Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution

Abstract

Understanding the interaction between water and oxides is critical for many technological applications, including energy storage, surface wetting/self-cleaning, photocatalysis and sensors. Here, we report observations of strong structural oscillations of BaSrCoFeO (BSCF) in the presence of both HO vapour and electron irradiation using environmental transmission electron microscopy. These oscillations are related to the formation and collapse of gaseous bubbles. Electron energy-loss spectroscopy provides direct evidence of O formation in these bubbles due to the incorporation of HO into BSCF. SrCoO was found to exhibit small oscillations, while none were observed for LaSrCoO and LaCoO. The structural oscillations of BSCF can be attributed to the fact that its oxygen 2p-band centre is close to the Fermi level, which leads to a low energy penalty for oxygen vacancy formation, high ion mobility, and high water uptake. This work provides surprising insights into the interaction between water and oxides under electron-beam irradiation.

Factors Controlling the Redox Activity of Oxygen in Perovskites: From Theory to Application for Catalytic Reactions

“…From this description based on MO* states, an important addition to our understanding was made by analogy with the gas phase field for which the energy gap between the O p-band center and the Fermi level was shown to correlate with the oxygen surface exchange kinetics [9]. Going further in this direction, the demonstration was made that moving the Fermi level closer to the O p-band center of double perovskites Ln 0.5 Ba 0.5 CoO 3-δ (Ln = Pr, Sm, Gd and Ho) correlates with the OER activity as well as with the stability of the perovskites for which accessing oxygen states leads to severe surface decomposition such as for Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ perovskite or as recently demonstrated for manganites [66,[75][76][77].…”

“…If confirmed, the direct formation of an O-O bond within the structure of quadrupole perovskites would be of great interest, and would confirm measurements made on SrCoO3 showing that direct coupling of two lattice oxygen is a possible pathway for OER [6]. This approach shows promise not only in terms of activity, but also in terms of stability as it provides a unique way to nearly suppress the use of basic alkaline-earth cations that are prone to leach out in alkaline solution or in contact with water [53,77,95,96], as recently spotted by in situ TEM for Ba0.5Sr0.5Co0.8Fe0.2O3−δ [75].…”

“…Finally, the best example of cations leaching is given for vacancy-containing Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) which is thermodynamically predicted as unstable and expected to decompose at relatively low temperatures into a mixture of several cubic and hexagonal perovskite phases, [11] and further experimentally confirmed [77,96]. Eventually, Han et al directly visualized the formation of gaseous O 2 during the incorporation of H 2 O into the lattice of BSCF where dramatic structural oscillations were observed by in situ environmental transmission electron microscopy (ETEM) [75].…”

Flame‐Engraved Nickel–Iron Layered Double Hydroxide Nanosheets for Boosting Oxygen Evolution Reactivity

“…Tremendous researches have been dedicated in designing outstanding OER catalysts. Noble metals like Ir and Ru, metal oxides, perovskites, and metal hydroxides have been proved to be effective to lower the onset potential of OER. Among all, NiFe layered double hydroxide (NiFe‐LDH) has been accepted as a promising OER catalyst with large reserves and optimal activity.…”

Ultrathin Two‐Dimensional Nanostructured Materials for Highly Efficient Water Oxidation

“…For instance, Nocera's group reported that Co–phosphate and Ni–borate exhibited high activity and excellent durability to catalyze the OER under mild conditions . Shao‐Horn's group demonstrated perovskite Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3–δ as an OER catalyst with superior performance and further uncovered the interaction between perovskite oxides and water molecules . Earth‐abundant first‐row transition metal (Fe, Co, Ni, etc.…”