Synergistic Mott-Schottky and plasmonic effects promote reactive oxygen species production and reactant adsorption for efficient 5-hydroxymethylfurfural upgrading

The reactant-adsorption mechanism and reactive oxygen species (ROS) oxidation mechanism represent two vital strategies for boosting the selectivity of the 5-hydroxymethylfurfural oxidation reaction (HMFOR). Still, their compatibility remains challenging and has rarely been reported. Herein, using Pd nanoparticles as the reactant adsorption center and ROS producer, and NiMoO 4 nanorod array as the electrocatalytically active component, a Pd/NiMoO 4 Mott-Schottky heterojunction on Ni-foam skeleton is constructed. The Mott-Schottky structure tailors the Fermi level and energy band structure of Pd/NiMoO 4 , thereby reinforcing its plasmon effect. The prominent plasmon effect increases the carrier density (from 0.6 × 10 27 to 2.4 × 10 27 cm −3 ), lowers the activation energy of HMFOR (from 11.7 to 5.8 kJ mol −1 ), and triggers the formation of ROS ( 1 O 2 and ·O 2 − ) that directly attack HMF, accelerating its conversion to FDCA. Meanwhile, in situ Fourier transform infrared and Raman spectroscopy tests reveal that the decorated Pd nanoparticles not only effectively accelerate the adsorption of HMF and OH − reactants, but also promote the formation of NiOOH active sites. Under the joint effect of these favorable factors, the Pd/NiMoO 4 /NF requires only 1.32 V to afford 50 mA cm −2 under 561 nm illumination, and importantly, achieves a high HMF conversion rate of 99.3%, FDCA selectivity of 98.2%, and Faradaic efficiency of 95.2%, which are superior to those without light irradiation (98.5% HMF conversion rate, 88.7% FDCA selectivity, and 85.0% Faradaic efficiency). When assembled as an HMF-assisted anion exchange membrane HER||HMFOR electrolyzer, a voltage of merely 1.63 V is needed to deliver 500 mA cm −2 , demonstrating its vast production capacity. This multiscale regulation merges the reactant adsorption mechanism with plasmon-induced ROS, enabling the synergistic use of renewable electricity and light energy, and delivering exceptional light-assisted electrocatalytic HMF-to-FDCA performance.