Cobalt Nanoparticles Encapsulated in Nitrogen-Doped Carbon Nanotubes for Highly Efficient Electrochemical Oxidation of 5-Hydroxymethylfurfural Coupled with 4-Nitrophenol Hydrogenation

The electrocatalytic conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) holds significant research value and broad application potential. The catalyst, comprising cobalt nanoparticles (Co NPs) encapsulated within nitrogen-doped carbon nanotubes (NCNTs) grown in situ on carbon paper (Co@NCNT/CP), was successfully developed. The catalyst achieved paired electrocatalytic reactions for HMF oxidation coupled with 4-nitrophenol (4-NP) reduction. Both HMF and 4-NP exhibited conversion rates exceeding 99%. The FDCA yield and selectivity reached 97%, with a Faradaic efficiency of 99%. The 4-aminophenol (4-AP) yield and Faradaic efficiency were 98%. Mechanistic studies revealed that electrochemically generated Co3+ species serve as the primary active sites for HMF oxidation. Electron interactions between the NCNTs and encapsulated Co NPs further stabilize the cobalt valence state. The structure facilitates HMF adsorption on Co NP surfaces, primarily via the Eley–Rideal mechanism, promoting catalytic conversion under high HMF concentrations. The paired electrochemical system exhibited outstanding catalytic performance and faster reaction rates for synergistic HMF oxidation and 4-NP hydrogenation than for individual reactions.