期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 54, 期 8, 页码 2472-2476出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201409333
关键词
amorphization; cobalt oxide; cobalt phosphate; electrocatalysis; water oxidation
资金
- Deutsche Forschungsgemeinschaft (DFG) [SPP 1613 (DA 402/7-1)]
- Cluster of Excellence Unifying Concepts in Catalysis (UniCat, Berlin)
- CONICIT-MICIT (Costa Rica)
Is water oxidation catalyzed at the surface or within the bulk volume of solid oxide materials? This question is addressed for cobalt phosphate catalysts deposited on inert electrodes, namely crystallites of pakhomovskyite (Co-3(PO4)(2)8H(2)O, Pak) and phosphate-containing Co oxide (CoCat). X-ray spectroscopy reveals that oxidizing potentials transform the crystalline Pak slowly (5-8h) but completely into the amorphous CoCat. Electrochemical analysis supports high-TOF surface activity in Pak, whereas its amorphization results in dominating volume activity of the thereby formed CoCat material. In the directly electrodeposited CoCat, volume catalysis prevails, but not at very low levels of the amorphous material, implying high-TOF catalysis at surface sites. A complete picture of heterogeneous water oxidation requires insight in catalysis at the electrolyte-exposed outer surface, within a hydrated, amorphous volume phase, and modes and kinetics of restructuring upon operation.
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