Beschreibung:
<jats:title>Abstract</jats:title><jats:p>By using the crystalline precursor decomposition approach and direct co‐precipitation the composition and mesostructure of cobalt‐based spinels can be controlled. A systematic substitution of cobalt with redox‐active iron and redox‐inactive magnesium and aluminum in a cobalt spinel with anisotropic particle morphology with a preferred 111 surface termination is presented, resulting in a substitution series including Co<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub>, MgCo<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub>, Co<jats:sub>2</jats:sub>FeO<jats:sub>4</jats:sub>, Co<jats:sub>2</jats:sub>AlO<jats:sub>4</jats:sub> and CoFe<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub>. The role of redox pairs in the spinels is investigated in chemical water oxidation by using ceric ammonium nitrate (CAN test), electrochemical oxygen evolution reaction (OER) and H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> decomposition. Studying the effect of dominant surface termination, isotropic Co<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> and CoFe<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> catalysts with more or less spherical particles are compared to their anisotropic analogues. For CAN‐test and OER, Co<jats:sup>3+</jats:sup> plays the major role for high activity. In H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> decomposition, Co<jats:sup>2+</jats:sup> reveals itself to be of major importance. Redox active cations in the structure enhance the catalytic activity in all reactions. A benefit of a predominant 111 surface termination depends on the cobalt oxidation state in the as‐prepared catalysts and the investigated reaction.</jats:p>