Acetone sensitivity and quantum capacitance of novel modified TiO₂ nanosheet: A DFT investigation

Abstract Despite being relatively new to 2D nanoworld, TiO 2 nanosheets (TiO 2 NS) are rapidly gaining prominence as highly effective materials for chemical sensor, photocatalysis and electrochemical energy storage. In this study, the potential of density functional theory employ to thoroughly investigate how defects and dopants influence the physical properties of TiO 2 nanosheets (TiO 2 NS). Our research aims to reveal the fascinating interactions that occur between both pristine and defective lepidocrocite-type TiO 2 nanosheets when exposed to acetone molecules. Furthermore, we are eager to explore the compelling concept of quantum capacitance in the defected and doped nanosheets, opening new avenues for innovation in material science. The TiO 2 NS having an energy band gap of 3.48 eV, exhibits new impurity state near the Fermi level on incorporation of oxygen or titanium vacancy (O V or Ti V ). These states in the O V (1)/Ti V (3)- TiO 2 NS play an important role in holding acetone molecules with adsorption energies (E ads ) of −2.37 eV/–1.83 eV. Various electronic analyses, including Mulliken population, inter-frontier orbital, and electron difference density (EDD) plots, all point to an apparent dispersion of electronic charge from acetone to the O V (1)/Ti V (3)-TiO 2 NS. Contrary to these findings the pristine and O V (2)-TiO 2 nanosheets weakly hold the acetone molecule. Engineering the surface morphology of TiO 2 NS either by creating O V /Ti V defect or N/Sc/V doping results in robust quantum capacitance appearing in the electrolytic range of −1.00 V to 1.00 V. Titanium deficient TiO 2 NS has wide spread large C Q spectra with C Qmax and Q max of 1198 μF cm −2 and 512 μC cm −2 ; respectively. The O V (1)/O V (2)- TiO 2 NS shows low intense C Q peaks in negative voltage region. Doping with N, Sc, and V has a profound impact on the quantum capacitance of TiO 2 NS. In particular, Sc doping introduces remarkable C Q spectra in the positive region. This demonstrates that defected and doped TiO 2 NS holds great promise for applications in acetone sensing and energy storage devices.