In situ oxygen doped Ti3C2Tx MXene flexible film as supercapacitor electrode

Heteroatom doping has been proven to be an effective strategy to improve the electrochemical energy storage capacity of two-dimensional MXenes. However, the heteroatom for MXenes is mainly focused on the N atoms, while the effects and underlying mechanisms of O substituted partial C atoms of MXene have not been explored so far. Herein, comprehensive research is firstly performed to reveal the oxygen doping mechanism in Ti3C2Tx MXene by the experimental characterization and the density functional theory simulation. The in situ oxygen doped Ti3C2Tx nanosheets, in which oxygen atoms substitute partial carbon atoms in the titanium octahedron, are synthesized by etching the oxygen doped Ti3AlC2 MAX phase, which is more facile than the complex postdoped process. The introduction of appropriate oxygen atoms can effectively improve the interlayer space, electronic conductivity, and interface charge transfer of the Ti3C2Tx MXene as a supercapacitor electrode. Further, the electrochemical performances demonstrate that the oxygen doped MXene (O-Ti3C2Tx-0.05) film electrode can deliver a higher capacity of 306.0 C g-1 compared to the pristine Ti3C2Tx electrode (216.8 C g-1). Besides, the quantitative analysis results imply that the enhanced capacitance is mainly attributed to the diffusion-controlled capacitance and interface capacitance, which result from the higher Ti metal active center, the enhanced quantum capacitance, and the higher adsorption energy.