Oxygen Vacant Semiconductor Photocatalysts

Abstract

Semiconductor photocatalysis acts as a sustainable green technology to convert solar energy for environmental purification and production of renewable energy. However, the current photocatalysts suffer from inefficient photoabsorption, rapid recombination of photogenerated electrons and holes, and inadequate surface reactive sites. Introduction of oxygen vacancies (OVs) in photocatalysts has been demonstrated to be an efficacious strategy to solve these issues and improve photocatalytic efficiency. This review systematically summarizes the recent progress in the oxygen vacant semiconductor photocatalysts. Firstly, the formation and characterizations of OVs in semiconductor photocatalysts are briefly introduced. Then, highlighted are the roles of OVs in the photocatalytic reactions of three types of typical oxygencontaining semiconductors, including metal oxides (TiO 2 , ZnO, WO 3 , W 18 O 49 , MoO 3 , BiO 2-x , SnO 2 , etc), hydroxides (In(OH) 3 , Ln(OH) 3 (Ln=La, Pr, and Nd), Layered double hydroxides) and oxysalts (bismuth-based oxysalts and others) photocatalysts. Moreover, the advanced photocatalytic applications of oxygen vacant semiconductor photocatalysts, such as pollutant removal, H 2 production, CO 2 reduction, N 2 fixation and organic synthesis are systematically summarized. Finally, an overview on the current challenges and a prospective on the future of oxygen vacant materials is proposed.

Light-driven oxygen evolution from water oxidation with immobilised TiO2 engineered for high performance

“…We further have examined the surface chemical states of TiO 2 using XPS spectroscopy. Given that XPS allows investigating the surface atomic constituents, it has been used to characterise the degree of oxygen defect according to the relative element contents, and the intensities and positions of peaks 22 , 23 . Among the defects identified in TiO 2 , the presence of oxygen vacancies (O v ) can act as active adsorption sites, and strongly influence the reactivity of the photocatalysts 22 .…”

“…Given that XPS allows investigating the surface atomic constituents, it has been used to characterise the degree of oxygen defect according to the relative element contents, and the intensities and positions of peaks 22 , 23 . Among the defects identified in TiO 2 , the presence of oxygen vacancies (O v ) can act as active adsorption sites, and strongly influence the reactivity of the photocatalysts 22 . Additionally, the formation of O v commonly leads to the creation of unpaired electrons that can generate donor levels in the electronic structure of the TiO 2 24 , 25 .…”

Light-driven oxygen evolution from water oxidation: TiO2 engineering in the performance of the immobilised photocatalysts

“…We further have examined the surface chemical states of TiO 2 using XPS spectroscopy. Given that XPS allows investigating the surface atomic constituents, it has been used to characterise the degree of oxygen defect according to the relative element contents, and the intensities and positions of peaks 22,23 . Among the defects identi ed in TiO 2 , the presence of oxygen vacancies (O v ) can act as active adsorption sites, and strongly in uence the reactivity of the photocatalysts 22 .…”

“…Given that XPS allows investigating the surface atomic constituents, it has been used to characterise the degree of oxygen defect according to the relative element contents, and the intensities and positions of peaks 22,23 . Among the defects identi ed in TiO 2 , the presence of oxygen vacancies (O v ) can act as active adsorption sites, and strongly in uence the reactivity of the photocatalysts 22 . Additionally, the formation of O v commonly leads to the creation of unpaired electrons that can generate donor levels in the electronic structure of the TiO 2 24,25 .…”

Transformation of Wurtzite ZnO to a New Triclinic Nanoporous ZnO Phase via Hydrothermal Treatment with Metformin for Designing Proton Conducting Material

“…Zinc oxide (ZnO) is a cheap, abundant and versatile semiconductor material, [1,2] which is largely explored in several frontline applications like gas sensors, [3–5] LED display devices, [6] photoelectrodes, [7] ultraviolet photodetectors, [8,9] electrochromism, [10] solar cells, [11] a wide range of heterojunction nanocomposite materials for photocatalysis, [12–14] biomedicine /drug‐delivery, [15] catalysis [16] and so on. The semiconductor and optical properties of the metal oxides can be tuned significantly by modification of crystal phase of the materials [17–19] .…”