Two-dimensional vanadium carbide(V2CTx) MXene as supercapacitor electrode in seawater electrolyte

In this study,two-dimensional V2CTx MXene has been prepared by selectively etching Al layers from V2 AlC MAX phase by NaF+HCl etching at 90℃for 72 h and its performance as supercapacitor(SC)electrode were tested using simulating seawater as electrolyte.V2CTx MXene-based electrodes shows a good capacitance of 181.1 F/g,which is in accordance with the volumetric specific capacitance of 317.8 F/cm^3,and with 89.1%capacitance retention even after 5000 cycle.Compared with other MXenes,V2CTx have better electrochemical performance as SC electrode.This work provides an innovative strategy to apply V2CTx MXene as SC electrode in safety and effective seawater electrolyte.

Carbon dioxide adsorption of two-dimensional carbide MXenes

Two-dimensional carbide MXenes(Ti_3C_2T_x and V_2CT_x)were prepared by exfoliating MAX phases(Ti_3AlC_2 and V_2AlC)powders in the solution of sodium fluoride(NaF)and hydrochloric acid(HCl).The specific surface area(SSA)of as-prepared Ti_3C_2T_x was 21 m^2/g,and that of V_2CT_x was 9 m^2/g.After intercalation with dimethylsulfoxide,the SSA of Ti_3C_2T_x was increased to 66 m^2/g;that of V_2CT_x was increased to 19 m^2/g.Their adsorption properties on carbon dioxide(CO_2)were investigated under 0–4 MPa at room temperature(298 K).Intercalated Ti_3C_2T_x had the adsorption capacity of 5.79 mmol/g,which is close to the capacity of many common sorbents.The theoretical capacity of Ti_3C_2T_x with the SSA of 496 m^2/g was up to 44.2 mmol/g.Additionally,due to high pack density,MXenes had very high volume-uptake capacity.The capacity of intercalated Ti_3C_2T_(x )measured in this paper was 502 V·v^(–1).This value is already higher than volume capacity of most known sorbents.These results suggest that MXenes have some advantage features to be researched as novel CO_2 capture materials.

Construction and performance of CdS/MoO_(2)@Mo_(2)C-MXene photocatalyst for H_(2) production

Nowadays,photocatalytic technologies are regarded as promising strategies to solve energy problems,and various photocatalysts have been synthesized and explored.In this paper,a novel CdS/MoO_(2)@Mo_(2)C-MXene photocatalyst for H_(2)production was constructed by a two-step hydrothermal method,where MoO_(2)@Mo_(2)C-MXene acted as a binary co-catalyst.In the first hydrothermal step,MoO_(2)crystals with an egged shape grew on the surface of two-dimensional(2D)Mo_(2)C MXene via an oxidation process in HCl aqueous solution.In the second hydrothermal step,CdS nanorods were uniformly assembled on the surface of MoO_(2)@Mo_(2)C-MXene in ethylenediamine with an inorganic cadmium source and organic sulfur source.The CdS/MoO_(2)@Mo_(2)C-MXene composite with MoO_(2)@Mo_(2)C-MXene of 5 wt%exhibits an ultrahigh visible-light photocatalytic H_(2)production activity of 22,672μmol/(g·h),which is~21%higher than that of CdS/Mo_(2)C-MXene.In the CdS/MoO_(2)@Mo_(2)C-MXene composite,the MoO_(2)with metallic nature separates CdS and Mo_(2)C MXene,which acts as an electron-transport bridge between CdS and Mo_(2)C MXene to accelerate the photoinduced electron transferring.Moreover,the energy band structure of CdS was changed by MoO_(2)@Mo_(2)C-MXene to suppress the recombination of photogenerated carriers.This novel compound delivers upgraded photocatalytic H_(2)evolution performance and a new pathway of preparing the low-cost photocatalyst to solve energy problems in the future.