Hole‐Trapping‐Induced Stabilization of Ni^4 + in SrNiO₃/LaFeO₃ Superlattices

Abstract

Creating new functionality in materials containing transition metals is predicated on the ability to control the associated charge states. For a given transition metal, there is an upper limit on valence that is not exceeded under normal conditions. Here, it is demonstrated that this limit of 3+ for Ni and Fe can be exceeded via synthesis of (SrNiO3)m/(LaFeO3)n superlattices by tuning n and m. The Goldschmidt tolerance constraints are lifted, and SrNi4+O3 with holes on adjacent O anions is stabilized as a perovskite at the single‐unit‐cell level (m = 1). Holding m = 1, spectroscopy reveals that the n = 1 superlattice contains Ni3+ and Fe4+, whereas Ni4+ and Fe3+ are observed in the n = 5 superlattice. It is revealed that the B‐site cation valences can be tuned by controlling the magnitude of the FeO6 octahedral rotations, which, in turn, determine the energy balance between Ni3+/Fe4+ and Ni4+/Fe3+, thus controlling emergent electrical properties such as the band alignment and resulting hole confinement. This approach can be extended to other systems for synthesizing novel, metastable layered structures with new functionalities.

Synergetic Metal Defect and Surface Chemical Reconstruction into NiCo2S4/ZnS Heterojunction to Achieve Outstanding Oxygen Evolution Performance

“…[9] In addition, the difference in electronegativity between different sulfides is another driver of charge redistribution and band shift in such systems. [10] Therefore,c harge rearrangement in heterogeneous structure can accelerate electron transfer, stimulate the internal electric field effect, and thus enhance OER activity and reaction kinetics. [10] Thei ntroduction of appropriate defect offers another effective strategy to promote the electrocatalytic performance of metal sulfides.E lectrons in the vacancy can be excited into the conduction band, introducing an ew gap in the conduction band which is conducive to the oxygen adsorption.…”

“…[10] Therefore,c harge rearrangement in heterogeneous structure can accelerate electron transfer, stimulate the internal electric field effect, and thus enhance OER activity and reaction kinetics. [10] Thei ntroduction of appropriate defect offers another effective strategy to promote the electrocatalytic performance of metal sulfides.E lectrons in the vacancy can be excited into the conduction band, introducing an ew gap in the conduction band which is conducive to the oxygen adsorption. [11] In addition, metal defects can adjust the electronic structure of adjacent atoms,t hus altering the energy barrier of the reaction intermediate.Furthermore,the strain-induced high-energy surface structures induced by defects are more likely to resist surface reconstruction during catalysis.…”

Spontaneous phase segregation of Sr 2 NiO 3 and SrNi 2 O 3 during SrNiO 3 heteroepitaxy

“…As a result, interface engineering and limiting SNO deposition to 1 u.c. in the superlattices could generate novel ground states (such as Ni 4+ ) unobtainable in bulk crystals ( 22 ). However, once the SNO film thickness exceeds 1 u.c., the large ionic radius ratio R(Sr 2+ )/R(Ni 4+ ) and the instability of Ni 4+ could promote phase segregation.…”

Synergetic Metal Defect and Surface Chemical Reconstruction into NiCo2S4/ZnS Heterojunction to Achieve Outstanding Oxygen Evolution Performance

“…Therefore, the charge transfer energy between the 3d orbitals of different transition metals and the S 2p orbitals becomes the key parameter to determine the charge balance [9] . In addition, the difference in electronegativity between different sulfides is another driver of charge redistribution and band shift in such systems [10] . Therefore, charge rearrangement in heterogeneous structure can accelerate electron transfer, stimulate the internal electric field effect, and thus enhance OER activity and reaction kinetics [10] …”

“…In addition, the difference in electronegativity between different sulfides is another driver of charge redistribution and band shift in such systems [10] . Therefore, charge rearrangement in heterogeneous structure can accelerate electron transfer, stimulate the internal electric field effect, and thus enhance OER activity and reaction kinetics [10] …”