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Monitoring the Hydrothermal Growth of Cobalt Spinel Water Oxidation Catalysts: From Preparative History to Catalytic Activity
Author(s) -
Reith Lukas,
Lienau Karla,
Cook Daniel S.,
Moré René,
Walton Richard I.,
Patzke Greta R.
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201801565
Subject(s) - catalysis , hydrothermal circulation , cobalt , powder diffraction , cobalt oxide , spinel , materials science , hydrothermal synthesis , chemical engineering , quenching (fluorescence) , amorphous solid , inorganic chemistry , chemistry , crystallography , metallurgy , organic chemistry , physics , quantum mechanics , engineering , fluorescence
The hydrothermal growth of cobalt oxide spinel (Co 3 O 4 ) nanocrystals from cobalt acetate precursors was monitored with in situ powder X‐ray diffraction (PXRD) in combination with ex situ electron microscopy and vibrational spectroscopy. Kinetic data from in situ PXRD monitoring were analyzed using Sharp–Hancock and Gualtieri approaches, which both clearly indicate a change of the growth mechanism for reaction temperatures above 185 °C. This mechanistic transition goes hand in hand with morphology changes that notably influence the photocatalytic oxygen evolution activity. Complementary quenching investigations of conventional hydrothermal Co 3 O 4 growth demonstrate that these insights derived from in situ PXRD data provide valuable synthetic guidelines for water oxidation catalyst production. Furthermore, the ex situ analyses of hydrothermal quenching experiments were essential to assess the influence of amorphous cobalt‐containing phases arising from the acetate precursor on the catalytic activity. Thereby, the efficient combination of a single in situ technique with ex situ analyses paves the way to optimize parameter‐sensitive hydrothermal production processes of key energy materials.