO3 in terms of their kinetics behavior, oxygen/CO productivity, thermal reduction/oxidation temperatures. Furthermore, repeatability was evaluated and compared among the samples prepared using the same procedure and studied using the same test method. We observed and evaluated the long-term thermal stability of the redox activity and valence variation of the constituting ionic species of the perovskite in the two-step thermochemical CO2 splitting. From the perspectives of superior activity and long-term repeatability, Ni-, Co-, and Mg-substituted LSM perovskites are promising for thermochemical two-step CO2/H2O splitting to produce synthetic gas.

Redox Performance and Optimization of the Chemical Composition of Lanthanum–Strontium–Manganese-Based Perovskite Oxide for Two-Step Thermochemical CO2 Splitting

“…Compared to the valence change of the Mn ions in the nonsubstituted sample, the valence change increased in the LSMCo0.35 sample. The result of the LSMCo0.35 sample agreed well with the result of the 10%Mg-substituted sample without a valence change in Mg in a previous study [53]. Table 6.…”

“…The best-performing samples in this study ranked at the highest level of both CO productivities compared to the reported substituted LSMs, where LSMCo0.35 exhibited the maximum CO productivity (533 µmol/g material) among the reported LSM perovskites. Compared to the authors' previous results marked with a triangle (LSMMg0.10, LSMCo0.10, and LSMNi0.10) [53], obtained under the same test conditions using the same methods and devices, the CO productivity of LSMCo0.35 was ~1.5 times higher. Other perovskite materials that are not LSM series, Sm 0.6 Ca 0.4 Mn 0.8 Al 0.20 O 3 [68], Sr 0.6 Ce 0.4 Mn 0.8 Al 0.2 O 3 [69], and Sm 0.6 Sr 0.4 MnO 3 [70], were studied for the thermochemical two-step CO 2 splitting cycle.…”

“…Figure 13b shows the CO productivities per gram of material and average value per duration. Previous data on the thermochemical two-step CO 2 splitting using LSM-based perovskites in a thermogravimetric reactor have been cited from the literature [29,[31][32][33]36,[39][40][41]45,47,53,67]. The best-performing samples in this study ranked at the highest level of both CO productivities compared to the reported substituted LSMs, where LSMCo0.35 exhibited the maximum CO productivity (533 µmol/g material) among the reported LSM perovskites.…”

“…Reactivity was examined using a thermogravimetric (TG) reactor (NETZSCH STA2500 Regulus, weight resolution of 0.03 µg, temperature resolution of 0.3 K) equipped with a type S thermocouple (temperature resolution of ±0.0025 × |t| • C) for the TR and subsequent exothermic CS steps of the sample. The influences (general drift and amount of sample) of the thermogravimetric reactor used in this study on the redox reactivity were described and discussed in detail in our previous study [53]. The redox performance of the samples was evaluated using the following procedure: approximately 50 mg of the sample was packed into a platinum pan and placed on the balance of the reactor.…”

“…Recently, the authors reported that Ni, Co, and Mg substitutions at the B site in a series of LaSrMn-based perovskites (La 0.7 Sr 0.3 Mn 0.9 X 0.1 O 3 (X = Mg, Al, Cr, Fe, Co, Ni, Cu, and Ga)) enhanced the productivity and rate of CO production and maintained stoichiometric production (CO/O 2 = 2) with high thermal durability over 50 cycles [53]. Based on the screening test, Mg, Co, and Ni substitutions were selected in the current study to improve the O 2 and CO productivities and production behavior of the respective steps in the CO 2 thermochemical cycle using LSM perovskites by identifying the optimum chemical composition by A-and B-site substitution and to evaluate the redox performance in comparison with previous literature.…”