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Nature Physics, Published online: 06 November 2023; doi:10.1038/s41567-023-02266-2

Interactions between excitons and correlated electrons can lead to the formation of interesting states. Now, evidence suggests that these interactions can give rise to a Mott insulator of excitons.

The electrooxidation of 5-hydroxymethylfurfural (HMFOR) process is complicated, including the HMF and OH⁻ jointly adsorbed and coupled with each other. In this work, the role of oxygen vacancies is investigated during HMFOR. It is found that the OH⁻ tends to fill into Vo and participate in the dehydrogenation of HMF molecules, which can improve the catalytic activity of HMFOR.

Abstract

The electrooxidation of 5-hydroxymethylfurfural (HMF) offers a promising green route to attain high-value chemicals from biomass. The HMF electrooxidation reaction (HMFOR) is a complicated process involving the combined adsorption and coupling of organic molecules and OH⁻ on the electrode surface. An in-depth understanding of these adsorption sites and reaction processes on electrocatalysts is fundamentally important. Herein, the adsorption behavior of HMF and OH⁻, and the role of oxygen vacancy on Co₃O₄ are initially unraveled. Correspondingly, instead of the competitive adsorption of OH⁻ and HMF on the metal sites, it is observed that the OH⁻ can fill into oxygen vacancy (Vo) prior to couple with organic molecules through lattice oxygen oxidation reaction process, which could accelerate the rate-determining step of the dehydrogenation of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) intermediates. With the modulated adsorption sites, the as-designed Vo-Co₃O₄ shows excellent activity for HMFOR with the earlier potential of 90 and 120 mV at 10 mA cm⁻² in 1 m KOH and 1 m PBS solution. This work sheds insight on the catalytic mechanism of oxygen vacancy, which benefits designing a novel electrocatalysts to modulate the multi-molecules combined adsorption behaviors.