Covalent alteration of Ti3C2Tx MXene layers by selenium decoration for enhanced electrochemical capacitance

Covalent surface modification of two-dimensional nanomaterials, such as MXene, is a crucial technique to tune the properties of such nanomaterials. Ti3C2Tx with semi-metallic selenium (Se) atoms has been rationally designed and successfully synthesized by facile solid-state chemistry. The electrochemical capacitance of the synthesized pristine Ti3C2Tx and Se/Ti3C2Tx has been assessed basis on assembled symmetric and asymmetric supercapacitors with 1 M Na2SO4 neutral electrolyte. The Se/Ti3C2Tx supercapacitor exhibited a high specific capacitance of 96 F g−1, which is about 53 % higher than the synthesized Ti3C2Tx. Furthermore, a high areal capacitance (485.97 mF cm−2), very good energy density (30 Wh kg−1) and power density (124.7 W kg−1), as well as cycling stability (~90 % capacitance retention over 3000 cycles) were obtained for the Se/Ti3C2Tx supercapacitor. These enhancements are attributed to the larger specific surface area, the reduction of fluorine content, and charge polarization imposed by the TiSe2 binding sites. The asymmetric integrated supercapacitor also not only delivered a good capacitive performance but also demonstrated very high energy and power densities in comparison with the pristine Ti3C2Tx nanosheets.