Manganese Doping in Cobalt Oxide Nanorods Promotes Catalytic Dehydrogenation

Abstract

Heteroatom doping in nanomaterials can import new active sites and promote catalytic activity. Here we report that Mn-doped Co3O4 nanorods (Mnx-Co3O4) via substituting Mn3+ (t2g3-eg1) for Co3+ (t2g6-eg0) exhibit ∼100% yield for 4-methyl benzyl alcohol dehydrogenation catalysis at 60 °C and no decay (8 cycles), compared with only 1.4% of activity for bare Co3O4 catalysts. We characterize the fine structures of Mnx-Co3O4 at the atomic level and demonstrate that the superior catalytic performance is strongly related to the Mn3+-induced Jahn–Teller (J–T) effect, which is a geometric distortion that has generally been considered to be disadvantageous for applications. Experimental observations and theoretical calculations reveal that unsaturated Mn3+ with J–T distortion acts as an active site, and readily reacts with −OH groups of benzyl alcohol adsorbed nearby, simultaneously promoting dehydrogenation to directly yield benzaldehyde. Mnx-Co3O4 catalysts rapidly dehydrogenate alcohols into aldehydes/ketones for 19 reactions with >99.9% selectivity and 14 examples with >90.2% yield.