Antibiotic pollution in aqueous solutions seriously endangers the natural environment and public health. In this work, Mo-doped transition metal FeCo–Se metal aerogels (MAs) were investigated as bifunctional catalysts for the removal of sulfamethazine (SMT) in solution. The optimal Mo_0.3Fe₁Co₃–Se catalyst can remove 97.7% of SMT within 60 min (SMT content: 10 mg/L, current intensity: 10 mA/cm²). The unique porous cross-linked structure of aerogel confered the catalyst sufficient active sites and efficient mass transfer channels. For the anode, Mo_0.3Fe₁Co₃–Se MAs exhibits superior oxygen evolution reaction (OER) property, with an overpotential of only 235 mV (10 mA/cm²). Compared with Fe₁Co₃ MAs or Mo_0.3Fe₁Co₃ MAs, density functional theory (DFT) demonstrated that the better catalytic capacity of Mo_0.3Fe₁Co₃–Se MAs is attributed to the doping of Mo species and selenization lowers the energy barrier for the ^*OOH to O₂ step in the OER process. Excellent OER performance ensures the self-oxygenation in this system, avoiding the addition of air or oxygen in the traditional electro-Fenton process. For the cathode, Mo doping can lead to the lattice contraction and metallic character of CoSe₂, which is beneficial to accelerate electron transfer. The adjacent Co active sites effectively adsorb ^*OOH and inhibit the breakage of the O–O bond. Rotating ring disk electrode (RRDE) test indicated that Mo_0.3Fe₁Co₃–Se MAs has an excellent 2e⁻ ORR activity with H₂O₂ selectivity up to 88%, and the generated H₂O₂ is activated by the adjacent Fe site through heterogeneous Fenton process to generate ·OH.

A novel Ni doped carbon quantum dots (Ni-CQDs) fluorescence probe was synthesized by facile electrolysis of monoatomic Ni dispersed porous carbon (Ni–N–C). The obtained Ni-CQDs showed a high quantum yield of 6.3% with the strongest excitation and emission peaks of 360 nm and 460 nm, and maintained over 90% of the maximum fluorescence intensity in a wide pH range of 3–12. The metal ions detectability of Ni-CQDs was enhanced by Ni doping and functional groups modification, and the rapid and selective detection of Fe³⁺ and Cu²⁺ ions was achieved with Ni-CQDs through dynamic and static quenching mechanism, respectively. On one hand, the energy band gap of Ni-CQDs was regulated by Ni doping, so that excited electrons in Ni-CQDs were able to transfer to Fe³⁺ easily. On the other hand, the abundant functional groups promoted the generation of static quenching complexation between Cu²⁺ and Ni-CQDs. In metal ions detection, the linear quantitation range of Fe³⁺ and Cu²⁺ were 100–1000 μM (R² = 0.9955) and 300–900 μM (R² = 0.9978), respectively. The limits of detection (LOD) were calculated as 10.17 and 7.88 μM, respectively. Moreover, the fluorescence quenched by Cu²⁺ could be recovered by EDTA²⁻ due to the destruction of the static quenching complexation. In this way, Ni-CQDs showed the ability to identify the two metal ions to a certain degree under the condition of Fe³⁺ and Cu²⁺ coexistent. This work paves the way of facile multiple metal ion detection with high sensitivity.

To enhance the catalytic activity by designing metal particles combined with atomically dispersed non-noble metal catalyst is a huge challenge, which yet has not been studied widely in organic reactions. Herein, we describe a simple and efficient method to synthesize Fe_xC combined with Fe single atoms anchored on the N-doped porous carbon by regulating pyrolysis temperature. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and extended X-ray absorption fine structure (EXAFS) spectroscopy corroborate the existence of atomically dispersed Fe and the coordination number between Fe and N atoms. The Fe–N–C-800 catalyst exhibits the highest catalytic activity giving the 97% yield of quinoline in dehydration of 1,2,3,4-tetrahydroquinoline (THQ) reaction at a mild condition (60 ℃, O₂ balloon), and it shows good stability with 80% isolated yield after five consecutive dehydration reactions. Moreover, density functional theory (DFT) calculations reveal that coexistence of Fe_xC and FeN_x structure exhibits high activity owing to the lowest adsorption energy of co-adsorbed O₂ and THQ and the longest N–H bond length of THQ, that is because the existence of Fe_xC induces the charges transfer. Our work may open a new route to design metal particles combined with atomically dispersed non-noble metal catalysts with high activity in organic synthesis.