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MXenes with unique physical and chemical properties have been extensively applied in various energy storage systems. Nevertheless, the limited capacity and instability of MXene hamper its practical applications in alkali-ion batteries. Herein, for the first time, V2CTx MXene is rationally converted into VS4-carbon composite, which is strategically engineered with a hollow morphological configuration and an integrated reduced graphene oxide (rGO) layer. Regarding potassium storage, the as-designed hollow VS4/C/rGO composite shows a capacity of 549 mA h/g at 0.1 A/g and durable cyclic behavior exceeding 2000 cycles at 1 A/g. What's more, this composite displays a remarkable capacity of 202 mA h/g at a high rate of 20 A/g, surpassing most V-based and MXene-based anodes. For sodium storage, it also manifests exceptional rate capability and long-term cycling life. As disclosed by kinetics analysis and ex-situ characterizations, the unique merits of the hollow structure, small VS4 particles, and protective rGO coating are desirable for the good structural stability and fast charge transportation, thus accounting for the excellent battery performance of the V2CTx-derived hollow VS4/C/rGO composite. [ABSTRACT FROM AUTHOR]

One of the most promising methods for capturing carbon dioxide (CO2) is solid physical adsorption, which is an efficient and simple technique. The key to effective CO2 capture is the development of high-performance solid adsorbents with excellent CO2 adsorption capacity, CO2/N2 selectivity, and rapid adsorption/desorption kinetics. In this paper, a Mg-MOF-74/sodium alginate composite aerogel was prepared by loading Mg-MOF-74 on sodium alginate sheets followed by directional freeze-drying. The composite aerogel exhibited a hierarchical porous structure, in which sodium alginate provided an open mesoporous/macroporous structure that promoted diffusion and contact with the active center of CO2. The Mg-MOF-74 micropores/mesopores promoted the strong interaction between CO2 and the adsorbent in the micropore and rapid mass transfer of CO2 to the adsorbent through the mesopores. The experimental data showed that MSA-6 achieved CO2 adsorption of 2.461 mmol·g–1 at 298 K. Furthermore, the CO2/N2 adsorption selectivity of MSA-6 reached 35.108, indicating its strong CO2 selective adsorption potential. [ABSTRACT FROM AUTHOR]