Optimizing the Oxygen‐Catalytic Performance of Zn–Mn–Co Spinel by Regulating the Bond Competition at Octahedral Sites
Zepan Wang, Peiyuan Wu, Xubing Zou, Sheng Wang, Lei Du, Ting Ouyang, Zhao‐Qing Liu
Abstract
Abstract By using the more electro‐negative Mn 3+ ion to partially replace Co 3+ at the octahedral site of spinel ZnCo 2 O 4 , i.e., forming ternary Zn–Mn–Co spinel oxide, the electrocatalytic oxygen reduction/evolution activity is found to be significantly increased. Considering the physical characterization and theoretical calculations, it demonstrated that the bond competition played a key role in regulating the cobalt valence state and the electrocatalytic activity. The partial replacement of octahedral‐site‐occupied Co 3+ by Mn 3+ can effectively modulate the adjacent Co–O bond and induce the Jahn–Teller effect, thus changing the originally stable crystal structure and optimizing the binding strength between the active center and reaction intermediates. Certainly, the Mn‐substituted ZnMn 1.4 Co 0.6 O 4 /NCNTs exhibit higher electrocatalytic oxygen reduction reaction (ORR) activity than that of ZnCo 2 O 4 /NCNTs and ZnMn 2 O 4 /NCNTs, supporting that the Co–O bond covalency determines the ORR activity of spinel ZnCo 2 O 4 . This study offers the competition between adjacent Co–O and Mn–O bonds via the B Oh –O–B Oh edge‐sharing geometry. The ion substitution at octahedral sites by less electronegative cations can be a new and effective way to improve the electrocatalytic performance of cobalt‐based spinel oxides.