Low-Temperature Solvothermal Approach to the Synthesis of La₄Ni₃O₈ by Topotactic Oxygen Deintercalation

Abstract

A chimie douce solvothermal reduction method is proposed for topotactic oxygen deintercalation of complex metal oxides. Four different reduction techniques were employed to qualitatively identify the relative reduction activity of each including reduction with H(2) and NaH, solution-based reduction using metal hydrides at ambient pressure, and reduction under solvothermal conditions. The reduction of the Ruddlesden-Popper nickelate La(4)Ni(3)O(10) was used as a test case to prove the validity of the method. The completely reduced phase La(4)Ni(3)O(8) was produced via the solvothermal technique at 150 °C--a lower temperature than by other more conventional solid state oxygen deintercalation methods.

The First Observation of Metallic Behaviour in Nd3.5Sm0.5Ni3O8

“…Comparing to Nd 3.5 Sm 0.5 Ni 3 O 8 before sulfur-intercalation, -axis shrinks at 1.5% and -axis expands at 6.4%. There exists La 4 Ni 3 O 9 and this material can be regarded as the compound that an oxygen atom is intercalated in-between sites of NiO 2 layer of La 4 Ni 3 O 8 having the identical structure to Nd 3.5 Sm 0.5 Ni 3 O 8 [15,16]. By this oxygen-intercalation for La 4 Ni 3 O 8 , -axis is shrunk at 2% and -axis is expanded at 5% [15,16].…”

“…There exists La 4 Ni 3 O 9 and this material can be regarded as the compound that an oxygen atom is intercalated in-between sites of NiO 2 layer of La 4 Ni 3 O 8 having the identical structure to Nd 3.5 Sm 0.5 Ni 3 O 8 [15,16]. By this oxygen-intercalation for La 4 Ni 3 O 8 , -axis is shrunk at 2% and -axis is expanded at 5% [15,16]. The variation of lattice constants of oxygen-intercalation has the very similar tendency with the case of sulfur-intercalation for Nd 3.5 Sm 0.5 Ni 3 O 8 .…”

Enhanced CO catalytic oxidation by Sr reconstruction on the surface of La x Sr 1− x CoO 3− δ

“…In this work, we take a novel approach to precisely control the sample surface with dilute KBH 4 solution and realize the engineering of several atomic layers on the surface, which can create more surface oxygen vacancies. In previous studies, alkali metal borohydrides are frequently used to prepare noble metal, alloy and reduced metal oxides [36]. However, in this work, high-activity hydrogen atom in KBH 4 is used to react with the surface oxygen atom of SrCoO 3Àd layer (Sr enrichment region) due to its strong reducibility.…”

Hydride Reductions of Transition Metal Oxides

“…(Figures 1c and 1d). 10,18 Unlike LaNi I O 2 , La 3 Ni 2 O 6 and La 4 Ni 3 O 8 possess a mixed-valent state of Ni(I/II), though superconductivity is absent. Interestingly, upon hydride reduction, only bridging apical oxygen atoms are deintercalated and nonbridging apical oxygen atoms are shifted away from the original position, leading to formation of fluorite type LaO layers.…”