H₂O₂‑Driven Structural and Electronic Modulation of NiMn Electrocatalysts for Enhanced Electrooxidation of HMF to DFF

2,5-Diformylfuran (DFF) is an important oxidation product of 5-hydroxymethylfurfural (HMF) with significant industrial relevance; however, achieving high selectivity using non-noble metal electrocatalysts remains challenging. Herein, hydrogen peroxide (H₂O₂) was introduced during the electrodeposition of NiMn-C to induce in situ oxidative reconstruction. This treatment induces morphological roughening, generates oxygen vacancies, and alters the Mn oxidation state, collectively modifying the structural and electronic properties of the catalyst. The resulting materials were characterized by FTIR, XRD, FE-SEM, and XPS and subsequently evaluated for HMF electrooxidation. The H₂O₂-treated NiMn-C catalyst exhibits enhanced activity and maintains high DFF selectivity (90.7%) at 1.65 V vs RHE, producing nearly twice the DFF yield compared to the untreated NiMn-F sample. These findings demonstrate that oxidative-agent-driven structural and electronic modulation provides an effective strategy for improving the performance of non-noble metal electrocatalysts for biomass oxidation.