Constructing Oxygen Vacancy‐Enriched Ag‐Mn(OH) ₂ via Anionic Leaching and Ag Modification: Inducing High‐Valence Mn Active Sites for Efficient Electrocatalytic Oxidation of 5‐Hydroxymethylfurfural

Abstract Electrochemical oxidation of 5‐hydroxymethylfurfural (HMF) using non‐precious transition metal catalysts presents a sustainable pathway for producing high‐value 2,5‐furandicarboxylic acid (FDCA). Manganese‐based materials hold promise for HMF oxidation reactions but suffer from low intrinsic conductivity and sluggish kinetics in the formation of high‐valence Mn active species. Herein, a multi‐scale engineering strategy to construct a 3D Ag‐Mn(OH) ₂ ‐O _V /nickel foam (NF) catalyst by synergistically integrating electrochemical activation‐induced MoO ₄ ²⁻ leaching and Ag nanoparticle modification on a pre‐synthesized MnMoO ₄ /NF is proposed. Spectroscopic characterizations reveal that this dual‐functional modification strategy collectively generates an Ag‐Mn(OH) ₂ ‐O _V /NF heterostructure enriched with oxygen vacancies (O _V ), thereby facilitating the formation of high‐valent Mn ³⁺ active centers. Moreover, the synergistic interplay between O _V and Ag nanoparticles not only enhances the adsorption of reactants and reaction intermediates but also optimizes interfacial charge transfer, consequently lowering the overall reaction energy barrier. These cooperative effects collectively drive the superior catalytic performance of the Ag‐Mn(OH) ₂ ‐O _V /NF. As a result, the Ag‐Mn(OH) ₂ ‐O _V /NF catalyst achieves 100% HMF conversion rate and 98.60% FDCA Faradaic efficiency (FE) at 1.40 V versus. RHE, with its FE significantly higher than those of catalysts Mn(OH) ₂ ‐O _V /NF (70.11%) and Ag/NF (62.02%), and the electrolysis time is approximately halved.