Improvement of Noble Metal Based Photocatalysts by Spray Pyrolysis Processes

Abstract

Oxidation technologies and advanced oxidation processes (AOPs) have been regarded as a competitive method for the remediation of persistent pollutants in water. Among AOPs, the use of photocatalysis has particularly attracted interest in recent decades. However, attempts to improve the effi ciency of photocatalysts in terms of both enhanced activity and applicability under visible light have proved challenging. In this context, there is a need for processes able to achieve the synthesis of innovative nanostructured materials meeting these criteria with reproducibility and scalability in mind. The aim of this review is to focus on two themes of interest, namely noble metal based catalysts and spray pyrolysis (SP) processes. Several alternative SP methods have been reported and these will be described. The emphasis is placed on the recent use of SP for the synthesis of noble metal/ semiconductor nanomaterials and their enhanced photocatalytic activity. Recent innovations in the design of SP processes and their potential to further improve noble metal-based photocatalysts are also examined. Finally, the possibility of using SP processes as a fl exible tool to achieve immobilisation of photocatalysts onto substrates and in reactor for real water treatment application is considered.

Preparation of Bifunctional CuWO4‐Based Heterostructure Nanocomposites for Noble‐Metal‐Free Photocatalysts

“…A similar result was reported for the preparation of Ni doped SnO 2 nanorods by wet chemical method in the presence of PEG. [34] It is obviously visible from the FTIR analysis that the intensity, band position and width of the vibrational bands are changed with annealing temperatures due to the variation in grain size, morphology and formation of CuO, Cu 2 O and WO 3 /CuO nanocomposites are confirmed. Further, the formation of homo-and heterojunction in these nanocomposites are picturelly evidenced by HRTEM ( Figure 8) and selected area electron diffraction (SAED) analysis ( Figure S3).…”

“…The heterostructured nanocomposite is a single material obtained by the integration of either two or more semiconductor nanomaterials . In order to prepare heterostructured nanocomposite, two or more‐steps needed for incorporation of another semiconductor as co‐catalyst on the surface of the bare photocatalyst or shell formation to cover the bare photocatalyst . In the heterostructure, interconnection between the photocatalyst and co‐catalyst plays a key role in the reduction of electron‐hole pair recombination.…”

“…[1,2] In order to prepare heterostructured nanocomposite, two or more-steps needed for incorporation of another semiconductor as co-catalyst on the surface of the bare photocatalyst or shell formation to cover the bare photocatalyst. [3][4][5][6] In the heterostructure, interconnec-tion between the photocatalyst and co-catalyst plays a key role in the reduction of electron-hole pair recombination. In recent years, some noval photocatalysts such as CuWO 4 , CoWO 4 and Ag 2 WO 4 based heterostructured nanocomposites have been reported with imporved photocatalytic activity.…”

“…[10][11][12][13][14] Copper (Cu)-based co-catalysts (Cu, Cu(OH) 2 , Cu 2 O, CuO) have deserved a special attention in the oxidation of organic pollutants and photocatalytic hydrogen production. [13,14,[15][16][17][18] Cu-based ternary oxides (CuWO 4 , CuRhO 2 , CuRh 2 O 4 , CuN-bO 3 , CuNb 2 O 6 and Cu 3 VO 4 ) are stable photocatalyst from neutral to basic condition of aqueous electrolyte. [5,[19][20][21][22][23][24] During the particle synthesis, island-like nanosized or a thin layer of copper oxide (CuO) was inevictably produced on the surface of the ternary oxides.…”

“…The CuO is a stable photocatalyst. Chen and Xu have been reported that the heterostuctured CuWO 4 /WO 3 and CuWO 4 /CuO nanocomposites formed by annealing the hydrothermally as-prepared particles. [19] They showed more photocatalytic activity and photocurrent generation than the both bare photocatalysts and physically prepared nanocomposites.…”