Single-atom catalysts possess attractive electrocatalytic ability for degrading contaminants owing to their desirable characteristics compared with bulk counterparts. Herein, single Cu atoms anchored on Ti₃C₂T_x MXene (Cu-SA/Ti₃C₂T_x) have been demonstrated as a highly reactive and robust nanohybrid filter for ultrafast removal of micropollutants via electro-peroxymonosulfate (PMS) activation. Sulfamethoxazole, a typical antibiotic, is observed to fully degrade via a single-pass through the nanohybrid filter (<150 ms) at 1.5 mL min⁻¹. Both experimental and theoretical studies verified that the Cu–O₃ are the active sites for electro-PMS activation to produce ¹O₂ and induce electron transfer for SMX degradation. As a result of the size effects, the HO˙ radicals dominate the SMX degradation process when anchoring Cu nanoparticles to the Ti₃C₂T_x nanosheets. This study provides a proof-in-concept demonstration of the free-standing Cu-SA/Ti₃C₂T_x nanohybrid filter that may find important applications in addressing the global problem of water pollution.

As one of the most important subjects in chemistry, nitrogen activation and reduction to yield ammonia is still a big challenge. The lack of deep understanding of the nitrogen reduction reaction (NRR) impedes the development of high-performance catalysts. In the present study, we introduce a second transition metal (M = Mn, Fe, Co, Ni, Cu, Zn, and Mo) into the active site of a single-atom Fe–N–C catalyst to tune the electronic structure and study the activity of the as-designed neighboring bimetal Fe/M–N–C catalyst in the electrochemical NRR under acidic conditions, by performing first-principles calculations. By checking the stability of the catalysts, the adsorption ability for N₂, the Gibbs free energy change for the potential-determining step in the NRR, and the hydrogen evolution reaction (HER) activity, only the Fe/Mn–N–C catalyst is predicted to be a promising candidate for the NRR as it shows significantly improved catalytic activity and strong selectivity against the HER. A mechanistic study reveals the synergistic effects of the bimetal active sites, and the introduced Mn atom generates a strong multi-reference effect on the electronic configuration to create more tunnels to transfer the d-orbital electrons to activate the inert NN triple bond, inducing the “acceptance–donation” process to facilitate the activation and reduction of N₂. The current results provide an effective strategy to design stable, active, and selective catalysts for the electrochemical NRR.