Interfacial Engineering in Ag ₂ S‐bridged Ni ₃ S ₂ /Ag ₂ S‐Ag Heterostructure for Promoting 5‐Hydroxymethylfurfural Electrooxidation

ABSTRACT The electrochemical oxidation of 5‐hydroxymethylfurfural (HMF) to high‐valued 2,5‐furandicarboxylic acid (FDCA) represents a sustainable route to petroleum‐derived monomers, yet optimized adsorption and interface‐regulated indirect oxidation to promote HMF oxidation reaction (HMFOR) remains a critical challenge. A unique Ag 2 S interfacial structure finely tuning Ag and Ni 3 S 2 surface (named Ni 3 S 2 /Ag 2 S‐Ag) is successfully fabricated at the metal‐support junction. The unique Ag 2 S interfacial layer serves as an electronic bridge to facilitate directional electron transfer from Ni 3 S 2 to metallic Ag, thus promoting the activation of Ni sites. The dynamic Ni 2+ /Ni 3+ driven HMFOR in Ni 3 S 2 /Ag 2 S‐Ag (indirect oxidation), leading to an industrial‐grade current density (549.7 mA·cm −2 ) and high FEs (FE HMFOR of 90.2% and FE 4‐NPRR of 83.5% within 266 h regeneration) in the coupled HMFOR and 4‐nitrophenol reduction reaction (4‐NPRR) system. Techno‐economic analysis reveals a net profit of $2,637/ton HMF converted, with the strong feasibility for large‐scale application. In situ Raman spectroscopy confirms the valence‐state‐mediated indirect oxidation mechanism. Density functional theory calculations and transient electrochemical analysis demonstrate that the metal phase (Ag) significantly optimizes the substrate adsorption. Furthermore, the deactivation reasons and the regeneration methods for Ni 3 S 2 /Ag 2 S‐Ag have been explored. The regenerated bifunctional catalyst developed in this study provides a feasible strategy for the large‐scale sustainable production of high‐value‐added chemicals.