Why DO-DION NP Powders Are Chosen As Photocatalysts
There are many reasons why PdO/TiON NP powders are chosen as a photocatalyst for MTBE mineralization under visible light. These reasons are listed and discussed as follows:
1- The synergistic effect.
2- The ease of synthesis.
3- The memory effect.
4.1 The synergistic effect
Nowadays, modified TiO2 by metal and nitrogen is considered as one of the most promising TiO2 based materials for photocatalytic applications, which is able to harvest a significant amount of solar light. It has not only influences the optical properties, photoreactivity, charge recombination rates, and interfacial electron transfer rates, but also improves the physical properties of TiO2 such as the size of the …show more content…
Nitrogen doping into the lattice TiO2, whether substitutional or interstitial doping can form the localized mid-gap states lying just above the valence band of TiO2, which could narrow the band gap of TiO2 and shift the absorption to the visible region as shown in the figure 1 (the red line). However, metal ion incorporated into the lattice TiO2 can introduce the intra-gab impurity state close to conduction band of TiO2 as shown in the figure 1 (the green line). Both factors work synergistically to make the degradation efficiencies higher than doping with N or single metal under visible light without reducing its activity under UV light. To examine the synergistic effect of different metals on TiON photoactivity, comparative studies were performed between the base metals such as Fe, Cu, Ni, etc. and platinum group metals (PGM) co-doped in TiON to …show more content…
As the size of materials is reduced down into the nanometer scale, the percentage of atoms or ions exposed on the surface will be massively increased in the surface-to-volume ratio. Thus, finding the efficient and non-costly method will be required. Le and co-workers reported ultrafine p-type PdO semiconductor NPs (~2 nm) assembled into n-type TiON thin film by ion-beam-assisted deposition (IBAD) technique to minimize the embedded PdO nanoparticle size to no longer than few nanometers. Consequently, large volumes of PdO nanoparticles in TiON were quickly populated with electrons reducing PdO semiconductor to metallic Pd, creating SPR effect and enhancing visible-light absorption. Although IBAD technique provides an efficient photocatalyst under visible light, it is considered a costly technique and time consuming because it requires specific equipments, specific conditions and multiple steps of synthesis. It is not surprising that more attention is given lately to the reduction of particle size by simpler processes such as so-gel methods, applicable for various sizes, shapes, and formats (e.g., fibers, films, monoliths, and nano-sized particles). Consequently, the synthesis of PdO/TiON NPs by sol-gel method using palladium acetylacetonate (Pd(acac)2) have been reported which provided the crystalline