Influence of transition metal electronegativity on the oxygen storage capacity of perovskite oxides

Abstract

The selection of highly efficient oxygen carriers (OCs) is a key step necessary for the practical development of chemical looping combustion (CLC). In this study, a series of ABO3 perovskites, where A = La, Ba, Sr, Ca and B = Cr, Mn, Fe, Co, Ni, Cu, are synthesized and tested in a fixed bed reactor for reactivity and stability as OCs with CH4 as the fuel. We find that the electronegativity of the transition metal on the B-site (λB), is a convenient descriptor for oxygen storage capacity (OSC) of our perovskite samples. By plotting OSC for total methane oxidation against λB, we observe an inverted volcano plot relationship. These results could provide useful guidelines for perovskite OC design and their other energy related applications.

Performance and Stability of Metal (Co, Mn, Cu)-Promoted La2O2SO4 Oxygen Carrier for Chemical Looping Combustion of Methane

“…La2O2SO4 + CH4 → La2O3 + SO2 + 2 H2 + CO (6) However, the formation of CO (m/z = 28) cannot be easily detected because of the use of N2 as the carrier gas. Due to the formation of some La2O3, the OC material cannot fully recover its original weight during the fast oxidation occurring as soon as it is exposed to air flow.…”

“…Large oxygen storage capacity (OSC), fast oxidation and reduction kinetics and high stability of the oxygen carrier (OC) are crucial parameters for process development [4]. A large variety of OCs have been proposed, most of them based on transition metals (Cu, Ni, Fe, Mn, Co) as bulk or supported simple oxides or as more complex oxides such as perovskite-like materials [3,5,6]. Perovskites show a better thermal stability and adjustable properties related to the partial or total substitution of A and B metal cations in their ABO 3 structure [6].…”

Liquid-Phase Exfoliation of Biochars in Green Solvents and Correlation with Solvent Parameters

“…43 In the current study, natural and exfoliated hardwood biochar samples present a higher IG/ID ratio when compared to the softwood analogues, meaning an increased sp 2 carbon content and improved crystallinity ( Table 1). Because graphitic structures are more ordered, dense, and rigid than the amorphous phase, they are less susceptible to exfoliation, 28,29 which explains the increased yields of exfoliated softwood biochar in all the solvents studied for LPE and the difficult in finding high-performance solvents for the processing of the more highly crystalline materials. Although density filters were used during Raman analysis to decrease the laser power and avoid potential thermal degradation of samples, the spectra of oxidized biochars before and after exfoliation could not be obtained.…”

“…60 h) to yield nanosheets from layered materials. 18,27 With respect to biochar, exfoliation has been achieved using LPE, [28][29][30] as well as mechanochemical techniques 31,32 and chemical pre-treatment of biomass. 33,34 So far, the identification of high-performance solvents for LPE of biochar has not been studied.…”

“…Therefore, only preliminary assessments regarding the solvent parameters and their influence on the exfoliation of biochar have been made, and biochar samples have typically been exfoliated in a reproductive toxicant solvent (N-methyl-2-pyrrolidone) or with very low yields in water. [28][29][30] An increased knowledge of the effects that the solvent properties and the nature of the biomass feedstock have on the efficiency of exfoliation can further improve our understanding of biochar's structure, promote the study of new sustainable and effective alternative solvents for LPE, and improve biochar applications as an environmentally benign advanced material. Therefore, we decided to pursue an in-depth investigation of biochar exfoliation, and identify green, benign, and high-performance solvents for the liquid-phase processing of this carbon material.…”