Photoinduced Supercapacitance and Photocatalytic Performance of TiO2 Enhanced by Electronic Band Structure Modification Using Cu-doping

Abstract

We demonstrate that doping a modest quantity of Cu impurity into anatase TiO2 significantly enhances its photoinduced electrocatalytic supercapacitance by about 84% and its photocatalytic activity by more than twofold. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy analyses validate that the Cu dopant is fully incorporated into the tetragonal crystal structure of the host material and creates Ti3+ and oxygen vacancies. Furthermore, UV-vis spectroscopy and photoluminescence (PL) studies demonstrate that the smallest optical band gap energy (Eb) of 2.85 eV and minimal recombination of photoinduced charge carrier pairs occur at a 3% Cu doping amount. Transmission electron microscopy (TEM) images reveal that pristine TiO2 and Cu-doped TiO2 exhibit nearly identical pebble-like nanoparticle morphologies. This 3% Cu-doped TiO2 demonstrates more than double photodegradation (95.7%; 150 min) of a toxic Rhodamine B dye molecule and a nearly 84% improved supercapacitance (347 F/g; 0.5 M aq. Na2SO4; pH=7) than that of a pristine anatase TiO2. In suitable testing conditions of other electrolytes, molecular dyes, light intensity, etc., Cu-doped TiO₂ with different particle shapes may demonstrate even greater supercapacitive behavior and photodissociation properties, leading to more advantageous applications for photoactive Cu-doped TiO₂ materials.