Functionalization and Defect-Driven Water Splitting Mechanism on a Quasi-Two-Dimensional TiO2 Hexagonal Nanosheet

Abstract

In this work, we have dealt with the functionalization of a newly reported quasi-2D hexagonal nanosheet (HNS) of titanium dioxide (TiO2) for photocatalytic water splitting to generate hydrogen and oxygen. Functionalization has been carried out by creating a single oxygen vacancy defect as well as by incorporating substitutional doping with C, N, P, and S atoms at the O site of TiO2 HNS. The effects of functionalization and vacancy defects on the structural and electronic properties of HNS have been investigated by determining the corresponding projected density of states. It has been observed that functionalization causes a shift in the VBM and CBM of HNS, which in principle influences the catalytic activity. In addition, we have determined the work function for these materials in order to correlate them with the electrochemical activities of different considered HNSs. The catalytic activity has been predicted by determining the reaction coordinate as constructed from the free energies of the different reaction intermediates involved in HER and OER. Among all of the systems that we have studied, HNS with an oxygen monovacancy has emerged as the best possible candidate for the water-splitting mechanism. © 2019 American Chemical Society.