Effects of Oxygen Vacancies with Different Valence States on the Photo(electro)catalytic Performance of a 2D TiO2:N (001) System

The effect of different valence states Vo on the photo(electro)catalytic performance of the 2D TiO2:N system was investigated using the GGA+U method with first principles. In the poor oxygen conditions, the Ef values of 2D Ti24O46N (Vo0/Vo1+/Vo2+) systems are all less than zero, and all of them are exothermic. Photocatalytic investigations revealed that among the 2D Ti24O46N (Vo1+), 2D Ti24O46N (Vo2+), and 2D Ti24O46N (Vo0) systems, the 2D Ti24O46N (Vo0) system has the best carrier activity, the longest electron–hole lifetime, prominent visible light, infrared light redshift, and outstanding oxidation ability. The photocatalytic decomposition of water and oxygen evolution is highly advantageous. Electrocatalytic studies showed that compared with the free energy of 2D Ti24O46N (Vo1+) and 2D Ti24O46N (Vo2+) systems the free energy ΔGH* of the 2D Ti24O46N (Vo0) system is −0.156 eV and the smallest, which is conducive to hydrogen evolution. The overpotential of the oxygen evolution reaction is 0.360 V, which is close to zero, and the four reaction processes are all downward, indicating that the OER reaction can be driven independently by the photogenerated holes, which is conducive to the electrocatalytic reaction. Moreover, the ability of decomposing water is relatively good. The 2D Ti24O46N (Vo0) system is a candidate nanomaterial and can be applied as a novel photoelectric catalyst.