Amino-Functionalized Iron-Based Metal-Organic Frameworks Anchored on Aminated Carbon Nanotubes for Selective Two-Electron Oxygen Reduction Reaction toward Efficient H2O2 Electrosynthesis.

The electrosynthesis of hydrogen peroxide (H2O2) via two-electron oxygen reduction reaction (2e- ORR) is a promising method with the advantages of safety, efficiency, and sustainability. However, the process is constrained by the low selectivity and catalytic activity of the catalysts. In this study, the amino-functionalized iron-based metal-organic frameworks anchored on aminated carbon nanotubes (Fe-BDC@CNT-NH2) are prepared as 2e- ORR catalysts to enhance H2O2 production. In this catalyst system: (1) carbon nanotubes (CNTs) were designed to improve the overall electron conductivity of the catalyst; (2) -NH2 groups in benzene-1,4-dicarboxylic acid (BDC) could modulate the intrinsic electron conductivity of metal-organic frameworks (MOFs); and (3) -NH2 groups on the CNT surface facilitated the anchoring and confinement of MOF growth by forming axial coordination structures (Fe-NO4). Smaller particles expose more active sites, while axial coordination structure enhances the adsorption capacity of Fe centers, effectively passivating Fe centers and optimizing the 2e- ORR performance at adjacent C sites. Thus, Fe-BDC@CNT-NH2 possesses high 2e- ORR selectivity and activity, under both alkaline and neutral conditions. For example, Fe-BDC@CNT-NH2 demonstrates a H2O2 average yield of 24 mol gcat-1 h-1 and maintains a Faraday efficiency (FE) > 80% over 12 h in alkaline. Against neutral conditions, it also exhibits approximately 84% selectivity and stability lasting up to 12 h. Especially, a large current of 1.0 A can be achieved under a 5 × 5 cm2 flow cell, thus endowing the electro-synthesized H2O2 with excellent dye degradation performance and broad application prospects.