Surface modification or doping of WO3 for enhancing the photocatalytic degradation of organic pollutant containing wastewaters: A review
Journal
Materials Science Forum
Journal Volume
855
Pages
105-126
Date Issued
2016
Author(s)
Abstract
Tungsten trioxide (WO3) is an oxygen deficient metal oxide and well known semiconductor with a small band gap of between 2.4 and 2.8 eV. It is also used as a photo-catalyst for degradation of organic pollutants present in aqueous environment. It has stable physicochemical properties and shows strong absorption of solar spectrum and thus can be used in visiblelight driven photocatalysis. WO3 has a conduction band (ECB) of +0.4 V versus NHE (normal hydrogen electrode) at pH = 0. Therefore, pure WO3 has lower light energy conversion efficiency as compared to other widely used photocatalysts such as zinc oxide (ZnO) and titanium oxide (TiO2). This is because the reduction potential of the electrons in WO3 is low due to its low conduction band level. O2 cannot be efficiently trapped in the conduction band electrons to yield superoxide radicals and fast recombination of charge carriers takes place resulting in lesser photocatalytic activity of WO3. However, holes in the valence band (EVB = +3.1 V) are energetically favorably situated to oxidize water to hydrogen. To modify the energy band position and reduce the charge carrier recombination, doping or surface modification of WO3 is necessary. This review article demonstrates the effect of dopants (low band semiconductor catalyst) on the surface modification of WO3 to enhance the photo catalytic activity which helps in degradation of the organic pollutants present in the wastewater.
SDGs
Type
conference paper