The important role of oxygen defect for NO gas-sensing behavior of α-Fe2O3 (0 0 1) surface: Predicted by density functional theory

Abstract

Using density functional theory (DFT), we investigated and discussed the adsorption characteristics, gas-sensing response and gas-sensing mechanism of NO molecule on α-Fe2O3 (0 0 1) surface with and without oxygen defect (VO). The pure and oxygen-defective α-Fe2O3 (0 0 1) surface exhibited opposite electron transfer. The theoretical results proved that the NO molecule acted as a donor for pure α-Fe2O3 (0 0 1) surface. However, it failed to explain the increasing resistance of n-type metal oxide materials. For oxygen-defective α-Fe2O3 (0 0 1) surface, NO molecule acted as an acceptor. The results leaded to a decreasing electron-carrier concentration, and then resulted in an increasing resistance of oxygen-defective α-Fe2O3 (0 0 1) surface after NO molecule was introduced into. The direction of electron transfer was reversed by oxygen defect. In addition, the VO-NO adsorption configuration induced more stable adsorption structure and more significant electron transfer effects between NO molecule and oxygen-defective α-Fe2O3 (0 0 1) surface. The VO-NO adsorption configuration would have better gas-sensing performance for α-Fe2O3 (0 0 1) surface.