Bandgap engineering of oxygen-rich TiO2+x for photocatalyst with enhanced visible-light photocatalytic ability

Abstract

TiO 2 , as a photocatalyst, has attracted substantial attention since the discovery of water splitting property on the TiO 2 electrodes. However, its efficiency of water splitting is limited by its wide bandgap (*3.0 eV). Here, we predict its bandgap can be efficiently reduced by incorporating excess oxygen atoms on the basis of firstprinciples calculations. We show that the excess oxygen is more stable to bond to Ti atom and to form ordered structure. The narrowing of bandgap in oxygen-rich TiO 2 originates from the ordered excess oxygen because the coupling between them shifts the conduction band bottom down. The bandgap of TiO 2?x decreases with the increase of the density of excess oxygen (x). A bandgap of 1.3 eV can be achieved at x = 0.5. The oxygen-rich TiO 2 shows intrinsic semiconducting characteristic without localized states within the bandgap, indicating lower trapping centers. The enhancement of visible-light absorption due to the narrowed bandgap and the intrinsic semiconductor characteristic result in the improvement of the photocatalytic performance in oxygen-rich TiO 2?x .

Electron-assisted synthesis of g-C3N4/MoS2 composite with dual defects for enhanced visible-light-driven photocatalysis

“… 8 A suitable concentration of defects can effectively reduce the recombination rate of electrons and holes, change the band gap structure, and enhance the light absorption capacity. 9 Surface defects may also serve as physical adsorption or chemically active sites to improve photocatalytic reactions. 10 Defect engineering can usually be achieved by chemical reduction method, 11 high-temperature hydrogen reduction, 12 and light reduction.…”

Structural and Electronic Properties of Two-Dimensional Organic–inorganic Halide Perovskites and their Stability against Moisture

“…Finding materials to efficiently harvest solar power has been a challenge to satisfy the increasing demand on energy. Basically, the materials for high efficiency should satisfy the following: (a) optimal bandgap for maximal sun-light absorption, (b) high carrier mobility, and (c) efficient electron–hole separation. − Hybrid organic–inorganic perovskites (HOIPs) have triggered considerable interests due to remarkable photovoltaic efficiency and low cost. , The bulk HOIP (3D HOIP) has a chemical formula of ABX 3 (A = CH 3 NH 3 + (MA + ) or CH­(NH 2 ) + (FA + ); B = Pb 2+ or Sn 2+ ; X = Cl – , Br – , or I – ). The A cation sits at the eight corners of the cubic unit, while the B cation is at the center of an octahedral [BX 6 ] 4– cluster.…”

Synergic effects of Cu O electron transfer co-catalyst and valence band edge control over TiO2 for efficient visible-light photocatalysis

“…Oxygen defects are intrinsic and fundamental defects in TiO2 (and other semiconductor oxides) for bandgap engineering and modifying photoelectric properties [34][35][36][37]. In addition to the use of oxygen-deficient defects in TiO2 for conduction band edge control, oxygen excess defects also offer a way to improve visible-light absorption through valence band edge control, because TiO2 has a sufficiently high photo-oxidizing capacity [38][39][40][41][42]. Etacheri et.…”

“…[40] fabricated oxygen-rich TiO2 nanoparticles with Ti vacancies, which exhibited p-type conduction characteristics and a shifted valence band (VB) edge. Moreover, oxygen-rich TiO2 is highly stable owing to the large energy of formation of oxygen excess defects [41]. Therefore, it is hypothesized that, combining co-catalysts to improve electron transfer and raising the valance band edge by the introduction of oxygen excess defects for visible-light absorption is a potential strategy to enhance the photocatalytic activity of TiO2.…”

“…To date, the main strategies for obtaining oxygen-rich TiO2 have been limited to calcination of peroxo-titania xerogels or solvothermal methods [38][39][40][41]. There is a need to developed simple and high-yield strategies for the fabrication of oxygen-rich TiO2 with favorable particle dispersions and large surface areas.…”