Zur Phase CoOOH

Abstract

Mit 4 Abbildungen Inhaltsubersicht ,411s Kobalt(II1)-hydroxid-Fallprodukten wurde durch Altern bei Temperaturen zwischen 120 und 300 "C unter Wasser in einem DruckgefaD die Verbindung CoOOH formel-und phasenrein hergestellt und analytisch, rontgenographisch sowie thermoanalytisch belegt. Der Ubergang von Kobalt(II1)-hydroxid zu CoOOH beruht auf einer Verbesserung des Kristallisationsgrades unter Beibehaltung des Strukturtyps verbunden mit einer Wasserabspaltung. Kobalt(II1)-hydroxid besteht somit a m sehr kleinen, gittergestorten und wasserhaltigen Teilchen von CoOOH-Struktur, fur welche die Formelschreibweise COOOH(H,O),,,~~, vorgeschlagen wird. SummaryThe compound CoOOH was prepared by aging of cobalt(II1) hydroxide precipitates between 120 and 300°C under water in a pressure vessel, and characterised analytically. thermoanalytically and by X-ray methods. The conversion of cobalt(II1) hydroxide t o CoOOH is due to an improvement of the lattice order by maintaining the basic crystal structure and is accompanied by secession of water. Cobalt(II1) hydroxide consists of very small, water containing and lattice distorted particles with CoOOH structure. Therefore, we propose its formula as COOOH(H,O),,~,~.

Core‐shell Co3O4@CoO Nanoparticles for Enhanced OER Activity

“…The Co(OH) 2 is then converted to CoO(OH) under electrochemical conditions, [80] and finally converted to the spinel-type Co 3 O 4 (Scheme 2). [81] PXRD studies on the electrochemically treated CoO nanoparticles (1) also reveal the partial transformation of rock-salt CoO into spinel-type Co 3 O 4 under anodic potentials, as evidenced by to the appearance of the characteristic (311) reflection at 36.7°(Figure 8a). In addition, the formation of Co 3 O 4 is also demonstrated by IR spectroscopy, as the tetrahedral CoÀ O vibration appears in sample 1 after chronopotentiometric measurement at 560 cm À 1 (Figure 8b).…”

“…The Co(OH) 2 is then converted to CoO(OH) under electrochemical conditions, [80] and finally converted to the spinel‐type Co 3 O 4 (Scheme 2). [81] …”

Variability of composition and structural disorder of nanocrystalline CoOOH materials

“…3,[14][15][16] There are also studies addressing the structural disorder: Petzold et al, e.g., reported on very small particles with a CoOOH-related structure that contain additional water molecules and exhibit noticeable lattice distortion. 17 Later on, Penn et al investigated the faulting-induced broadening and shifting of reflections of the (10l) zone associated with the use of specific oxidising agents. 18,19 In the present study, we investigated the impact of the synthesis route to nc CoOOH on the relevant characteristics of the heterogenite materials by using three different preparation approaches.…”