The design of high performance photoanode of CQDs/TiO2/WO3 based on DFT alignment of lattice parameter and energy band, and charge distribution

Abstract

Photoanode is the key issue for photoelectrocatalytic (PEC) water splitting and organics degradation. However, it always faces several restrictions including severe photocorrosion, low charge separation and transfer efficiencies, poor visible light harvesting, and sluggish interfacial reaction kinetics, which often required a variety of modifications with only low improvements achieved. Herein, a high performance CQDs/TiO2/WO3 photoanode was designed on the basis of density function theory (DFT) alignment of lattice parameters and energy band, and charge distribution. The TiO2/WO3 heterojunction can abate photocorrosion through the hetero-epitaxial growth of TiO2 (001) on WO3 (002) for the lattice mismatch <3% eliminating dangling bonds, with high corrosion resistance and photostability of TiO2. As the built-in field constructed by a staggered band alignment structure with the valence band offset (VBO) of 0.51 eV, the photogenerated carriers transfer and separation are promoted dramatically. Through the DFT calculations, the sunlight absorption wavelength can be extended, and the interfacial reaction kinetics can be expedited with the modification of carbon quantum dots (CQDs) on TiO2/WO3, due to the narrower bandgap (Eg) and the accumulation of electrons at TiO2 side. The DFT designed CQDs/TiO2/WO3 photoanode significantly increase photocurrent density from 0.90 to 2.03 mA cm−2 at 1.23 V, charge separation efficiency from 56.3 to 79.2% and charge injection efficiency from 51.2 to 70.4%, and extend light absorption edge from 455 to 463 nm over pristine WO3, with better photostability and lower holes-to-water resistance.