Surface chemistry evolution in LnBaCo2O5 +  double perovskites for oxygen electrodes

Effect of crystal orientation on the segregation of aliovalent dopants at the surface of La0.6Sr0.4CoO3

“…These are the formation of Sr-rich precipitates at the surface, as in the present study, and the formation of a thin SrO termination layer at the top surface shown by low energy ion scattering and by ICP mass spectroscopy. 17,19,24,35 As a result of this surface chemical degradation, LSC loses its reactivity to ORR typically up to two orders of magnitude in the presence of such Sr-rich precipitate formation, as shown in the literature including our own previous reports. 17,19 The apparent area coverage by such insulating precipitates is 0.1-7.0% in this work, and at the most up to 30% in our previous work studying thin lms.…”

The interaction of molecular oxygen on LaO terminated surfaces of La2NiO4

“…Only recently, it has been shown that the surfaces of perovskite and perovskite-related oxides are dominated by AO termination at SOFC cathode operating conditions. [17][18][19][20][21] The discovery represents a significant challenge for computational science which has to elucidate the chemical mechanisms that take place on that particular surface termination. 22,23 In addition, theoretical investigations suggest that relative stabilities of surfaces of perovskite related oxides are energetically equivalent for both terminations.…”

The effect of potassium on the properties of PrBa 1−x Co 2 O 5+δ (x = 0.00–0.10) cathodes for intermediate-temperature solid oxide fuel cells

“…The opposite trend was reported in the other cation deficient perovskites in the absence of K during sample synthesis [15,17,39,41]. The complex oxygen exchange process is known to be surface sensitive reactions, which are significantly influenced by the materials' surface properties, such as their compositions and morphologies [13,19]. The surface properties of the PrBa 1Àx Co 2 O 5þd (x ¼ 0.00e0.10) cathodes studied in this work were characterized by XPS to obtain the materials' chemical compositions, which are listed in Table 4.…”

“…The surface properties of the PrBa 1Àx Co 2 O 5þd (x ¼ 0.00e0.10) cathodes studied in this work were characterized by XPS to obtain the materials' chemical compositions, which are listed in Table 4. As x increased, a clear decrease in the proportion of transition metal ions (i.e., Co ions) was observed for the PrBa 1Àx Co 2 O 5þd (x ¼ 0.00e0.10) oxides, which have been reported to have inferior rates of oxygen surface exchange processes [13,19]. Therefore, the observed abnormal increase in R m with increasing x likely resulted from the decrease in the amount of Co on the surfaces of the double perovskites.…”

“…Moreover, oxygen surface exchange processes of the double perovskites are very sensitive to their surface properties [13]. Significant surface composition segregation and morphology reconstruction were observed by T ellez et al [19] and Cox-Galhotra et al [13] for PrBaCo 2 O 5þd , which may be originated from the cation size mismatch and charge interaction [22,23]. The introduction of appropriate Ba deficiencies in PrBaCo 2 O 5þd can reduce the cation size mismatch in the A site and thus tailoring the surface properties of the double perovskites.…”