Tuning the geometric and electronic structure of the single-metal-atom catalysts via simultaneous presence of metal nanoparticles or nanoclusters (NCs) offers an alternative avenue to improving their catalytic performance. Herein, we demonstrate that the coexistence of Fe NCs in proximity to Fe single atoms on N-doped porous carbon can significantly improve the catalytic performance in aerobic oxidation of primary amines to imines using air as the oxidant. A broad spectrum of primary aromatic, heterocyclic, and aliphatic amines was efficiently and selectively oxidized into their corresponding imines in good to high yields. Experimental measurements and theoretical calculations reveal that the proximity of Fe NCs interacts with Fe single atoms, which not only benefits the adsorption of molecular O2 and amine substrates but also promotes the activation of O2 to selectively generate singlet oxygen (1O2) and then facilitates the key intermediate imine formation via H-atom abstraction with a lower energy barrier, thereby significantly boosting the reaction activity.

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Degradation of 29 dyes by means of an activated carbon fiber (ACF) electrode electrolysis system was performed successfully. Almost all dye solutions tested were decolorized effectively in this ACF electrolysis process. Internal relationships between treatment mechanisms and chemical composition of the dye have been discussed in this paper. Generally, it is shown that higher solubility leads to greater degradation in the process. Dyes with many -SO 3 − , COO − , -SO 2 NH 2 , -OH, hydrophilic groups, and azo linkages are susceptible to reduction. However, dyes with many -C=O, -NH-and aromatic groups, and hydrophobic groups, tend to be adsorbed. For dyes with -SO 3 − , -COOH and -OH groups, if their molecules linearly spread in solution and have a significant tendency to form colloids by hydrogenous bonding, they also tend to be adsorbed and flocculated. Typical dynamic electrolysis of dye Acid Red B, Vat Blue BO and Disperse Red E-4B shows how the two major mechanisms, degradation and adsorption, act differently during treatment. Reduction occurs evenly during treatment. During the dominant adsorption process, after certain amount of iron is generated, colloid precipitation occurs and TOC and color are rapidly removed.