Crystal structure and surface characteristics of Sr-doped GdBaCo₂O_6−δ double perovskites: oxygen evolution reaction and conductivity

Abstract

Upon Sr-doping in GdBa1−xSrxCo2O6−δ, a shift of the valence band maximum VBmax towards the Fermi energy EF was observed leading to better OER activity.

Synergistic Interaction of Double/Simple Perovskite Heterostructure for Efficient Hydrogen Evolution Reaction at High Current Density

“…The dominant binding energies with peak maxima at ≈90.7 and ≈88.2 eV correspond to the Ba‐O environments in the perovskites. [ 27 ] Figure 3h shows the Co 2p/Ba 3d profiles of PBC, PB 0.94 C, and PB 0.94 C‐DSPH. Although the overlap between Co 2p and Ba 3d main peaks makes it difficult to accurately identify the surface Co valence, as the chemical shift between Co 2p/Ba 3d is only around 0.3–0.4 eV, two strong lines locating at ≈779.5 and ≈795 eV indicate that the main oxidation state of Co ions in the perovskite samples is 3+.…”

“…Although the overlap between Co 2p and Ba 3d main peaks makes it difficult to accurately identify the surface Co valence, as the chemical shift between Co 2p/Ba 3d is only around 0.3–0.4 eV, two strong lines locating at ≈779.5 and ≈795 eV indicate that the main oxidation state of Co ions in the perovskite samples is 3+. [ 27a,28 ] The apparent shoulder peaks at 777.4 and 792.6 eV in PBC and PB 0.94 C are ascribed to the Ba–O interrelation, evidence for the structural stress from oxygen nonstoichiometry and A‐site deficiency. [ 9,29 ] The intensity of interrelation peaks becomes weaker for PB 0.94 C‐DSPH after the separation of simple perovskite because double/simple perovskite phases revert to more stable structures.…”

Systematic Study of Descriptors for Oxygen Evolution Reaction Catalysis in Perovskite Oxides

“…A volcano-type plot along the e g electron number was originally proposed by Suntivich et al, 17 and is widely accepted at present. 21,22,[39][40][41][42][43][44][45][46][47][48] Figure 4a shows η versus e g electron number for the perovskite oxides, where the e g electron numbers were estimated from the most likely electron configurations (Table S3) Indeed, these average values apparently followed a gradient volcano-like shape (dashed curve in Figure 4a). However, compared with the previous report, 17 it does not efficiently serve to describe OER activity because of wide dispersion of data points (see error bars in Figure 4a).…”

Recent Advances of Cobalt-Based Electrocatalysts for Oxygen Electrode Reactions and Hydrogen Evolution Reaction

“…The diagram in Figure 12 displays two different routes to form oxygen from a MO intermediate. One, the green route, via the direct combination of 2MO to produce O 2(g) (Equation (11)), and that involving the generation of the MOOH intermediate (Equations (12) and (17)) which subsequently decomposes, black route, to O 2(g) (Equations (13) and (18) Until now, the Ni-and Co-based materials (both free support and supported on, e.g., carbon) have been intensively investigated as promising non-precious OER electrocatalysts. The catalysts derived from cobalt metal centers can activate the OER in alkaline medium rather than in acid medium.…”

“…Therefore, it is of increasing interest to reduce the usage of precious metals, or completely replace precious metals with abundant, cheap and highly active ones. In the past few years, various kinds of novel non-precious metal nanomaterials have been explored as alternatives to precious metal-based electrocatalysts, including strongly coupled transition metals (oxides, phosphides, chalcogenides, hydroxides, double perovskites, and so on) [8][9][10][11][12][13][14], nanocarbon hybrids [15], and free-metal carbonbased materials [7,16].…”