Jahn-Teller distortion lowers the kinetic barrier for Co3+/Co4+ redox: A pathway to ultrafast HMF electrooxidation

Mn incorporation into Co 3 O 4 induces Jahn–Teller distortion and Co 3+ spin-state transition ( t 2 g 6 e g 0  →  t 2 g 5 e g 1 ). • Such electronic modulation weakens Co O bonding and lowers Co 3+  → Co 4+ kinetic barrier. • Mn-Co 3 O 4 achieves ∼100% HMF conversion, 97.8% FDCA yield, and 96.0% Faradaic efficiency at 1.4 V vs. RHE. • DFT reveals that Mn incorporation reduces the PDS free energy from 4.05 eV to 2.11 eV by facilitating α-C–H cleavage. The electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is a key transformation for sustainable polymer production, yet its efficiency is hampered by the kinetically demanding cleavage of the α-C–H bonding in the hydroxymethyl group. Herein, we demonstrate that Jahn–Teller distortion serves as an effective strategy to overcome this limitation. By incorporating Mn 3+ ( t 2g 3 e g 1 ) into Co 3 O 4 , we induce a spin-state transition of Co 3+ from low-spin ( t 2g 6 e g 0 ) to intermediate-spin ( t 2g 5 e g 1 ), which weakens Co O bonding and lowers the kinetic barrier for Co 3+  → Co 4+ oxidation. Compared with that of Co 3 O 4 , Mn-Co 3 O 4 achieves a complete HMF conversion with 97.8% of FDCA yield and 96.0% of Faradaic efficiency at 1.4 V vs. RHE, representing a 3.72-fold enhancement in intrinsic activity. Computational and theoretical analysis corroborates that Mn-induced Jahn–Teller electronic modulation not only benefits the adsorption and activation of HMF molecules but also facilitates the cleavage of α-C–H bonding, thereby lowering the reaction barrier. This work establishes Jahn–Teller-distortion-mediated Co 3+ /Co 4+ redox regulation as a focused electronic-structure strategy for promoting high-valence-Co-driven HMF electrooxidation. The Jahn-Teller-driven generation of high-valence Co 4+ species in pristine Co 3 O 4 by the incorporation of Mn 3+ ( t 2g 3 e g 1 ) accelerate the rate-determining initial oxidation of hydroxymethyl groups, markedly enhancing reaction kinetics of HMF to FDCA. Download: Download high-res image (150KB) Download: Download full-size image