Interaction of La₂NiO₄ (100) Surface with Oxygen Molecule: A First-Principles Study

Abstract

Along the way to designing of new cathode materials for solid oxide fuel cells (SOFCs), an understanding of the mechanism of oxygen reduction reaction (ORR) plays a key role, especially the interaction between O 2 molecule and surface of cathode. Recently, La 2 NiO 4 with K 2 NiF 4 -type structure has been developed, and it has received great attention as an oxygen sensor and a potential cathode for SOFCs. However, the chemical activity of La 2 NiO 4 , in particular, the ORR on the surface, has not been studied so thoroughly. In this report, we present the structural and energetic results of O 2 adsorbed onto the perfect and defective La 2 NiO 4 (100) surface to elucidate the interaction mechanism between O 2 molecule and cathode using atomistic computer simulation based on density functional theory. The results show that the surface structure and the adsorbed configurations are vital for O 2 adsorption. and activation. The adsorbed species on the perfect surface are energetically less favorable than defective surface. The Ni site is preferred with adsorption energy of −1.25 (Ni-super) and −1.80 eV (Ni-per), much higher than these of La site, supporting the fact that transition-metal cations are more active than lanthanon metals in K 2 NiF 4 -type compounds. Surface oxygen vacancy is found to enhance the adsorption energy of O 2 molecule on the La 2 NiO 4 (100) surface; in addition, oxygen vacancy can be an active site in O 2 adsorption. The most stable configuration is Ni−O−Ni mode, with the highest adsorption energy being −2.61 eV. This can be confirmed by the analysis of the local density of states (LDOS) and the difference electron density. These results have an important implication for understanding the ORR on La 2 NiO 4 (100) surface.

Segregated Chemistry and Structure on (001) and (100) Surfaces of (La1–xSrx)2CoO4 Override the Crystal Anisotropy in Oxygen Exchange Kinetics

“…This is also consistent with the presence of more Co detected by LEIS at the outermost surface of LSC25 films compared to that on LSC50 for both the (100) and (001) orientations (see Figure 5 bar charts). Given the importance of the transition metal cations for oxygen reduction at oxide surfaces [49][50][51] , this difference can be critical in determining the relative oxygen exchange kinetics at the LSC25 and LSC50 surfaces, and will be discussed further in section 3.4. Figure 7 with the HAADF-STEM image (and also with Figure 2) reveals that most of film exhibits the 214 R-P structures.…”

“…and49 , the authors also showed that defective surfaces are more reactive and that the oxygen vacancies should be involved with the adsorption and reduction of oxygen molecules at the surface. While in La 2 NiO 4+δ 49 the authors did not give any indication in the…”

The interaction of molecular oxygen on LaO terminated surfaces of La2NiO4

“…22,23 In addition, theoretical investigations suggest that relative stabilities of surfaces of perovskite related oxides are energetically equivalent for both terminations. 24,25 In an earlier investigation employing first principle techniques, the interaction of an oxygen molecule with La2NiO4 surfaces was reported by Zhou et al 26 In their work, the mechanisms of Recently, we used the DFT approach to investigate the oxygen reduction reaction on the SrOterminated surfaces of SrTiO3 and SrTi0.75Fe0.25O3-δ. 27 Experimental observations made by Low Energy Ion Scattering (LEIS) spectroscopy measurements, which can determine the elemental composition of the outermost layer 28 , identified the stable surfaces of these materials at elevated temperatures as predominantly SrO terminated.…”

Evaluation of LaxSr2−xFeO4 layered perovskite as potential electrode materials for symmetrical solid oxide fuel cells

“…Most of the compounds with K 2 NiF 4 structure have the ability to accommodate large amount of M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 interstitial oxygen ions or generate loss of oxygen vacancies. These advantages make Ln 2 MO 4 as good candidates as cathodes for SOFCs [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. However, only La 0.6 Sr 1.4 MnO 4 was reported to be a promise anode for SOFCs [28] and potential symmetrical electrode for SSOFCs [29] which showed a maximum power density of 59 mW cm -2 at 800 0 C (H 2 as a fuel).…”