Nitrogen-doped graphene supported single-atom catalysts for efficient electrocatalytic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid: a density functional theory study

Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is a promising alternative for oxygen evolution reactions. The search for efficient catalysts has been attracting increasing scientific attention. This work explores the performance of nitrogen-doped graphene-supported single-atom catalysts (M-NC SACs) for the reaction. Hydroxide was found to compete with HMF for the adsorption site on early transition metal SACs. Electronic structure analysis showed that only the electron density of the functional group directly bonded to the metal site is significantly perturbed upon adsorption. Two reaction free energies were identified as descriptors for constructing the activity volcano. Scaling relation analysis elucidated the general mechanism of the reaction including the trend for the activation of the aldehyde and alcohol groups of HMF, the potential-limiting steps, and the preferred reaction pathways. In general, the reaction is limited by an aldehyde/alcohol oxidation step in the scenarios of weak/strong adsorption regardless of the reaction pathways. Nine promising candidate catalysts were proposed, including Mn, Sc, Co, Cd, Ru, Y, Cr, Fe, and Zn SACs with limiting potentials not exceeding 0.51 V. This work provides valuable insights into the electrocatalytic oxidation mechanism of HMF to FDCA on M-NC SACs and proposes candidate catalysts to guide future research.