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2D MXenes (transition metal carbides, Ti 3 C 2 T x) with large surface area and metallic conductivity are widely used as supporters in catalysts. Unfortunately, the single MXene sheets would deteriorate in the presence of oxygen and water, which is almost the same as the environment of oxygen reduction reaction (ORR). Herein, an "armor" was constructed to encapsulate the oxidizable MXene by a confined in-situ oxidative polymerization strategy, employing the electrostatic interaction between the exfoliated MXene sheets (negatively charged) and oxidant (Fe3+, positively charged). The ultra-dispersed binary Fe 3 N and Co sits coupled with the large surface area MXene supporter synergy to endow more exposed active sites, meanwhile, the density functional theory (DFT) studies reveal that a moderate binding strength between the intermediates and the binary active sites was effectively modulated to enhance the ORR performance. The synthesized Fe 3 N/Co–N–C@MXene exhibits an impressive half-wave potential (E 1/2 , 0.871V) and a lower Tafel slope of 52.56 mV dec−1 than that of Pt–C-20% (74.89 mV dec−1). The Fe 3 N/Co–N–C@MXene based ZAB exhibits a four times higher peak power density (189.16 mW cm−2) than the Pt–C-20% based ZABs and superior cycle stability within 320 h. Furthermore, the assembled flexible ZABs shows high flexibility and stability in different bending scenarios. [Display omitted] • Ultra dispersion binary Fe 3 N/Co–N–C encapsulated MXene composites for ORR. • Large surface area and uniformly distributed active sites synergize for a high-performance ORR catalyst. • About four times higher peak power density (189.16 mW cm−2) than that of Pt–C-20%. • High-stability zinc-air battery with a voltage gap merely increased by 36 mV in 320 h. • High flexible zinc-air battery for different bending scenarios. [ABSTRACT FROM AUTHOR]

The seeking of the intrinsically ferromagnetic materials has been extended to the two-dimensional transition metal carbide MXene in recent years. However, as the first synthesized member in this family, the experimental study of the magnetism on Ti 3 C 2 T x is rare. Herein, monolayer MXene Ti 3 C 2 T x was prepared by LiF/HCl etching method and annealed in H 2. The magnetic properties of the as-prepared and annealed Ti 3 C 2 T x were investigated. The results show that the as-prepared Ti 3 C 2 T x exhibits the very weak paramagnetism. After H 2 annealing, the significant enhancement in the saturation magnetization is observed, and the ferromagnetism appears after annealing at 500 °C. Density functional theory simulations show that Ti–C vacancy pairs created during the exfoliation and H 2 annealing are the major magnetic sources. Image 1 [ABSTRACT FROM AUTHOR]